If your shooting on a Crop Sensor camera, and you put an EF lens on it, you should multiply the mm shown on the lens by 1.6 ~ So if you put a Canon EF 50mm f1.4L on your crop sensor it will "behave" like you put on a 85mm lens. You will still get the some of the added benefits of the L lens (like the larger aperture, faster/quieter auto focus, etc..) but it does "crop" off some of what would be seen on a Full Frame camera.
If you think there might possibly be a new camera body in your bag that has a Full Sensor body (like the 5D Mk II) I would not spend the money on any EF-S glass....
Are the L lens only for Full Sensor bodies? No! Some will say it is like putting High Octane fuel in a cheap car and it is overkill. I look at my glass purchases with that thought of upgrades for the future.
answered on October 10, 2011
I have a T2i which I've been very happy with. I started with a 55-250 EF-S lens and ended up upgrading the lens to the 70-200 F4L IS lens. I find that I do notice a difference in color, contrast and sharpness. Whether or not the difference is worth the money is really hard to say. What I can say with certainty is that you will notice a big jump in quality with any of those lenses over the 18-55 kit lens. I'm sure you'll notice a difference going from say the 15-85 to the 24-70, but this difference probably won't be as dramatic as just getting away from the kit lens. You are the only one who can say whether the significant price jump is worth it.
One big difference in the lenses that you are comparing is the maximum aperture that the lens provides. The 24-70 will let in a bit more light than either of the other lenses that you are comparing - when fully zoomed the L lens will allow in 4 times the amount of light as either of the other lenses. (This is not a function of it being an L lens, just of the maximum aperture). This will allow you to potentially get better shots in low-light situations and will also allow you to better isolate your subject by blurring the background.
Here are some of the other things I'd consider:
1. The difference between 15 and 24 or 28 on the wide end is pretty significant on a crop sensor camera especially. You have to multiply the focal length by 1.6 to find the full-frame equivalent so 15 on your camera is equivalent to 24 on a 5d. The 24 from the 24-70 becomes equivalent to about 38. So with the 24-70 lens you don't have much wide angle ability.
2. If you ever upgrade to a full frame camera then the 24-70 will be the only lens out of the three that you can use on that camera. The EF-S lenses only work on a crop sensor.
3. The resale value of nicer lenses is really good on eBay or Craigslist.
4. That 24-70 lens weighs more than your camera. It might get tiring carrying/using that lens on a daily basis. In addition, it might feel odd balance-wise. I bought a battery grip on eBay it helps balance out my heavier lenses.
The 15-85 and 24-70 are available to rent at LensRentals.com and might be available locally to rent or borrow too.
The other thing I've done is go to pixel-peeper.com or Flickr and look at images from actual users of these lenses. A search on Flickr for something like "Canon 15-85 kids portrait" will probably help.
The last thing I'll say is that if you haven't tried a prime lens then you should really give the 50 1.8 a shot. It's the best $100 I've spent in a long time. Play around with it in aperture priority mode and get some nice close-ups of your kids' faces. Just make sure to get their eyes in focus. You'll be very happy with the results.
Thanks Brad. After reading your comments, I sold my 55-250 and my 28-135 IS USM. I got $160 for my 55 and loss $20 on the 28. I try taking picture of my kids with just the 18-55 (almost the same zoon length as the 24-70L) and it doesn't cut it. I never got the reach that I needed. I'll trade that little extra bit of quality for versitility and get the Canon 18-200. Budgetwise, $500 vs $1500 is hard to justify with only a slight different in quality. Beside, the quality from the 24-70L is not as good as the 70-200L which is what you got. Though, I'll take your advise and pick up the 50mm f1.8 for indoor use.
answered on September 30, 2011
For those of us using DSLRs for video - the L zoom lenses constant aperature is very useful when zooming (as anyone who has used a zoom lens without it will atest to ;) )
Absolutely! I only use L glass on my T2i. I will upgrade my body some day, but in the mean time....NO CONTEST. I love my 70-200 F2.8L IS. Best money I've ever spent. I need wide now though. I can't decide on 16-35mm or the 24-70mm. Decisions. I shoot mostly corporate videos so I think if I'm gonna go wide, go as wide as possible. IDK.
Dylan, i just bought the Sigma 17-50mm for a wide-standard zoom range on my 7D. It's wide enough on the 17mm without barrel distortion; i don't know if the 24mm will be on a cropped T2i though - give them a try.
The only issue with the Sigma, is the zoom ring is not as buttery smooth as the Canon 17-55mm which i looked at - but for my needs, saving the $300+ by getting the Sigma with the quality of lens the Sigma provides outweighed this need, but if you are doing lots of zooming while shooting, you might want to look at the 17-55mm Canon.
Sorry for the off topic post :)
[Deleted by the author on Jan 1, 2012 9:48:57 PM PST]