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Customer Review

229 of 236 people found the following review helpful
5.0 out of 5 stars Sharp low light performer, August 3, 2011
By 
This review is from: Panasonic H-X025 Lumix G Micro 4/3 LEICA DG SUMMILUX 25mm f/1.4 Leica Aspherical Lens (Electronics)
Note that I also have the Panasonic 20mm and the Nokton 25mm so I'll mention some of their differences.

It's pretty exciting to get hold of the first f/1.4 lens for the Micro Four Thirds system. Thankfully, the Leica brand didn't add a whole lot more to the price tag, although I still think it's a bit pricey.

This lens is like the big brother of the 20mm. It's twice the weight at 200g, and almost twice the height. The construction quality is good, mainly plastic, except for the metal mount. It has a 46mm filter thread - yeah, I can use my 2-stop ND filter from my 20mm lens.

The focusing ring is nicely damp and turns smoothly.

It comes with a carrying pouch and a relatively large plastic rectangular lens hood. You know that 46mm lens hood people are using for the 20mm lens? I'm actually using that instead, very little light fall-off and it's much smaller.

Auto-focus is silent and quick. However, auto-focus during movie mode isn't that fast but it's not just this lens. Manual focus is focus-by-wire and it's a pleasure to focus with the responsive focus ring.

The sharpness varies at different apertures. At f/1.4, the corners are slightly blur, centre sharpness is still alright. f/2.8 is tack sharp at centre, with the subjects at corners nearly in focus. The lens is tack sharp at f/4. I use it often at f/1.4 and the images are perfectly alright, provided you don't pixel-peep.

The depth of field is wonderful. Bokeh is creamy. This lens has a shallower depth of field than the 20mm lens. Even if the subject is near to the background, it can still blur the background effectively (more than the 20mm lens). There's a 3D feel to the photos that are shot this way, together with the background blur is very pleasing. Shooting at f/1.4 during the day would require a ND filter (highly recommended).

At f/1.4, chromatic aberration is barely noticeable, vignetting is slight.

The minor downside is probably the minimum focus distance of 30cm, compared to the 20mm lens' 20cm or the Nokton's 17cm.

Shooting with this lens under low light conditions is, of course, a pleasure. I'm using this outdoors primarily. For indoor shots with intention of capturing interiors, for me, it's 35mm and wider. After using the lens, it made me realise that my preferred focal length is actually 24-35mm.

This lens is pricey. The image quality it delivers is great, thankfully. So it's still good value for money.

------------------------------------------------------------

- vs Panasonic LUMIX G 20mm f/1.7 Aspherical Pancake Lens for Micro 4/3 Mount -

Should you get this lens if you already have the 20mm lens?

f/1.4 vs f1/7 is about two thirds stop of a difference. That's minor difference but sometimes matters.

The 20mm is smaller and lighter. The 20mm is wider and more flexible in the sense that you can get the 25mm field of view by just cropping (unless you follow the code of thou-shall-not-crop).

Sure the 25mm lens is sharper, but you can't say that 20mm is far off. The main advantage, at least to me, is the 25mm lens' shallow depth of field, which is the main reason why I bought this.

------------------------------------------------------------

- vs Voigtlander 25mm f/0.95 Nokton Manual Focus Lens for Micro 4/3 Mount -

The Nokton lens is two times heavier, 410g vs 200g. It's also longer, 70mm vs 54.5mm. The build is excellent and looking through all that glass can be mesmerizing (intangible).

The Nokton is a manual focus lens which takes some time getting use to it. Auto-focus is more convenient I must say, seeing that I'm already spoiled by auto-focus.

The aperture ring on this big guy which means you can change your aperture while shooting videos. Manual focus is useful for shooting videos. Using manual focus is generally faster (for video) and you can always be sure you're focusing on the right subject - there's not going to be any auto-focus hunting. Big advantage if you require that change of depth of field from shallow to deep.

For bokeh, both are quite evenly matched.

The Nokton has a 1 stop advantage which can mean the difference of getting or not getting a shot during low light. However, shooting at f/0.95 comes at a cost of a slightly hazy image (some prefer to call it a glow).

I typically use the Nokton at f/1.4. Centre sharpness improves dramatically when stopped here. At deep focus, the corners aren't particularly sharp. This lens just isn't as good at corners. But for my purposes, which involves posting photos to the web, it's not a big issue. If you're printing, then, yes, you should check out more sample images.
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Tracked by 8 customers

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Showing 21-30 of 42 posts in this discussion
In reply to an earlier post on Feb 15, 2012 12:52:32 AM PST
Last edited by the author on Feb 15, 2012 1:21:43 AM PST
Eric,
Yes, the basic "exposure setting" will be the same at any given f/stop and ISO. But the image quality isn't; you have to turn the ISO down 2 stops on the micro 4/3 camera to achieve the same image quality.

I never said the LENS is 2 stops better, I said the larger SENSOR (or rather, the whole camera) has a two stop speed advantage. And one of the reasons is that a full size lens' circle of light covers 4x more area than a micro 4/3 lens does, delivering 4x the number of photos (light information) to the sensor at the SAME exposure. Therefore the lens does play a part in it.

This can be quantified as the amount of GAIN (signal amplification) that the system needs to output to deliver the same level of final image brightness.

On a micro 4/3 sensor, the signal gain (signal to noise ratio, and thus the image quality) at 100 ISO is the same as the signal gain at 400 ISO on a FF sensor.
400 ISO has the same signal to noise ratio as 1600 on FF, and 800 the same as 3200.

A sensor is a photon collector; a full frame sensor collects 4 times as many photons (signal) at the same exposure reading as a micro 4/3 sensor does, while the background noise remains constant.

4x the signal = 4x signal to noise ratio at any given ISO setting.
So to achieve the same image quality, you have to set the ISOs differently as described above, and stop the lens down 2 stops on the FF camera. Now both sensors are collecting the same number of photons which = same image quality, and not so coincidentally, the depth of field becomes the same too.

The following settings will give virtually identical results in terms of:
1. Field of view, 2. Depth of Field, 3. Motion Blur, and 4. Image Quality (Noise/Graininess)

Micro 4/3:
25mm lens, f/2, 1/60 second, ISO 100

Full Frame:
50mm lens, f/4, 1/60 second, ISO 400

You will notice that the aperture diameter (focal length divided by f-stop) is the same in both those scenarios: 12.5mm. That's one of the reasons they're equivalent. A full size 50mm f/2.8 lens is equivalent to a M4/3 25mm f/1.4 lens, once you equalize the ISOs to the same signal-to-noise ratio.

The lens isn't "faster", the whole camera is. Everyone already knows FF cameras deliver better low light performance at the same settings; they're faster. The whole system is about 2 stops faster overall, so you can just bump the ISO up by 2 stops and get the same results.

In the example above if you wanted to shoot faster, you could do it with the FF camera by keeping the ISO at 400 and setting the lens at f/2. Now you can shoot at 1/120 second--that's two stops faster with the same image quality. To achieve the same 1/120 second speed on the micro 4/3 camera and maintain the same image quality, you would have to set the f-stop to f/1.0. But you can't because the lens isn't that fast.

Get it?

In reply to an earlier post on Feb 15, 2012 1:43:56 AM PST
Edgar Matias says:
It's the debate that refuses to die... :-)

That's like saying a fat person is faster than a skinny person, because more of them crosses the finish line. They're not faster; they're just bigger.

While what you're saying is technically correct, the units of measure you're using are inappropriate for what's being described. I could tell you my weight in Gs, but why would I? Nobody would understand what I'm saying. Most people think in lbs -- not even kg, much less Gs.

What we're really talking about here is the real resolution of the image, normalizing for all other factors. That's more meaningful to a photographer than using a unit of measure for brightness.

In reply to an earlier post on Feb 15, 2012 2:14:49 AM PST
Last edited by the author on Feb 15, 2012 5:34:51 AM PST
Edgar,
I don't see how your analogy about fat people relates to camera sensors. The signal-to-noise relationship can be easily quantified with simple math to show what settings on a m4/3 system are equivalent to FF. Fat people and skinny people are all over the map when it comes to running ability. Is it a 100 yard dash or the mile? There is no real correlation.

Also I never use any "unit of measure for brightness" in my photography. You don't need to know anything about signal-to-noise ratio to understand the simple fact that a FF camera is 2 stops faster. I only discussed signal amplification to explain WHY a FF camera has a two stop advantage to those who still don't understand.

All the photographer needs to know with M4/3, is that to achieve identical results in terms of field of view, depth of field, and ability to stop action, she needs to use a lens with half the focal length, and open the lens up two stops.

Pretty simple. The only problem being it would take a 25mm f/0.7 lens to match the all-around performance of a 50mm /1.4 on FF. (A 25mm f/0.7 and a 50mm f/1.4 both have a max. aperture diameter of 35.4mm.)

In reply to an earlier post on Feb 15, 2012 6:00:28 AM PST
Edgar Matias says:
Hey David,

Your way of explaining things is why they don't let engineers design user interfaces... ;-)

Saying that a FF camera is 2 stops faster is backwards. It's lens-centric language, when what's really different is the sensors.

The FF sensor is DOUBLE the diagonal (4x the area) of a m43 sensor.

In other words, the m43 sensor is HALF the diagonal (1/4 the area) of a FF sensor.

Because the FF sensor is 4x the area of the m43 sensor, it has 4x the normalized megapixels. The m43 sensor has 1/4 the normalized megapixels. For example, if you take a 4 megapixel FF sensor image and crop it down to the size of a m43 sensor, you'd have a 1 megapixel image (1/4 the area of 4 megapixels = 1 megapixel).

Because the m43 sensor is half the diagonal of the FF sensor, it's like cropping a FF sensor image down to half its diagonal. You're cropping out the sides, top, and bottom of the image, so your angle of view is narrower. This means you need a wider lens to get back the FF angle of view that you cropped out -- a lens twice as wide. That's why 50mm on FF = 25mm on m43 (twice as wide).

You also need a faster lens on m43 to compensate for the extra depth field you gained when you cropped out the blurry bits of the bigger image. You need a lens that's 4x as fast or double the f-stop value. That's why a 50mm f/2.8 lens on FF has the same DOF as a 25mm f/1.4 on m43 (double the f-stop).

Because the m43 lens takes in 4x as much light (a 2 stop advantage, relative to sensor size), you can shoot the same picture in much lower light, but you lose 1/4 of the image size vs. FF at f/2.8.

All of the above assumes that the FF and m43 sensors are identical in all aspects other than size. Sensors are constantly improving, so one of today's m43 sensors is roughly equivalent in resolution to a FF sensor made 10 years ago.

That's a lot easier for a photographer to understand than what you wrote. :-)

In reply to an earlier post on Feb 15, 2012 1:17:14 PM PST
Last edited by the author on Feb 15, 2012 3:23:49 PM PST
Edgar,
You were going along pretty well until you said:

"Because the m43 lens takes in 4x as much light (a 2 stop advantage, relative to sensor size), you can shoot the same picture in much lower light, but you lose 1/4 of the image size vs. FF at f/2.8."

Quantity of light collected is measured in photons. A 25mm f/1.4 m4/3 lens does NOT "take in" 4x as much light as a 50mm f/2.8 FF lens. It has 4x the brightness-- but it's spreading it over only 1/4 the area.
Or you could say the 50mm/2.8 lens has 1/4 the brightness. But it spreads it over 4x the area. Therefore the amount of photons that are taken in and recorded at any given exposure, say 1/60 second, is the same.

An analogy for total light would be paint. For every one coat of "paint" that an f/2.8 lens paints the sensor with, an f/1.4 lens lays on 4 coats of "paint". But the FF f/2.8 lens is coating a surface 4x the area, so it's really just spreading the same quantity of "paint" over a larger area. The total paint (photons) delivered is the same. So those lenses are equivalent, in terms of photon gathering ability AND depth of field. As a result the two photos are indistinguishable, when you adjust the ISO to get the same shutter speed.

A 50mm f/2.8 FF lens "takes in" the same number of photons as a 25m f/1.4 m4/3 lens at any given shutter speed. That's lens-centric language.
OR you can acknowledge that the 25/1.4 has a two stop advantage by virtue of its brightness, but the 50/2.8 has a two stop advantage by virtue of its 4x bigger image circle. They cancel each other out. THAT is truly lens-centric language.

The 25/1.4 and 50/2.8 lenses are equivalent in their performance. But a 50mm f/1.4 lens takes in 4x the number of total photons as a 25mm f/1.4 m4/3 lens at 1/60 second. It has the same level of brightness, but it's delivering it to 4x the area, so it's gathering 4x the amount of light information. It has a two stop advantage overall.

A camera's overall light performance is determined by it's ability to gather light information (photons), not just by it's brightness. That's why tiny point-and-shoot cameras deliver terrible low light performance, even if they have a "fast" f/1.7 lens. It's not really "fast" in absolute terms compared to an f/2 SLR if it can't shoot in low light, is it?

In reply to an earlier post on Mar 6, 2012 8:45:53 AM PST
Last edited by the author on Mar 6, 2012 10:02:54 AM PST
peevee says:
David Siegfried wrote: "25mm f/1.4 at 1/60 second @ ISO 100 on m4/3

gives an equivalent image to:

50mm f/2.8 at 1/60 second @ ISO 400 on FF"

David, it seems you are counting the same thing twice. f/2.8 on FF (1x) will have the same aperture opening diameter as f/1.4 on m43 (2x), so the same exact amount of light comes through at the same time.
So it should be either
50mm f/1.4 at 1/60 second @ ISO 100 on FF
or
50mm f/2.8 at 1/60 second @ ISO 400 on FF

"A camera's overall light performance is determined by it's ability to gather light information (photons), not just by it's brightness. That's why tiny point-and-shoot cameras deliver terrible low light performance, even if they have a "fast" f/1.7 lens."

And that is determined (assuming the distance to the subject etc are equal) by the area of the front lens divided by that number after F squared, isn't it? P&S have tiny lenses. And if they had bigger lenses, too much light would hit the given area of the sensor making it hot and noisy, so manufacturers keep relative sizes of lens and sensor in a reasonable range.

In reply to an earlier post on Mar 6, 2012 10:07:57 AM PST
Last edited by the author on Mar 6, 2012 10:23:05 AM PST
What do you mean "counting the same thing twice"? That doesn't make any sense.

As you just said "(50mm) f/2.8 on FF (1x) will have the same aperture opening diameter as (25mm) f/1.4 on m43 (2x), so the same exact amount of light comes through at the same time (1/60 second)."

So
25mm f/1.4 at 1/60 second @ ISO 100 on m4/3
gives an equivalent image to:
50mm f/2.8 at 1/60 second @ ISO 400 on FF

In terms of field of view, depth of field, motion blur, and noise levels, the two images would be virtually indistinguishable.

That's what I already said. Go back and read through the entire thread. It's been explained now several times over, you're just making me repeat myself.

What you said:
50mm f/1.4 at 1/60 second @ ISO 100 on FF
or
50mm f/2.8 at 1/60 second @ ISO 400 on FF

Those are NOT equivalent. They have different depths of field, and different noise levels. Besides, we were discussing equivalency across DIFFERENT formats: M4/3 vs. FF.
The only equivalent settings on the SAME format, are the SAME settings.

In reply to an earlier post on Mar 6, 2012 10:31:15 AM PST
Last edited by the author on Mar 6, 2012 10:44:59 AM PST
"P&S have tiny lenses. And if they had bigger lenses, too much light would hit the given area of the sensor making it hot and noisy, so manufacturers keep relative sizes of lens and sensor in a reasonable range."

A P&S lens has to have a much shorter focal length by nature of its sensor size. It's not physically possible to make a super wide aperture on a little 8mm lens, which is the "normal" focal length for P&S cameras. Yes, the full well capacity of P&S cameras is limited, so they have less dynamic range and color depth capability than larger sensor cameras. But that has little to do with what we were discussing which is simply determining real "lens equivalence" between M4/3 and Full Frame cameras.

The point I was making is that the light-gathering abilities of small sensor cameras is very small, even if they are rated as having an f/1.7 lens, which would be considered a "fast" lens in the 35mm SLR world. But f/1.7 P&S cameras are not really "fast" at all. You can't just go by the f-stop rating, that's all I was saying. You have to consider the full light (photon)-gathering abilities.

A 50mm f/1.7 DSLR lens vs. an 8mm f/1.7 P&S lens: They both say f/1.7, but the DSLR lens is FAST and the P&S is SLOW. Get it?
So don't judge a lens by its f-number alone.

In reply to an earlier post on Mar 7, 2012 9:21:42 AM PST
Last edited by the author on Mar 7, 2012 9:25:14 AM PST
peevee says:
David Siegfried wrote: "What you said:
50mm f/1.4 at 1/60 second @ ISO 100 on FF
or
50mm f/2.8 at 1/60 second @ ISO 400 on FF

Those are NOT equivalent. They have different depths of field, and different noise levels. "

David, I am talking ONLY about signal-to-noise levels, not DOF etc. And in this regard, those two and m43 on f/1.4 ARE equivalent, given the same sensor quality (minor differences do exist due to different sensor cooling, but it is significant only on ridiculous exposures, and I am not talking about those either). And that is why. Amount of light a sensor gets DOES NOT depend on the size of the sensor (in case you have a lens or other object in front of it), as you seem to think. It depends only on aperture area and exposure time. Assuming exposure time is the same, only aperture area is left. The area is calculated by the formula area=PI*(f/2N)^2 (assuming it is round, which is pretty close to reality), where f is focal length, and N is f-number (those 1.4 and 2.8 in our discussion). The focal length on FF is twice that of m43, so at the same f-number the area is 4 times as large, giving 4 times more light, and 4 times better signal-to-noise. But if you close aperture from f/1.4 to f/2.8, the area will decrease 4 times (see formula), 3/4 of the light we got at f/1.4 (the same light which produces the extra blur in out-of-focus areas and the extra exposure for in-focus areas) will hit aperture diaphragm instead of the sensor. So the amount of light (signal) on the sensor will be the same as on m43 with f/1.4, giving us the same SNR.

That is why I am saying that by BOTH reducing aperture (4 times by area) AND exposure time (4 times again, by increasing ISO and decreasing exposure time accordingly to achieve the same exposure), you counting the same effect twice. Only one or another is enough to get the same result as on m43.

In reply to an earlier post on Mar 7, 2012 10:09:58 AM PST
Last edited by the author on Mar 7, 2012 10:38:30 AM PST
You are adding a lot of confusion. The whole POINT of "equivalency" is that the DOF, exposure time AND signal-to-noise ratio must ALL BE THE SAME. Otherwise you do NOT create two equivalent images.

"I am talking ONLY about signal-to-noise levels, not DOF etc. And in this regard, those two and m43 on f/1.4 ARE equivalent"

No, not even in that regard. 50mm f/1.4 at 1/60 second @ ISO 100 on FF has twice the signal of the other two because it has two stops more photon gathering ability, and is the one that is not equivalent.

"Amount of light a sensor gets DOES NOT depend on the size of the sensor"

Wrong, that is a common photography myth. See link below.
Sensor size IS one factor. Total photons collected is related to: the density of the light (f/x.x) times exposure time (seconds) x sensor area. A m4/3 sensor collects 1/4 as many photons as a FF sensor does at the same exposure reading.
OTHERWISE IF YOU WERE RIGHT THAT SENSOR SIZE DOESN'T MATTER, THEN A 2x2 MICRON SENSOR COMPOSED OF ONE PIXEL WOULD GATHER AS MUCH LIGHT INFORMATION AS A FF SENSOR AT THE SAME EXPOSURE. REALLY?!?!

"I am saying that by BOTH reducing aperture (4 times by area) AND exposure time (4 times again, by increasing ISO and decreasing exposure time accordingly to achieve the same exposure), you counting the same effect twice."

You are confused -- I NEVER reduced the exposure time!! It remained constant at 1/60 second. A 50mm f/2.8 FF delivers the same number of photons (signal) as the 25mm f/1.4 m4/3 . I am not counting anything twice. And most of what you are saying is just re-stating the same things I already said, and then coming to a different (wrong) conclusion.

25mm f/1.4 at 1/60 second @ ISO 100 on m4/3 ~ 50mm f/2.8 at 1/60 second @ ISO 400 on FF

Because as I already summarized, "A 25mm/1.4 m4/3 has a two stop advantage by virtue of its brightness, but a 50mm/2.8 FF has a two stop advantage by virtue of its 4x larger image circle." The two cancel each other out. They are EQUIVALENT. Exposure TIME remains the same, DOF is the same, SNR is the SAME. I'm not "counting anything twice".

It's all been explained numerous times and in numerous ways. PLEASE, just go back and read the ENTIRE thread. It's a waste of time to keep explaining what's already been established.

And if you're still not convinced, read this:

http://www.clarkvision.com/articles/does.pixel.size.matter/#The_f_ratio_Myth