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Customer Discussions > Photography forum

choosing a birding camera system (DSLR brands or m4/3), significance of DxOMark, and best lens brand


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Initial post: Oct 13, 2012, 7:16:31 AM PDT
Last edited by the author on Oct 13, 2012, 7:25:04 AM PDT
W.S. says:
Hello,

This may end up being a moderate epistle for assistance in choosing a camera system, so please bare with me.

I have had some interest in photography for several years now. In 2003, I had purchased a Olympus C-5050 and used it extensively while living overseas, in Micronesia. I had purchased an underwater housing from Ikelite and fell in love underwater photography. After I returned to the States, I returned to college and then professional school, which took most of my time. Now that I have been out of school for several years, I have found myself wanting to start photography again. Unfortunately, my underwater housing leaked last year and ruined my C-5050, so no more camera (I don't miss the camera). My wife lets me barrow her old Canon PowerShot SD630 and, if I am lucky, I use her new PowerShot Sx220 HS. I have handled a Nikon D7000, D3200, 1 J1, Panasonic DMC-GH2, Canon 5d MkII, T3i, and Sony SLT-A55?, NEX-3, and at my work we have a Canon Rebel Xti with the battery extension.

One big frustration I had with the C-5050 was the delay in the live view between shots. I remember having some great opportunities diving with manta rays and taking a shot, then the manta was gone by the time I could take the next one. Not only that, the delay between depressing the button and the lag between the shutter, often times caused the moment to be lost. Well, that was nearly ten years ago, so I assume most anything would be better now. Two reason's I went with the C-5050 instead of a DSLR was the size/weight and the video capabilities. I, unfortunately, never really took the time to try and figure out all the buttons on the camera, which may have affected my shots.

I was on Safari in South Africa last year, and was really kicking myself for not just buying a DSLR or m4/3 for the trip. The wildlife and birding was amazing. A friend had some model of the NEX, and it seemed rather slow between shots and I hated the idea of the live view, however, he seemed to really like it. The SD 630 I had was mostly a disappointment in ergonomics, picture quality, reach, and enjoyment, the Sx220 was an improvement, but not by much, better reach and picture quality. My in-laws had the 5dMkII, and I loved shooting with this camera. However, the lens was not satisfactory for reaching some of the wildlife, especially birds, and I used it briefly, while we were in the car, so I am not sure on the portability, layout, and menus. The ergonomics, the image quality, and overall enjoyment were high. There is something about holding the DSLR and shooting it that made it pleasurable for me, there seems to by an inner boy that thinks he is on a shooting range or something. Anyway, I liked it, especially hearing and seeing the shutter go so quickly, no logic behind this.

As for the Nikons, I handled them briefly and liked the D7000's sturdiness, but didn't like either of the DSLR button layouts, same for the A55?. Since I could spend more time with the Xti, I grew fond of the button layout, and most everything on it, the battery extension and hand strap made it more comfortable for me, and all the buttons seemed easily accessed by my right hand, so my left could zoom in and out/focus. I have large hands so I found this to by my favorite, most recently. I barrowed it and set up a bird feeding station in my back yard a few weeks ago, the only lens I had was a 60mm macro, so it couldn't reach the shy birds, I ended up using the Sx220. On the Sc220, I used a cheap tripod, and I fiddled with the ISO and shutter speeds to see if I could get some shots, but they didn't turn out very well, due to low light in the jungle and slow shooting speed.

So, where to go from here. I have looked over multiple websites for the last few weeks and, from my understanding, for birding, I need greater then 5 fps, over 1000 ISO, moderate-high pixels, and full frame if possible. Most importantly, I need a system that has great glass, with stabilization, and reach. This seems to be the hardest thing to find good comparisons on. I understand for birding I need over 300mm lenses, zoom or prime, w/ as large as financially feasible aperture.

At one point I was planning on going with the Canon DSLR system, due to my experience with the Xti. I was debating getting a new/used/refurbished 7d or used/refurbished 1d#, and putting most of my budget (around $3-3.5k USD) into lenses. Then I was reading reviews and noticed that the button layout on the mid/high end Canon's is like the Nikon and Sony, not like the Xti, so no free left hand. This was one wrench in the gears, then came along building a excel spreadsheet with all the specs that mattered to me on most Nikon, Canon, and qualifying m4/3rds, which was ok, until I found DxOMark, which has currently thrown me for a curve. I see that the 7, 5, and 1d's are lower on sports and low light, and the overall rating, compared to the Nikon midlevels. Well, I would like to say I fully understand their rating system, but I don't. One Amazon forum commentator tried comparing it to cars and said that it is like rating the stroke volume of an engine and not including whole system for overall performance... kind of helped... but still having some issues grasping it all, cause I kind of want there to be a problem with the ratings. Moreover, I read some comments on forums by R.N. Clark, in regards to some of the things that DxoMark overlooked, and read some of his articles at http://www.clarkvision.com, but it was somewhat over my head. It has been sometime since college physics, and so I feel like I need to re-read some of them to fully comprehend them. Now, I am at a quandary. I was hoping to have an idea before November so I could take advantage of November sales, but I may have to wait. Part of me is sold on Canon, but, specs are specs, and I am sure I can get used to the Nikon system, but I am not as familiar with it as the Canon, due to the time I have spent looking into it. Plus, Canon seems more intuitive then the Nikon, from first glance. Also, I am considering waiting for the 7d, if I go canon, cause the price should go down with the 7dMkII in Early 2013, but I may be going on a birding trip in late November, so I may need to get one before then.

Another issue is, I am concerned about having to much gear and to much weight. I have no way to handle any of these products until December, due to me living overseas, and I remember not taking my c-5050 on hikes cause I thought it was to much weight, partially due to the poor results/effort ratio. I have looked into the lighter micro 4/3 (m4/3) systems and am impressed with Olympus OM-D E-M5 and the Panasonic DMC-GH2. I have handled the 1 J1, NEX-3, and GF3. The GF3 is way to small, and I could deal with the NEX-3 and the 1 J1, if needed. I am impressed with the GH2's handling and most everything about it. My friend that uses it gets really great photographs underwater and with most everything else. However, he admits there are some AF-tracking issues, which is an issue on the E-M5 also, from what I understand (For overall looks, which don't matter, I like the E-M5 with the silver). Now since I will be needing this for bird photography, the m4/3 AF-tracking issue may be a critical hit, also I am afraid that the shooting lag, might cause me to loose my bird/subject (fear from my experience with the c-5050) and I don't like live view either. It is just really hard to make a decision without actually using the items for some period of time, but my location makes it impossible. Even when I am in the states in December, I will only get to handle them at the store, most likely, without and birds or proper lenses. I almost feel like getting a few options and flipping a coin, but I really don't want to do this.

So in summary, I would like to focus on birding, but would like it if I could have some versatility for wildlife, butterflies, nature, scenery, micro... and most everything else in photography, with adequate video. In addition, I need weather sealing due to the tropical climate I live in. However, I know I can't have it all, especially with my budget. If there was no birding, I would seriously consider a m4/3s, for the size, weight, and versatility, especially the GH2 or the new GH3. If I go with the DSLR, I would really like a full frame, for better light gathering and less noise, and feel willing to get a used/refurbished camera (I found some extended warranties on B&H from Mack) and sacrifice video if needed. The older 1d#'s were looking nice on the specs. I think the 5d mk II will be to slow, leaving the 7d or 5dmkIII as the main new Canon contender. I am still not fully familiar with the Nikon, but, as I recall, the D7000 was the main contender for my budget, although the D800 seems nice on the DxoMark. I briefly considered the Sony DSLR and m4/3 due to the Konica/Minolta glass history and the Zeiss, but am hesitant, due to it not being the top camera leaders, as Nikon and Canon are. I don't want to invest into a system and have to change over. I anticipate being able to invest about $1k per year into the system, unless I get good at it and people want to buy my work, then I could invest more.

I would appreciate any insight into the following: regarding some published side by side brand comparisons between similar DSLR telephoto (zoom and prime) lenses (so I don't have to go and enter all the various ratings on my own, in hopes this will help me decide between brands from the available glass), whether I should buy into DxOMark ratings, disregard, or just consider them, can and will the m4/3 get to the point of being able to bird well and have adequate AF and response, is anyone successful with birding and m4/3rds (if so, what system), are the Mack used warranties safe, should I consider other brands besides Nikon and Canon DSLRs (even though they seem to be the most recommended due to availability of telephoto glass and are market leaders)?

Well, thanks for your time. If I am asking something that has been repeated extensively before, my apologies. If you would be kind enough to share a link, I will be glad to read it, but appreciate any comments, guidance, experience, and suggestions.

Cheers,

Posted on Oct 13, 2012, 8:55:52 AM PDT
brad-man says:
You may want to hold off on deciding until the Canon 6D is released...

In reply to an earlier post on Oct 13, 2012, 9:15:04 AM PDT
T. Campbell says:
The button layouts on most mid to high end DSLRs are designed for one-handed operation while shooting. All of the controls you would use WHILE shooting are on the right. There are buttons on the left, but you generally would not use them while shooting. E.g. they get you to the camera menu, let you review previously taken shots, etc. But you wouldn't do any of those things WHILE shooting, so it's not important that they be on the right. By putting them on the left, it makes more room for controls on the right that you would use while shooting.

In Canon, the mid-level and pro-level bodies are a little different in terms of the major organization of the camera controls.

On a Rebel, there's only one "wheel" on the camera and it's located near the shutter button. So, for example, if you are in "manual" mode, turning the wheel normally adjusts the shutter speed. To adjust the aperture you have to hold the Av button with your thumb while turning that same wheel.

On a mid level or higher Canon (e.g. 60D, 7D, 5D 1D) there are two wheels (or dials). One is still at the front where your index finger can operate it (same as the Rebel) but the second is on the back and is strategically located in a spot where your thumb can easily wheel it around. When shooting manual, it's much faster to use the cameras with two wheels (instant control of more features without holding buttons.) Also, mid-level and higher bodies have a top-lcd screen which gives instant access and readout of more information.

So while they're not the same as the Xti and there's a bit of a learning curve to get used to the new layout, once you do pick it up, you realize you can do things more quickly than you can on a Rebel.

The D7000's body is made with a combination of polycarbonate and magnesium alloy. This gives it a heavier feel than the lower end Nikons (the D3100 & D5100 bodies are pretty compact.) When you get above the D7000 then Nikons bodies are pretty much full magnesium alloy (a little heavier than D7k). On Canon, the 60D is polycarbonate and the next camera up... the 7D is pretty much completely magnesium alloy.

The magnesium alloy is sturdier -- although I've never heard of a polycarbonate body breaking unless it was _seriously_ hit. Some photographers do prefer the "heavier" bodies.

I find that there seems to be a tendency along gender lines... women seem to prefer the smaller bodies which more comfortably fit their hands and also prefer the lighter weight. Men seem to feel that the small bodies are a bit scrunched and the larger bodies have a more comfortable fit.

Mirrorless cameras are smaller and lighter still. The m4/3 format uses a sensor which is considerably smaller than an APS-C sensor. In photography, larger sensors collect more photons, work better in situations with less light and have lower noise without having to manipulate the noise in software (de-noising has the undesirable side-effect of softening the image.) The sensor sizes for mirrorless cameras vary considerably.

Several high-end "pro" DSLR bodies offer "full frame" sensors. These are sensors which measure 24mm x 36mm -- the same size as a frame of 35mm film. Those sensors are expensive. To make the cameras more within the reach of consumers, camera makers offer DSLRs with "APS-C" size sensors. The overwhelming majority of DSLRs use APS-C size (e.g. your Rebel XTi, the Nikon D7000, etc. ... all APS-C.) That sensor is about 1/3 smaller than a full-frame camera.

Having a larger sensor also helps with image quality, allows you to create more background blur if you want it, etc.

While most mirrorless cameras have small-ish sensors, there are two notable exceptions: Sony's NEX series cameras use APS-C size sensors and Canon recently announced the new Canon EOS M, which also uses an APS-C sensor. So these are smaller, lighter cameras but they have the same sensor you'd find on a DSLR. Canon's EOS M has it's own line of lenses being introduced but ALSO is compatible with Canon's full line of EF & EF-S lenses which are used on their DSLR bodies (so it's quite a selection of high-quality glass.) If I were to buy a mirrorless camera, a priority would be a large sensor (such as the Sony NEX or EOS M.) BTW, I think the new EOS M doesn't start shipping until December (it's announced and you can read all about it, but I don't think any of us mere mortals can get our hands on one yet.)

As for lenses... in generally, the more expensive they are, the better they are (and there's a REASON they are more expensive.) Optical engineering is complicated. There are all kinds of ways to take shortcuts to reduce the cost of the lens... but unfortunately we're talking about laws of physics. When you take those shortcuts, there are always trade-offs. If you do not want to sacrifice in quality, then be prepared to shell out for your lenses. If you want a bargain price, then don't expect your images to compete with those taken by phenomenal glass.

There are too many qualities of lenses for anyone to be able to say "this one is better".

Lenses are objectively rated for contrast & resolution (the ability of the lens to resolve fine detail) and the measure it done at different distances from the central axis of the lens (which is generally regarded as it's "sweet spot" where it will yield the sharpest detail) and they degrade toward the edges. This is plotted onto a graph called an "MTF curve" (modulation transfer function). But MTF curves alone aren't the only quality you should consider and you can get yourself into serious trouble if you don't realize that the MTF curve is always plotted with the lens at "wide open" and most lenses do their best worked stopped down 1 or two stops. So it wouldn't really be fair to compare a 50mm f/1.4 lens to variable focal ratio standard zoom 18-55mm f/3.5-5.6 lens at the 55mm end BECAUSE the 50mm f/1.4 lens (clearly the superior lens) will probably not SCORE as well when you look at the MTF graph due to the differences of comparing a lens at f/1.4 to a lens at f/5.6 (if the f/5.6 lens doesn't get a better MTF curve than the f/1.4 lens then that f/5.6 lens is probably a real piece of garbage.)

One of the reasons for going with Nikon or Canon is because these two companies have the largest selection of lenses (at both entry levels and pro-level glass), have the largest numbers of photographers using their gear, and have the largest number of 3rd party makers who make lenses which also work with them.

You touched on but did not bring up focusing systems. If you're into birding, you may want a fast & accurate focusing system. The Rebel bodies all have 9 auto-focus points. The center point is a fast & accurate "cross-type" point. The rest in a diamond shape pattern but are one-axis only focus points. The 60D has the same pattern of 9 points, but ALL points are "cross type". When Canon introduced the latest Rebel body... the T4i, they gave it the 60D's focus system. So the T4i has 9 "cross type" points rather than just the single cross-type point in the center and 8 more non cross-type points.

The 7D has 19 AF points and ALL 19 of them are "cross type". The D7000 has 39 AF points, but only 9 of them are "cross type". The 7D has a number of features specifically optimized for fast shooting. It has _dual_ DIGIC IV processors (most cameras just have one processor.) It has a continuous burst speed of 8 frames per second (that's without locking the mirror up so you actually see the subject through the viewfinder between each frame rather than having the viewfinder go black while the camera rattles off the shots.) Only the high end pro bodies are faster. The 7D also uses CF cards rather than SD memory cards because CF cards have always had a faster transfer speed.

You may also want to research something called "digi-scoping". Theses are guys who are basically buying telescopes and then mounting the camera to the scope in order to do birding with extreme detail.

Posted on Oct 13, 2012, 9:49:42 AM PDT
K. Ballweg says:
Any camera you buy right now will take a period of getting used to, and as long as you shoot regularly, will become a matter of muscle memory within weeks. Ergonomics is another issue. You'll know if a camera feels right for your hand size pretty much when you pick it up and use it for a series of shots. Any of the new crop of entry level full frame bodies (Canon, Nikon, Sony) can take better shots than anything you've used to date, and, no matter which one you choose, there will be plenty of arguments for buyer's remorse for any system. So pick, and never look back.

Should you buy into DxOMark ratings? NO! Use it as one small element. Better by far to spend a day reading Roger Cicala's blog at http://www.lensrentals.com/blog. And also seriously consider narrowing down to a couple of bodies then renting a body/lens combo for your trip to have a better sense of living with the thing, rather than holding your nose and jumping in.

For the range of needs you've described you are going to be happier (my opinion) with one of the new full frame "entry level" DSLR, but may find that price, frame rate and weight put you into the Canon 7D, Nikon D7000 crop bodies as really good choices that will do what you need and leave budget for glass.

My suggestion is to look at glass first rather than body specs. Look at prices and ratings for a good walk around lens (20-100mm range roughly) and a long reach telephoto 300mm to 400mm in as fast as you can afford for birding. Look for image stabilization (a real argument for Sony's body based stabilization) and f/2.8 as most useful requirements you describe.

I started with a Canon rebel and got too deep into Canon glass to have any interest in changing now. Am very happy with my 5Dmk3, but if I was starting fresh I would lean more to Nikon then Sony right now based on sensor technology. Glass choices lead to endless arguments, but fact is the more money spent on glass regardless of brand, the happier you will be with the end photos.

Posted on Oct 13, 2012, 11:47:42 AM PDT
EdM says:
I suggest that the OP look at Canon and Nikon APSc DSLR bodies first. I suggest AGAINST a full frame body, like the forthcoming Canon 6D or the Nikon D600 for one simple reason. With a desire for bird shooting and distant wildlife, the crop factor of APSc will provide an important bonus for telephoto shooting - more effective reach.

One thing that DSLRs all have is the ability to autofocus quickly due to the phase detect autofocus mechanism. P/S cameras, by and large, have slower contrast detect system, thus the digital wait that the OP lamented about. Things are a bit better with modern technology, especially as a few models have hybrid phase/contrast detect AF sensors, but those hybrid models are not as good as plain phase detect AF, normally found in all DSLRs. When you shoot in Live View mode, you are normally using the slower contrast detect AF, even on a DSLR. See this for more info:

http://www.youtube.com/watch?v=VG6yhI5I8Qc

"Canon EOS 650 Hybrid AF vs. phase detection AF - by dpreview.com"

I believe that DxOMark ratings are but one factor to be considered, not the main thing. Typically, Canon offerings tend to do worse in those tests than do the ratings of Sony, Nikon, Pentax and a few more. It is not clear to what extent these ratings actually show the whole truth on sensors. There is a reasonable argument that Canon sensors can and do make excellent images, regardless of those ratings.

As I use Nikon gear which tests out better via DxOMark, I can place more weight on the results and feel good. I do have older Nikon DSLRs from when sensors were not as good, and IMO what DxOMark rates or shows is indeed true - that the latest generation of DSLR sensors really is better, especially for low light, high ISO shooting. High ISO shooting may matter more for distance shooting, especially in lower light conditions around sunrise and sunset when some animals become more active. I would certainly prefer the latest Canon T4i, e.g., over an older T1i that is available for lower cost, as the latest sensors [and other DSLR technology] from Canon are better than that found in earlier models. Likewise for the latest Nikon D3200, if one were looking for an entry level Nikon DSLR.

I would also point out that the best professional images are more likely shot at low ISO under good conditions, for better dynamic range, color, etc., and in these conditions, high ISO performance is not especially significant. However, when you need "every last drop" of low light, high ISO performance, I'd certainly give some benefit to what DxO says. So, I'd say that DxO does mean something, but it would not be a primary factor in deciding on a specific camera or brand.

For birding in particular, digiscoping is one possibility, but it is pretty specialized for that one task, and often uses a P/S with a telescope [and a tripod] for high magnification. However, in those conditions, you end up needing good light levels and must deal with normally slow focusing of P/S cameras. So, you may have to shoot many shots before the bird remains still enough to get a sharp, un-blurry photo. Beyond being not blurry from movement, you want the bird facing the camera so the bird's eye shows up well in the photo. With an APSc DSLR and a telephoto lens, e.g., 300 mm prime lens, you may need to get a bit closer that with digiscoping, but focusing will normally be quick and the ability to quickly take a shot will help get a good shot/pose by the bird. On Canon, a 300mm lens is like a 480 mm lens in FF 35mm terms. Likewise for a zoom lens that goes to 400mm, like the Canon EF 100-400mm f4.5-5.6L IS USM Telephoto Zoom Lens for Canon SLR Cameras.

See:

http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

nb- the "CROP FACTOR & FOCAL LENGTH MULTIPLIER" section is relatively more important to your issue, and some of this info is quite technical.

Plus, when you shoot a DSLR, the same camera serves quite well in normal shooting, while digiscoping is really more of a one trick pony - you would not use such an outfit to shoot wide angle landscapes or for normal portraits, e.g.

Note that when you want to shoot longer distances, the size, weight and cost of the lens always goes up on a relative basis.

Also, since you have been using Canon some, it is logical that a Canon feels more intuitive. As I have been using Nikon for decades, I am used to Nikon and it feels more intuitive to me. Still, in some of my photography classes, I have tried out and used Canon DSLRs owned by other students, like 50D, 7D and 1D III, and they seem fine also, even if I am not as familiar with details of operation. You can get used to whatever control system, but you may prefer a particular size like a smaller body [normally entry level] or perhaps a somewhat larger mid-size body, regardless of controls. This is a personal thing, and also relates to the size of your hands and fingers, as well as your eyesight relative to the view through the viewfinder. So, look through various viewfinders when you handle DSLRs as well.

All such decisions are compromises based on many variables, not least of which is your budget. Good Luck.

In reply to an earlier post on Oct 13, 2012, 12:03:49 PM PDT
"""
One big frustration I had with the C-5050 was the delay in the live view between shots. I remember having some great opportunities diving with manta rays and taking a shot, then the manta was gone by the time I could take the next one. Not only that, the delay between depressing the button and the lag between the shutter, often times caused the moment to be lost.
"""

If the flash was firing for those shots, you would have been affected by flash recharge time -- and built-in flashes tend to take more time to recharge than their low output would seem to need; most likely to avoid stressing the camera with high current loads.

And any camera using contrast detection focus will be slower than those using phase detection focus (though some decade old SLRs may be about as slow a modern P&S). On an SLR, focusing speed is also affected by the lens being used; some lenses have faster focusing motors [some Nikon lenses don't even have focus motors and only autofocus with bodies that have built-in motors].

"""
My in-laws had the 5dMkII, and I loved shooting with this camera. However, the lens was not satisfactory for reaching some of the wildlife, especially birds, and I used it briefly, while we were in the car, so I am not sure on the portability, layout, and menus.
"""

Something you'll have to get used to... Lenses are going to be BIG and expensive.

Just doubling the sensor size (diagonal) will result in a lens having eight times the volume (twice the width, twice the height, and twice the length) to produce the same field of view -- and in dim forest conditions, you'll want the fastest lens you can find... f2.8 (no variable f3.5-5.6 zooms here). Most P&S have sensors small enough to have a 5x equivalency when compared to a full frame SLR... That means a P&S with a 100mm lens would have to have a 500mm lens on the full frame (125 times the volume!). APS-C SLRs are 1.5-1.6X equivalence (a 333mm would be the equivalent of the full frame 500mm)

As for ergonomics -- that's partly personal... I, for one, can't stand the Canon EOS Rebel bodies; they are too small and cramped, with curves and edges that just don't fit my fingers (which aren't all that long). The EOS x0D series, OTOH, I find quite comfortable (I just wish Canon hadn't changed the assignments of the three direct access function buttons on top -- gets confusing going from my 20D to my 50D -- oh, that's another difference between the Rebel and x0D; the Rebels require going into the main menu for more operations, and don't have a top status LCD panel; one can learn how to make most adjustments on an x0D without having to really pull it away from one's eye). Nikon's have a third shape/fit -- so you may want to try holding samples of each, with lenses of the size needed mounted so you can test the balance.

In reply to an earlier post on Oct 13, 2012, 1:35:15 PM PDT
Last edited by the author on Oct 13, 2012, 1:42:21 PM PDT
®ichard says:
I am a photo nerd so I play with many cameras (but I don't bust out the calculator, formula or ruler when I photograph, I don't want to be a technical shooter like Ken Rockwell, just know the fundamentals). It wouldn't take too long for me to get use to a Canon or Sony layout. Back in the $300 slr days we had to buy a camera for school. Most of the girls picked the lightweight canon or Minolta, I just picked the more heavier built nikon. Basically I just picked a camera since I knew nothing about camera back then and probably was generalizing from first impression.

Since your budget is pretty liberal at 3.5k I would pick a full frame (FX) and get one good lens. If you planning on going out for another safari in your case or like to shoot bird then the reach of the aps-c (DX) will be more useful (take any lens and time it 1.5x for nikon and everybody else, 1.6x for canon since their aps-c is a tad smaller so hence the tad higher ratio). I say Nikon D600 24.3 MP CMOS FX) has 5fps and same AF system, layout as the Nikon D7000. Don't think the Canon 6d is out, they just announced it early so people don't jump ship or get mad why they don't have this or that. Release dates could be pushed on vaporware product (tom's hardware guide term for product base on spec/rumor). Don't buy DX lenses, they maybe cheaper, but they have more vignetting so you use lens profile correction. Nikon Capture/View NX applies this automatic as you view, for lightroom you have to go turn it on per image (maybe there is an auto, this option applies to all camera manufacturers too). That is because the diameter of the glass for dx is so small that it barely cover the sensor. Also noticed this on my sony nex 28mm pancake lens. The diameter of the glass is like 1/5 of the size of the nex aps-c sensor, you would think lens profile correction is at work here too. Otherwise I like the D7000 as I do lowlight events/ situation. sports, portrait, architecture building. Lowlighting (not taking about lens factor) would be ISO driven. Sport is ISO drive and processor power on the camera. Landscape you would look at the dynamic range of the sensor, portrait I would look at the color range of the camera. Most photography situation the bigger sensor is better, so go full frame if you can. Every accessories are more expensive too. As for the sport aps-c cameras the canon 7d and nikon d300s are aging models and are both due for an upgrade. But most people don't care to spend more on a processor or AF-system so they are on the back burner. I would be hesitant to buy one with a new model lurking probably next year, unless I need too. Camera cycle are 2-3 years (non entry -level), so you are stuck with a 3 year old tech.

for testing score, DXO mark test the sensor only, not the processing. Some people have concern (usually canon user) but it is one of the many data out there. It does have an industrial standard for its methodology rather then some guy eyeballing results on this personal test site and some crude non-standard measuring equipment. The thing is computer stats are what the computer see, human eyes are more bias and might prefer certain aspect over another. So you might not want to see all the dynamic range in the detail and or all the color range of the skin. Higher contrast and saturation kills those data, and people prefer that look. I don't live in a neon yellow world, but we do like see that over a natural pale yellow shirt I washed many time. That is why some people think DxoMark score are flawed, plus the method is not open knowledge, as sensor designers can always cheat when they know what to program for. (video game drivers will cheap on bench score as comcast download speed is base on original speed burst, not as constant as fiber optic and I have cable). Another thing is raw is just the data, as you process you just tossed all those data differential out the window on what is more natural. Add more saturation in LR those range of red will be less and mushed into lesser tone of red. Add more contrast the dynamic range disappear. Outside of native ISO, most of the extreme iso is how fast your processor can process. The camera processor does a lot of thing too, it is like using lightroom on the fly with programmed filter. So the one thing here that a good processor can do over post processing is the FPS of a camera. If you need FPS then you get the sport camera with the faster processor. Other things just post process your image to reduce noise or add saturation or whatever you like. But no site really test how fast the processor or what other stuff it can do on a camera. Sony sensor on Nikon do usually score higher in ISO and dynamic range in comparable models over canon. To compare site, dpreview also usually score nikon raw a little higher in the conclusion charts, the bar is longer (they just don't give a numeric score like dxomark, the overall dxomark score somehow is a compile of the 4 categorical scores, better to look at those categorical individually and they are closer then the overall score). Comparing to site big site the data is about the same. They also upload raw sample. They use Adobe aCR, which isn't the sharpest tool for nikon, but I not complaining as much I used too.

For M/3 or sony nex, the major advantage they have is the size. You don't need big lens on them either, so it is good for hiking.

Posted on Oct 14, 2012, 12:41:58 PM PDT
Last edited by the author on Dec 18, 2012, 3:47:08 PM PST
Michael C says:
If it is within your budget you might want to consider a used/refurbished Canon 1D mkIV for the advantages it offers for birding. It appears to be the last Canon body that will allow AF to function when a lens plus extender combination with a maximum aperture of f/8 is used. All of the newer bodies turn off AF above f/5.6. Of course the 1D mkIV has an APS-H sensor with a conversion factor of 1.3X so that gives a little more reach as well. Daylight use of a high quality extender such as the Canon 1.4X III or 2.0X III ($480) and wide aperture telephoto lenses such as the EF 300mm F/4L ($1,500), for example, is much more affordable than the 600mm f/4 Canon lens ($10,000). You give up the aperture and not much image quality for 1/5 the price. There are more potentially usable combinations at f/8 than f/5.6 with a 2X extender. I would only recommend using high quality extenders such as the Canon II or III versions with top quality lenses. Any flaws the lens has will be magnified by the extender.

As others have mentioned, the controls on the higher end Canon bodies that you use while shooting are all reachable by the right thumb and forefinger (unless you've reassigned the DOF button, but it is near your left thumb while holding the lens barrel in your left hand). If there is a left-handed button you use frequently while shooting, you can always reassign it to the "SET" button that has no default function when you are actually shooting and not inside a menu. The "SET" button is located in the middle of the wheel on the back that is easily reached by your right thumb. My first digital body was a Rebel XTi. I used it for about a year and a half before buying a 50D. In terms of ergonomics and handling, the change was like walking out of a dark cave and into the light. The faster handling allowed me to get shots with the 50D I would have missed while adjusting settings with the XTi. Even though the 50D is now a spare body for a 7D, I can't imagine shooting anywhere now, other than a controlled studio, without a thumb wheel. For me, having the thumb wheel is just that much faster.

What can be debated regarding DxO mark is an entire forum's worth of material and opinions. Here is the basic flaw with DxO. They use their own third party algorithms to convert the RAW files instead of Canon's and Nikon's. Even then, the same algorithm doesn't work with both. So what DxO scores (that appear to say Nikon is 20% better picture quality than Canon) are really saying is that DxO wrote an algorithm for Nikon RAW files that it 20% better than the algorithm they wrote for Canon RAW files (Nikon is a major customer of DxO and it appears Canon isn't - Imagine that)! And based on the following from DxO Labs own marketing hype, Nikon appears to be designing their algorithms with the objective of performing well on DxO. Kind of like the 4th grade teacher who gives her students the exact information they will need to answer the known questions on a standardized test instead of teaching them a broad mastery of a subject. "DxO Analyzer is now used in the digital camera and component industry worldwide by such manufacturers as Nikon, Olympus, Panasonic and Samsung, to name just a few." (quoted from: http://www.dxomark.com/index.php/About/What-is-DxOMark2/Test-result-reliability) Notice what major imaging products company name is conspicuously absent?

No one can display a RAW file except as a binary string of zeroes and ones. To create anything intelligible it has to be at least partially converted first. Even within the set of sensors that use a 2X2 Bayer filter, the arrangement of the pixels varies from RGBG to RGBE to RGBi. Foveon sensors have one Red, one Green, and one Blue pixel in each location that doesn't even need to be demosaiced, but the data does need to be adjusted for the differences in signal response at different wavelengths and intensities. And then there are the hexagonal pattern sensors. Since sensors are designed differently from each other, and the analog to digital conversion is done using proprietary methods and often encrypted as well, comparing the binary output of different sensors is meaningless. I am aware that DxO claims they perform measurement BEFORE demosaicing. What this means is, according to their claim, they are only measuring the analog signal response of the sensor's pixels to a given amount of a specific color (wavelength) of light. What they are really doing is taking the post calibrated binary data and applying their assumptions to guess at what the calibration level was (for each intensity and wavelength) and backtracking to what they think the analog signal response was IF they guessed right in their assumptions. While this is all fine and good, even if they can accurately measure the analog signal response, NONE of the sensors can produce an intelligible image until calibration of that signal response in the form of analog-to-digital encoding and then application of an algorithm to account for the different signal response to different intensity of light at different wavelengths. What would be much more meaningful and revealing of the relative accuracy of dissimilarly designed sensors would be to measure how consistent each design is to provide the same result in a color space such as sRGB AFTER calibration has been applied to the signal response since none of us can use the RAW data until it has been converted to a bitmap raster array format.

Update: Canon recently announced a firmware update for the 5DIII scheduled to be released in early 2013 will allow AF to function with lenses and lens/extender combos with a maximum aperture up to f/8. They've already released a similar firmware update for the 1D X.

In reply to an earlier post on Oct 15, 2012, 3:18:45 PM PDT
- Ignore DxOMark. In a nutshell, DxOMark only looks at individual pixels. Which is something like judging the quality of a diamond ring using ONLY an electron microscope to view it.

- While I think m4/3 is a very good light and portable system for producing high quality images, it still can't compete with DSLRs for challenging subjects like sports, low light and birding. Great choice for a vacation camera, though, when you really don't want to lug around a heavy camera and lens slection with you everywhere.

- Birding lens selection for Sony and Pentax appears to be extremely limited if you ignore third-party lenses like Sigma and old, used (and possibly manual) film-era lenses.

In reply to an earlier post on Oct 16, 2012, 9:22:10 AM PDT
R, you say that DxO has an industrial methodology, could you explain that methodology to me? DxO does not publish their testing methods, and will not explain their method. It may be that they do apply good scientific rigor to their tests, but, as they do not explain the methodology, we can not reproduce their results.

ok, you do mention that their method is not open knowlege, but, I think the point deserves emphasis. Also, one of the things they do explain is that their method, whatever is it, attempts to score only the sensor. I am unable to use only the sensor, and whatever they do to try to only score they sensor, is not reflected in the photos.

Dpreview has a great side by side comparison tool. Same image taken under the same conditions, many different cameras. I can't see the difference indicated by the DxO scores. I can see some difference, and often yes, the camera with the higher DxO score produces a better image, but even a wide difference in score may not be reflected in test images.

I think that if the controls feel natural in your hand, and the camera is comfortable, in general, same price point will yield similar results regardless of brand. A $1200 canon will produce a similar result to a $1200 nikon.

Michael C reccomends the 1Dmk4. I shoot sports with that camera, and I know people who shoot birds with it. It will produce great results for you. The controls are well laid out. I was able to transition from the rebel xt to the mk4, and it made sense, although there is a learning curve. It is heavy. Use a black rapid sling instead of a conventional neck strap to reduce the neck strain of carrying the beast.

In reply to an earlier post on Oct 16, 2012, 11:08:34 AM PDT
®ichard says:
I read your comments and sorry for your concerns. I'll reply "if" I fell like it later.

in the meantime fell free check out dxomark forum:
http://forum.dxomark.com/

In reply to an earlier post on Oct 17, 2012, 10:40:04 AM PDT
EdM says:
Paul - You are incorrect on DxOMark and "methodology". Further, whether ® [and why don't you know/use one of the methodologies (cut/paste, e.g., if not a character viewer) for inserting the known character ®, unless you intend to insult or denigrate?] can explain something to you depends on YOU in the first place.

A nuclear physicist might well describe the latest theories and math/calculus in developing the GUT, Grand Unification Theory, but that doesn't mean that you or I would be able to understand what they do. Likewise with the physical processes of DxO and how this reflects the microstructure and electronic transformations to result in a digital output from a sensor from a given light photon input to that sensor. More on this below.

You have also misused the term:

http://www.techdarkside.com/process-or-methodology

"Methodology: a body of methods , rules, and postulates employed by a discipline : a particular procedure or set of procedures.

"Process: a series of actions or operations conducing to an end; especially : a continuous operation or treatment especially in manufacture."

Even describing a process does not imply giving up the "secret sauce" or specific algorithms actually used. Still, the methodology has been well described seriously on the excellent Luminous Landscape, by a physicist who is expert in the relevant area. The trick is that you and many others do not like the results, and thus attack the source of those results as invalid, e.g. It would seem that you welcome the concept of killing the messenger... Back to DxO:

http://www.luminous-landscape.com/essays/dxomark_sensor_for_benchmarking_cameras.shtml

"Figure 1a already shows quite some interesting information:
"As a general rule, larger sensors outperform smaller ones....
...but newer models generally outperform older models. In particular, the newest APS-C models (Nikon's D7000 and Pentax' K-5 and Sony Alpha 580) outperform the older 1.3× sensors and even most full-frame (1.0×) sensors due to a significantly lower noise floor...

"Surprisingly, except for the 1/1.7" segment, none of the Canon models are currently best-in-class[6] compared to their competition. This is partly because Canon's two full-frame models (5D Mark II and 1Ds Mark III) are currently 2 and 3 years old...

"As we are digressing here anyway, Figure 2 shows that Nikon (gray labels) originally lagged behind Canon (white labels) in terms of the image quality of its D-SLR sensors[7]. But with the introduction of the Nikon D3 in mid 2007, Nikon[8] appears to have overtaken Canon in DSLR image quality - at least for now..."

"So How Fair is the DxOMark Sensor Score?
"There is no simple objective answer to this important question. Probably every image quality expert would have a somewhat different personal preference for a benchmark like this. But my impression is that the benchmark is pretty useful: I analyzed the model and the data, but didn't find any serious flaws...

"Complexity
"Undoubtedly complexity is a fact-of-life when you design sensors. And to DxOMark's credit, they allow you use just a single figure score to compare camera body image quality...

"Undocumented formula
"Documentation about the way the final DxOMark Sensor score is computed from Dynamic Range, Color Sensitivity and Low-light ISO scores is not currently available...

"Metric measureable per ISO setting?
"It might have been clearer to have a single "perceived image quality" metric that could be measured at different ISO levels. This is particularly relevant because some cameras excel in high ISO conditions (requires a low noise floor) while others excel in low ISO conditions (requires large sensor)..."

"About Peter van den Hamer
"Peter van den Hamer is a physicist by training who has been working in the electronics industry in the Netherlands for over 20 years. Apart from his photography (currently on display at a Dutch art gallery) he occasionally writes about technical aspects of photography on his website..."

The author states that he uses a Canon 5D II, so his viewpoint can not reasonably be viewed as biased against Canon. As Canon sells more cameras than any other camera company and makes its own sensors, it may be that Canon has hit some internal technical roadblock in its fab facility, or that Canon does not believe these results are material to its bottom line or the performance of its cameras as used by most people.

It may be that Canon devotes more time and technology to good jpeg performance, as that is used by the vast majority of people who are not camera/photography geeks. My position is that I didn't doubt that Canon was ahead of Nikon in sensors in the early-mid 2000 decade, nor do I doubt that Nikon is ahead at this time. Still, competition is good for the consumer, and I expect that Canon will improve in the future. In any event, the technology is improving in general ["newer models generally outperform older models"] which is good for everyone.

In reply to an earlier post on Oct 18, 2012, 9:51:05 AM PDT
If I read a peer reviewed scientific study, it does in fact give up the secret sauce. Industry standard testing organizations, IEEE and UL for example, provide great detail on their testing standards. An article on a third party website that extracts meaning from the text on the DxO website, as much as possible. It's a good document, but it doesn't provide the complete testing methodology. It also doesn't provide the explaination behind DxO's claim to account for any pre-cooking of RAW data, unless I missed that in my quick read.

The part about Fixed Pattern Noise is interesting. That might seem to account for a portion of the score imbalance, as canon seems plagued with that problem, and Nikon corrects it away. As the article points it, photoshop (or whichever software you prefer) can remove that noise very effectively, resuting in final images that don't show the difference DxO scores would indicate, if processed correctly. In the Nikon raw image, that noise has been handled in camera, in the Canon raw, there's a bit more work to be done.

As I said, it is a good article, and explains many of the terms relevant to the testing and the scores. very useful, and I will hold onto that link to help answer questions, my own and other people's.

I agree that Canon held the lead some time ago, and Nikon has it now. I don't think it was or is as pronouced as DxO makes it appear, and I think that has to do with their attempt to measure the sensor in isolation. My objection is when the DxO score is presented as authoritative, across brand and format, or when small differences are presented as if they are a big deal. I also object when people say a particular camera is overwhelmingly better based on 1 FPS, or one additional megapixel. You can post another wall of text to disagree, but you are quibbling over small details in cameras with similar performance for price. As you say, the competetion is good for everyone. Canon is not going out of business over the difference in DxO scores, and Nikon won't go out of business over some other temporary difference that comes along, just as they didn't go under in the past when Canon had some advantage. Some of the other brands may leave the camera segment, but even then, it's probably not over performance differences.

Posted on Dec 12, 2012, 4:31:49 PM PST
Everyone says Nikon, Canon or Sony, and while each compared to each other has certain appeals and preferences through their different models, when only referring to those 3 I would choose Nikon 9 times out of 10, but if you do have a decent amount of money to spend I suggest you invest in Leica cameras...check out their dSLR's, they blow others out of the water...just not as easy to get your hands on them as with the other brands.

In reply to an earlier post on Dec 18, 2012, 2:09:09 PM PST
Kyle Brady says:
The 6D seems like a great FF camera, but not ideal for OPs needs (birding). He'd benefit from the crop sensor and higher FPS / better AF of the 7D or 60D.

In reply to an earlier post on Dec 18, 2012, 3:46:09 PM PST
Michael C says:
With the high magnifications used for birding, I would recommend against the 60D since it does not have AF Micro Adjust. The longer the focal length and the wider the aperture the more critical this becomes.

Update to my previous comment on this thread: Canon recently announced a firmware update for the 5DIII scheduled to be released in early 2013 will allow AF to function with lenses and lens/extender combos with a maximum aperture up to f/8. They've already released a similar firmware update for the 1D X.

In reply to an earlier post on Dec 18, 2012, 5:13:58 PM PST
Since a firmware update can't change the angles of the focus point wedges, all this update can do is /allow/ the autofocus logic to run with a lens narrower than f5.6...

Both of my x0D Canon's already allow lenses past f5.6 (else my Tamron f3.6-6.3 wouldn't focus at all at long focal lengths). Focus is slow, and seeks in lower light.

So a firmware update to the listed models won't mean "good" focusing (in speed), just that the camera won't refuse to focus if the aperture is narrower than f5.6.

In reply to an earlier post on Dec 18, 2012, 7:57:14 PM PST
Michael C says:
You are correct that phase focus performance will be better, due to the wider angles of the light from the edges of the lens' objective, in a lens with a wider aperture compared to a narrower lens with the same focal length. But with long telephoto lenses even an f/4 or f/5.6 lens has a much wider objective than, say, a 50mm f/1.4. Focus performance will also be better for any given aperture the more light the system has to work with. In very bright sunlight there is more light striking the focus sensor array through an f/8 lens than would strike the focus array through an f/1.2 lens in near darkness. Just like the image sensor, the AF sensor must deal with a noise floor. The more light, the higher the signal to noise ratio, the more accurate the focus can be. All x0D bodies prior to the 60D are "rated" to focus with lenses that report an aperture of f/5.6 or wider, but will "hunt" and often still focus with narrower lenses in bright enough light. It is my understanding that in the newer bodies AF is completely switched off with lenses reporting a maximum aperture narrower than f/5.6 (or f/8 with the bodies that got a firmware update), and will not even "hunt" to attempt focus at narrower apertures. I do not own a 1D X, 5D mkIII, 6D, 60D or any of the T2i or newer Rebels to test this.

Just for experimental purposes I mounted a Kenko C-AF 2X Teleplus Pro 300 between my Ef 24-105mm f/4L IS and several bodies. Here is what I found.
5D mkII- Focus is noticeably slower than without the extender but will usually achieve lock whether the center focus point is selected or with auto select. When focus lock is achieved it is as accurate as without the extender attached.
7D- The camera will hunt but rarely find focus using the center point only. With auto point selection it will usually achieve focus lock using one of the wider points. When focus lock is achieved it is accurate.
50D- When the center point is manually selected I could not get it to focus at all. It would hunt, but not find focus. With auto point selection the results were similar to the 7D, but it was slower and found focus less frequently.

The f/5.6 limit seems to have been an arbitrary one set by Canon for the xD bodies newer than the 1D mkIV in an apparent attempt to discourage use of extenders as opposed to their super telephoto lenses. They soon heard from many of their premium customers that they were using extenders WITH the super telephoto lenses, not instead of them. If anyone is not happy with the AF performance at f/8, they can still set the lens to MF.

In reply to an earlier post on Dec 18, 2012, 9:45:19 PM PST
"""
You are correct that phase focus performance will be better, due to the wider angles of the light from the edges of the lens' objective, in a lens with a wider aperture compared to a narrower lens with the same focal length. But with long telephoto lenses even an f/4 or f/5.6 lens has a much wider objective than, say, a 50mm f/1.4.
"""

The physical diameter doesn't really apply... It is solely the angle of the "edge" rays hitting the phase detect prisms. The telephoto may by physically larger diameter at even f5.6 than the 50mm f1.4 -- but since the aperture is so much further from the sensors, the angle may still be much narrower.

Posted on Dec 19, 2012, 3:15:36 AM PST
Last edited by the author on Dec 19, 2012, 3:19:05 AM PST
Michael C says:
For similarly designed fixed focal length lenses you are correct about the light angles. For constant aperture zooms I'm not so sure because the diaphragm is fixed behind all the elements that move to change the focal length and the diaphragm's distance doesn't change in relation to the focus array/focal plane even as the focal length changes. Perhaps the rear elements in those lenses change the "effective" distance? After some reading on the subject since my last comment it turns out the angle, in and of itself, is not the critical factor in focus performance of auto focus arrays. The amount of light needed to produce a usable signal above the noise floor is usually the determining factor. Granted an f/1.4 lens will let more light through in the same conditions than an f/8 lens will. But that 5 stop difference is nowhere near as great as the difference (in terms of the amount of light) between EV 1 and EV 18.

In reality none of the modern systems are using "edge" rays from the edge of the light cone in the way manual focus screens and their prisms did. Several factors come into play, including lens edge distortion (blur), lens edge vignetting (amount of light), and secondary mirror size (it has to be small enough to fit on the primary mirror at a 90 degree angle without contacting the shutter/sensor assembly). But even with reduced base length, the limiting factor with current phase focus systems seems to be the electronic sensitivity of the line sensors on the other side of the microlenses that split the light in the floor of the light box. Specifically, it is the amount of light required to produce a usable signal that can be distinguished from noise (S/N ratio). My 50D can only focus in light down to EV 0.5, my 7D down to EV -0.5, and my 5DII also down to EV -0.5 (but the larger mirror box for the full frame camera allows a larger secondary mirror and thus a wider base length). The 1D X and 5DIII can focus down to EV -2.0. That is 1/4 the light the 5DII needs to be able to focus!

All of that to say this: If the focus system in the 1D X can work down to EV -2 with an f/2.8 lens, then at light levels well above EV 1 there is enough light reaching the sensor array to produce a usable signal when an f/8 lens is mounted. The "tape trick" some have used with non-OEM lens extenders in combinations that exceed f/8 to prevent the lens reporting its effective aperture to Canon bodies bear this out. Will it be as fast a wider lens? No. Will it be as accurate? No. Is it still useable? Many say yes. Canon intentionally disabled what many users consider still usable AF at f/8. It wasn't a very big deal to most of the 60D or even 7D users because most of them had never used a 1 series body that would AF with an f/8 extender/lens combo. When they did it to the 1D X and the 5DIII (which some former 1D mkIV and 1Ds mkIII users have chosen over the 1D X for the higher resolution) Canon heard the howls from some of their biggest spending customers in the only area where they're still clearly superior to Nikon (super telephoto lenses and frame rate - what sports and wildlife shooters look at), and they relented and enabled AF to stay active through f/8.

In reply to an earlier post on Dec 19, 2012, 3:28:19 AM PST
Last edited by the author on Dec 19, 2012, 3:30:04 AM PST
Michael C says:
"Both of my x0D Canon's already allow lenses past f5.6 (else my Tamron f3.6-6.3 wouldn't focus at all at long focal lengths). Focus is slow, and seeks in lower light."

I have read that some third party lenses "fool" the Canon bodies by falsely reporting their maximum aperture.

The following quote is about 1/3 down the page at: http://www.the-digital-picture.com/Photography-Tips/Canon-EOS-DSLR-Autofocus-Explained.aspx

"Note that these thresholds are not absolute - a lens with a narrower aperture than the threshold might still work, but at reduced effectiveness, accuracy, and speed. Thus, Canon limits the functionality to the rated aperture for a given AF sensor. However, some third party lenses (e.g. Tamron and Sigma zooms with a max aperture of f/6.3 at the long end) effectively trick the AF system into thinking there's an f/5.6 lens attached. Likewise, although not condoned by Canon, it is possible to use tape to block some of the contacts on a Canon 1.4x extender used with an f/5.6 lens, resulting in the camera attempting to autofocus with an f/8 lens on bodies which are limited to f/5.6. Sometimes, it even works... "

I've read accounts of the tape trick successfully being used on non-Canon extenders with both Canon and other lenses as well to use AF at f/8 and even f/11 in very bright light.

In reply to an earlier post on Dec 19, 2012, 10:13:33 AM PST
"""
For constant aperture zooms I'm not so sure because the diaphragm is fixed behind all the elements that move to change the focal length and the diaphragm's distance doesn't change in relation to the focus array/focal plane even as the focal length changes. Perhaps the rear elements in those lenses change the "effective" distance?
"""

I have an ancient 80-210 constant aperture zoom (would you believe "Focal" brand, from K-Mart) that fits my Canon A-1 (I did say ancient, didn't I?)...

It achieved constant aperture by having, at the 80mm end, the second lens element/group (about 1.5" diameter) immediately against the first element (about 2.5" diameter). The effect is as if the first element had a mask blocking the outside 1/4" rim. When zoomed to the 210mm position, the second group draws back into the barrel, such that the entire first element focuses the 2.5" diameter into the 1.5" second group.

In short, the front of the lens is "stopped" down to counteract the larger apparent aperture of the shorter focal length...

In reply to an earlier post on Dec 19, 2012, 10:16:36 AM PST
"""
However, some third party lenses (e.g. Tamron and Sigma zooms with a max aperture of f/6.3 at the long end) effectively trick the AF system into thinking there's an f/5.6 lens attached.
"""

Yet the aperture display on my 20D, with the Tamron at 200mm, shows the maximum aperture as f6.3 when zoomed... If the lens was sending back a false aperture of f5.6, wouldn't one expect the exposure system to report f5.6?

In reply to an earlier post on Dec 19, 2012, 1:46:36 PM PST
Last edited by the author on Dec 19, 2012, 1:59:16 PM PST
"Yet the aperture display on my 20D, with the Tamron at 200mm, shows the maximum aperture as f6.3 when zoomed... If the lens was sending back a false aperture of f5.6, wouldn't one expect the exposure system to report f5.6?"

Remember, the camera keeps the lens' aperture diaphragm fully open for auto-focus regardless of what aperture is dialed in. I suspect the trick with f/x-6.3 lenses is that the lens reports f/5.6 ("Yeah, f/5.6 - that's the ticket!") when the camera first asks the lens to open fully. When you fully press the shutter release button, however, the camera, which sees it has an aperture setting of f/6.3 dialed in, tells the lens to stop down to f/6.3 to which the lens replies, "OK, you got it!".

In reply to an earlier post on Dec 19, 2012, 4:16:48 PM PST
Michael C says:
"If the lens was sending back a false aperture of f5.6, wouldn't one expect the exposure system to report f5.6?"

Not necessarily. I've been trying to find an article I read recently. It discussed more than one metadata field regarding aperture in the communication between lens and camera. Apparently the one that turns AF on or off is not the same one that reports the selected aperture in the viewfinder. This may have been left over from the early development of the EOS system when there may have still been a provision to set aperture from the lens, rather than the body. The lens reports it is an f/5.6 lens before being stopped down, but also reports it is currently set at f/6.3. That is why the tape trick works.
There are others who suggest the real cut-off isn't for any lens slower than f/5.6 but rather a lens must be faster than f/8.
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Discussion in:  Photography forum
Participants:  13
Total posts:  28
Initial post:  Oct 13, 2012
Latest post:  Jan 19, 2013

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