Which Lenses to Buy?

[andnowimbroke]

For some reason I thought the Tamron VC-version was a 17-55mm, and the non-VC was a 17-50mm. Did some reference checks and have no clue how that stuck in my brain. Either way, the Tamron VC would rank fourth in the three listed.

[JTPAIN]

Surely the Canon 15-85mm gives better IQ and functionality than the Canon 17-55mm and the Tamron 17-50mm anyway?

[thekingb]

Surely the Canon 15-85mm gives better IQ and functionality than the Canon 17-55mm and the Tamron 17-50mm anyway?

In its focal range, yes, the 15-85 is more "functional." But the Canon 17-55's IQ is considered slightly better. And both the canon and Tamron have a constant f2.8 aperture, which is very, very nice and much more versatile than the 15-85's variable, and relatively slow, aperture.

[neuroanatomist]

Surely the Canon 15-85mm gives better IQ and functionality than the Canon 17-55mm and the Tamron 17-50mm anyway?

Yes, it has a broader focal range. If that were all that mattered, we'd all be using the Tamron 18-270mm on APS-C, right? Why would anyone pay close to $2K for the 85mm f/1.2 - it's only got one focal length! </sarcasm>

There are three factors to consider between the two: focal length, aperture, and IQ. As you stated, the 15-85 wins on focal length. The aperture goes to the 17-55mm. The variable aperture of the 15-85 changes like this:

15-17mm = f/3.5
18-26mm = f/4.0
27-37mm = f/4.5
38-60mm = f/5.0
61-85mm = f/5.6

So, by 18mm it's letting in only half as much light, and by 38mm it's 1.67 stops slower. That means less ability to stop action, and less subject isolation (the 17-55mm is good for portraits, the 15-85 much less so). The IQ is close, but the edge goes to the 17-55mm - it has less distortion (broader zoom range means more distortion), and less vignetting (despite the wider aperture). Sharpness is similar, but while distortion and vignetting can be corrected in post, there's a cost for that - reduced sharpness and increased noise.

I usually recommend the 17-55mm over the 15-85mm because it's more versatile. If you will do almost all of your shooting outside in good light, or don't mind using a flash indoors (and not the popup, please!), the 15-85mm is a good option. The 17-55mm allows stopping action in less light and delivers shallower DoF for portraits, which IMO makes it more versatile.

[Kayaker72]

Surely the Canon 15-85mm gives better IQ and functionality than the Canon 17-55mm and the Tamron 17-50mm anyway?

I own and highly recommend the EFS 15-85. However, I have to agree with thekingb and Neuro and wouldn't say that it "gives better IQ and functionality" than the 17-55 or the Tamron 17-50 non-VC (which I understand to be better than the VC version). I have studied the Tamron much less, but in general, I would say that all three of these lenses are used and well liked by different members of the forum. Understand that no lens is perfect, but these are three very good lenses (again, I am more familiar with the Canons) from a cropped sensor body.

As has already been pointed out, if anything, the 17-55 may have slightly better IQ than the 15-85. That said, you will likely only be able to tell that by looking at reviews and even then it is very slight. In real world shooting, the IQ of these lenses is very good to excellent.

Which is "better" in terms of functionality depends the the function. IMO, the case for one of the f/2.8 lenses, especially the EFS 17-55, has already been well made. And I am not posting to disagree. From everything I have read, heard and seen, it is an excellent lens.

But I wanted to chime in with two points:

1) The difference between 15 to 17 mm focal length is noticeable. 15 mm on a crop body is equivalent to ~84 degrees diagonal angle of view (AOV) vs ~77 degrees at 17 mm. That is a 9 percent difference. On the long end, 50 mm has a AOV of ~30 degrees vs ~18 degrees for 85 mm. Also, adjusting 50 mm and 85 mm to full frame equivalents you get 80 mm and 136 mm, which happens to be the classic "portrait" range. That extra range is very useful and, as is common, I do tend to shoot most at the extremes (near 15 mm and near 85 mm) of my EFS 15-85.

2) While f/2.8 will give you 2/3 to 1 2/3 more light in comparison to the 15-85 at similar focal length and exposure settings, it often isn't enough to shoot in low and moderately lit conditions. In lower light I have found f/1.8 to not be enough to "stop action." So, you will likely still need a flash if you are shooting in low to moderate lit conditions.

Getting back to functionality, there are a lot of "functions" within photography and these three lenses will perform very well for most of them. But, the aperture/focal length trade off does favor each lens for certain specific functions. For example, I would recommend one of the f/2.8 lenses to someone that will be taking the time to set up a subject when the thin DOF can really be taken advantage of (say for portrait photography) or for someone that has a family and will want to "stop action" of kids running around the house. For those functions, I think the benefit from the aperture is worth the sacrifice of the focal length range. But then I view the focal length advantage being better for people that want a "general" general purpose lens. For example, I shoot a little of everything and I love being able to leave the EFS 15-85 on my camera for most of it. It is a great walk around lens and covers a wide range with a single lens very well.

Good luck.

[Dr Croubie]

I've also got the 15-85 and love it, I just don't use it as much as I should these days, because I'm not really travelling.
In short, the 15-85 is a 'travel' and 'outdoors' lens, the 17-55 f/2.8 (or equivalent) is better for indoors and at night, the IQ on both of them is past the point of "good enough" for most cases.

I've ended up with primes that overlap it in that range, the Samyang 35/1.4, Asahi Takumar 50/1.4, EF 50/1.8 II, EF 85/1.8, and if you've got the cash I'd definitely recommend the route of the 'travel' 15-85 and 'low-light' fast primes.
If I'd gone with the 17-55 f/2.8, that's great for low-light, and it may have been the only lens i'd gotten and not bothered with the f/1.8 primes, you only gain a stop and a bit from f/2.8 to f/1.8. But going from the EFs 15-85, f/5.6 to f/1.8 at 85mm is a ridiculous improvement. Rarely do I want anything faster at 85mm if i'm out travelling or hiking (where I'd only bring anything wider than the 70-300 for landscapes anyway, when I'd stop down to f/8 anyway).

So the 15-85 may be a 'do-it-all' lens in one sense, because of the focal-length-range, but in another way the 17-55/2.8 is more 'do-it-all', because you can take portraits as well as landscapes with it, and you don't "need" primes as badly as you do if you go the 15-85 and want to take portraits too (and can't justify extra cash for the amount of times you take them).

And to agree with kayaker, a flash is very useful no matter how fast the lens. I spent most of xmas day with my 7D with 430EX mounted on the top with cheap $5 chinese ebay softbox, switching between the samyang 35/1.4, takumar 50/1.4, ef 85/1.8 taking shots of kids running around unwrapping presents, using the flash I kept it on M at iso100, 1/200s, f/2-2.8 or so for extra DOF, and let the flassh fill in any extra holes where it was too dark.

So definitely, think about your use-scenarios, if you see a bit of indoor use with kids running around, and only have limited money ("this will be my only lens" scenario), the 17-55 f/2.8 may be the way to go. If you're going to travel and/or want a lot better quality in low-light, go the 15-85 and get primes later. Or go the 17-55/2.8 and get primes too, but you're missing out on the widest end and may need an 8-16/11-16 or so further down the track.

[ddt0725]

I have owned the Canon 17-55mm and I now have the Tamron 17-50 non-VC and I am extremely pleased with it. When I look at my photos taken with each, I do not see any difference in IQ. Do I miss my 17-55mm? You betcha! Why? Heck, because it's a Canon! It's just the psychological aspect of it, knowing I once had the Canon and now I have the Tamron. Of course, Canon's IS is an awesome thing but it comes at one heck of a price tag. Close to what you would pay for a Canon 17-55mm IS, you could get the Tamron 17-50 non-VC, a non-Canon ultra-wide (which I think Bryan gave a thumbs up on the Sigma 8-16mm) and a 430ex II! If you bought any of them used or refurbished, you would still have money left over!

Denise

EDIT: Oops, forgot to mention that I too started with the 300mm for birding and soon switched to the 100-400mm for the same reasons as Neuro. 300mm is definitely not long enough for birding in the wild and as time goes on, I am becoming more and more frustrated with 400mm still not being enough. Just a couple days ago, I couldn't believe how many BIF I hit my focus right on the mark but when I got home and got them on my computer, most ended up in the recycle bin because after cropping they weren't worth keeping.

[Steve U]

Trying to stay on topic, because the OP mentioned the Sigma 150-500mm was a consideration at some stage. Well along that line, there is talk that Sigma may be releasing a new version of their 500mm F4.5, at perhaps f4. This will definitely put the cat amongst Canon's big tele's as the Sigma OS is every bit as good as the Canon's and Sigma glass just keeps getting better and it is a lot more affordable.
Will see what 2012 brings as far as new announcements go...

[qwRad]

I will be extremely interested in a Sigma 500mm f/4.5 (or even better if f/4) OS lens since I briefly tested the 120-300mm f/2.8 OS and it was quite awesome except for the humongous size. I ended up with the 70-200mm f/2.8 IS II for portability but the price was only a little cheaper than the Sigma and reading the reviews the IQ of the new Sigma is supposed to be very nice.