EF-S 17-55 f/2.8 vs. EF-S 15-85 f/3.5-5.6

[vnavone]

I'm looking to upgrade from my kit lens and I'm torn between these two. My instinct is to go with the 17-55 because it's a faster lens and I do a lot of indoor, low-light shooting. My hesitation is that when comparing the two lenses in the ISO 12233 test, the 15-85 looks far superior across the frame in sharpness, contrast, vignetting and CA:


http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?CameraComp=0&FLIComp=0&APIComp= 0&Lens=398&Camera=474&Sample=0&FLI =0&API=0&LensComp=675


When I read the respective reviews, the 17-55 is regarded as having slightly superior image quality. Am I missing something? Any advice appreciated!


Canon T2i body, 18-55 kit lens



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[neuroanatomist]

I'd say that the 17-55mm has overall very slightly superior image quality. Keep in mind that those summary statements are just that - overall impressions. In the example you showed, the 15-85mm is a little sharper. The 15-85mm seems to have a little more vignetting wide open at the wide end, for example. The 15-85mm has more barrel distortion at the wide end than the 17-55mm.


Bottom line is that from an optical performance standpoint, the two lenses are more alike than different, so basing the decision on things like sharpness and vignetting is splitting hairs.


What it should really come down to is whether you need a constant f/2.8, or are willing to trade that fast aperture for some extra focal length on both ends and a lower cost. If you're shooting a lot of indoor, low-light shots you'll want f/2.8 (and even then that's not enough sometimes, which is where the faster primes come into play).

[Daniel Browning]

The 17-55 is the one lens where Bryan specifically mentioned that it seemed to underperform on the tests compared to real life. There are several possible explanations for this -- curvature of field (which affects tests more than real life), worse performance at close focus distance, etc. Another possibility is that the 15-85 really is just sharper. In that case you

[DLS]

Welcome vnavone, to the forums.


Here's my two bits....

. If you're shooting a lot of indoor, low-light shots you'll want f/2.8 (and even then that's not enough sometimes, which is where the faster primes come into play).
<p style="CLEAR: both"]

<p style="CLEAR: both"]I second neuro. If you shoot mainly indoors you'll definitely need f/2.8 and then some. Coming from the kit lens you will be happy with the wider max aperture of 2.8.When I went from aRebel kit lens to a 50 f/1.4 Iwas very pleased with low light ability, althoughon a crop body shootingindoor with the 50 f/1.4can be quite tight sometimes(in a house, that is, unless your househas large rooms, ha ha).Have you considered any of the wide primes for indoor shooting?
<p style="CLEAR: both"]Damian

[Kayaker72]

vnavone,


A lot of people in this forum own and tend to think very highly of the EFS 17-55. I own and think very highly of my EFS 15-85. One thought on the ISO 12233 chart example you posted is that you may want to compare the lenses at similar focal lengths and the same aperture. I believe you compared 15 mm and f3.5 for the 15-85 to 17 mm and f2.8 for the 17-55. While that is close, stopping down even a little does give an advantage to the 15-85. But if you compare each at f4, for example, you will see the IQ under similar shooting conditions.


I chose the 15-85 because I wanted the focal length range andthe cost of each lens was a slight factor (I bought mine when there was an instant rebate). I figured I could buy a fast prime for indoor shooting with the price difference and I did buy the 50 f1.8. But, in my experience thus far, I leave the 15-85 on the camera and shoot non-moving subjects with slow shutter speeds thanks to the IS and use a flash for moving subjects.


The 17-55 will let in ~1.5x and ~3.2x the amount of light at 17 and 55 mm, respectively, as the 15-85. Whether that is enough, as Damian and Neuro said, depends upon how much ambient light you have. One advantage of the 17-55 in every situation; you can get much better depth of field with f2.8 (see the Assignment 14 thread) than you can with f3.5-5.6. Depending on what you are shooting, that can be a big deal.


My opinion is that these are two good lenses. It really depends on if you want flexibility in focal length or aperture. But I wouldn't worry about IQ. From what I've seen they are very similar.


I hope that helps.


Brant

[vnavone]

Thanks for the feedback. I

[Trondster]

When you do compare image quality between the two - do compare them at the same aperture! Set both to f/4 at the wide end, and the results are not that different anymore:


www.the-digital-picture.com/.../ISO-12233-Sample-Crops.aspx

[neuroanatomist]

That does get a little tricky, since at f/4 the 17-55mm is stopped down a full stop from wide open, whereas the 15-85mm is only stopped down 1/3 of a stop from wide open. Since stopping down improves performance (usually, and only out to a certain point before diffraction rears it's ugly head), that makes comparing lenses with different maximum apertures somewhat imprecise.

[Trondster]

Not really. Just compare the lenses at the same aperture, check the performance of the faster lens at the larger aperture, and take into account that you have the option to use a faster aperture than the slower lens. Not that different from comparing lenses with different zoom ranges.


The 17-55 is about as sharp as 15-85 - with 17-55 you have the option of using a larger aperture, and with 15-85 you have the option of using a larger interval of focal lengths.


However, do consider that the faster lens probably will focus a bit better in low light, as well as a bit more precisely, due to being able to focus at a larger maximum aperture.


I

[George Slusher]

I have a 17-55 and will get a 15-85, probably in January or February. I used to have a 17-85, but it was stolen (along with a 70-200 f-2.8L IS, 100-400, Sigma 10-20, 100 f2.8 macro, 1.4 extender, &amp; a camcorder, plus two Think Tank bags &amp; other stuff). I found both the 17-55 &amp; 17-85 useful, but for different purposes. (I realize that the 17-85 is NOT the same quality as the 17-55 or 15-85!) The 17-85 was a great "walking around" lens. For nature shots, it complemented the 100-400 (&amp; sometimes the 10-22). I'll use the 15-85 the same way, though the 100-400 has been replaced by a Sigma 120-400.


I also photograph at horse shows. For some outdoor shows, the 17-85 worked well, along with a 70-200 f/4L IS. (Yes, I had both 70-200's: I got the f/4 first, then added the f/2.8.) Those don't work for indoor shows, though. At first, I used prime lenses: 35 f2, 50 f1.8 (later f1.4) &amp; 85 f1.8. That was OK, especially if I could concentrate on one spot--a particular jump, a barrel in barrel racing, etc. However, a zoom was nice, as the distance can vary a lot. With f2.8, I can barely get a satisfactory shutter speed (1/250, min--1/400 is better) @ ISO 1600 on my 30D. (I can go to ISO 3200, but the noise is much worse.) I still use prime lenses for high-speed events, but the f2.8 zoom is useful for everything else. I just bought a used 50D on eBay ($706 including the BG-E2N grip!) and may be able to use ISO 3200 more of the time, making the f2.8 zooms more useful.