15-85mm f/3.5-5.6 vs 17-40mm f/4L for a crop camera

[elflord]

Keep in mind that 2.8 vs 4.0 is only one stop difference. For real low light shoots you need to get one of the fast primes (50mm, 35mm, 24mm)

At the long end it's f/5.6 (2 stops). At 55mm, it's f/5 (1 2/3 stops). f/2.8 isn't just an advantage for low light -- you can still get reasonably shallow dof at 55mm f/2.8 on a crop, whereas the 15-85mm is pretty much an "f/8 and be there" lens.

[neuroanatomist]

Keep in mind that 2.8 vs 4.0 is only one stop difference. For real low light shoots you need to get one of the fast primes (50mm, 35mm, 24mm)

At the long end it's f/5.6 (2 stops). At 55mm, it's f/5 (1 2/3 stops). f/2.8 isn't just an advantage for low light -- you can still get reasonably shallow dof at 55mm f/2.8 on a crop, whereas the 15-85mm is pretty much an "f/8 and be there" lens.

Agreed, which is why I prefer the 17-55mm - it does pretty well as a portrait lens, too, whereas the 15-85mm often cannot deliver sufficient OOF blur for the desired framing, because of the narrower aperture.  The wider aperture also allows faster shutter speeds when needed.  To me, that makes the 17-55mm a better general purpose zoom - outdoors and indoors, landscapes, action and portraits, vs. the 15-85mm which is more suited to outdoors and landscapes.

[paulc]

My main problem with the 15-85mm, is the lens creep. I'm really afraid of that.

Lens creep is an annoyance, not an actual problem.  The only exception to this is tripod work where you're pointing up or down.  I've got the 28-135, the creepiest of the creepers and I'm still alive.

Don't fear the creeper. 

[RC]

My main problem with the 15-85mm, is the lens creep. I'm really afraid of that.

Had a new 15-85 and lens creep only occurred very little and that was when I was pointing the lens straight up such as moon shots.  Sold it because I needed weather sealing with my 7D. 

[sawsedge]

I replaced my 17-40 with the 15-85 for the range.  I wanted something a little wider, and a little longer.  The tradeoff is losing a stop of speed.  Outdoors this isn't a problem.

I have no zoom creep.

The 15-85 is sharp from corner to corner wide open at every setting (there is a tiny bit of loss of sharpness in the very extreme corner which doesn't affect most real-world images).  Bokeh is quite decent, as is color and contrast.

I wish it was weather sealed, and faster, but the image quality can't be beat.

[unfocused]

This really shouldn't be that difficult of a decision. Buy the 15-85mm.

The quality of the glass is excellent. The zoom range covers all the most-used focal lengths from 24mm to 135mm. It's affordable and has very good IS. It's a substantial lens with good, solid build-quality that can withstand lots of banging around.

Would I prefer a 15-85mm f4 constant aperture? Yes, but they don't make that one – yet.

Zoom creep on mine is horrible. But I can't for the life of me understand why anyone would be "afraid" of zoom creep. It's at worst an inconvenience. If you are shooting something straight up or straight down, just hold on to the zoom ring when shooting. Not that difficult. In normal use, you are going to be looking through the viewfinder to frame the subject before shooting so it really doesn't matter if the lens has zoomed itself in, just zoom it back out. Again, not that difficult.

[ecka]

Keep in mind that 2.8 vs 4.0 is only one stop difference. For real low light shoots you need to get one of the fast primes (50mm, 35mm, 24mm)

At the long end it's f/5.6 (2 stops). At 55mm, it's f/5 (1 2/3 stops). f/2.8 isn't just an advantage for low light -- you can still get reasonably shallow dof at 55mm f/2.8 on a crop, whereas the 15-85mm is pretty much an "f/8 and be there" lens.

17-55 must be stopped down to at least f/4 to match the sharpness of the 15-85 wide open. It's not an f/8 lens really.

This really shouldn't be that difficult of a decision. Buy the 15-85mm.

The quality of the glass is excellent. The zoom range covers all the most-used focal lengths from 24mm to 135mm. It's affordable and has very good IS. It's a substantial lens with good, solid build-quality that can withstand lots of banging around.

Would I prefer a 15-85mm f4 constant aperture? Yes, but they don't make that one – yet.

Zoom creep on mine is horrible. But I can't for the life of me understand why anyone would be "afraid" of zoom creep. It's at worst an inconvenience. If you are shooting something straight up or straight down, just hold on to the zoom ring when shooting. Not that difficult. In normal use, you are going to be looking through the viewfinder to frame the subject before shooting so it really doesn't matter if the lens has zoomed itself in, just zoom it back out. Again, not that difficult.

+1

[elflord]

17-55 must be stopped down to at least f/4 to match the sharpness of the 15-85 wide open. It's not an f/8 lens really.

I'm not saying that the 15-85mm needs to be stopped down to perform adequately, I'm saying that even "wide open" (or as open as it can go), it doesn't have very shallow depth of field. At the tele end of its range, it is depth-of-field equivalent to f/8 or f/9 on a full frame, which is what motivated my reference to "f/8 and be there".

I agree that it performs pretty well at its maximum apertures. It's is a slow zoom, but as far as slow zooms go, it's pretty good.

[lol]

The original question was a choice of either the 17-40 or 15-85. Neither develop much shallow depth of field. And if you really wanted shallow depth of field, you could consider the 50mm f/1.8 in addition to the 15-85 which combined still costs less than the 17-55 by itself.

[LuCoOc]

Keep in mind that 2.8 vs 4.0 is only one stop difference. For real low light shoots you need to get one of the fast primes (50mm, 35mm, 24mm)

At the long end it's f/5.6 (2 stops). At 55mm, it's f/5 (1 2/3 stops). f/2.8 isn't just an advantage for low light -- you can still get reasonably shallow dof at 55mm f/2.8 on a crop, whereas the 15-85mm is pretty much an "f/8 and be there" lens.

Agreed, which is why I prefer the 17-55mm - it does pretty well as a portrait lens, too, whereas the 15-85mm often cannot deliver sufficient OOF blur for the desired framing, because of the narrower aperture.  The wider aperture also allows faster shutter speeds when needed.  To me, that makes the 17-55mm a better general purpose zoom - outdoors and indoors, landscapes, action and portraits, vs. the 15-85mm which is more suited to outdoors and landscapes.

Oops! Tatally agree with you two... kinda mixed the 3 lenses in this thread. Anyway, get the 15-85 and if neccessary a flash (430 EX II?) for indoor use.

[ecka]

17-55 must be stopped down to at least f/4 to match the sharpness of the 15-85 wide open. It's not an f/8 lens really.

I'm not saying that the 15-85mm needs to be stopped down to perform adequately, I'm saying that even "wide open" (or as open as it can go), it doesn't have very shallow depth of field. At the tele end of its range, it is depth-of-field equivalent to f/8 or f/9 on a full frame, which is what motivated my reference to "f/8 and be there".

I agree that it performs pretty well at its maximum apertures. It's is a slow zoom, but as far as slow zooms go, it's pretty good.

Well, then 17-55 is pretty much an f/4 or f/4.5 lens (FF equivalent) , isn't it?
I do agree that 17-55 f/2.8 aperture is a strong point against 15-85, but it is out of the OP's budget. So ... why arguing?
You can get 15-85 + 430EXII for less than 17-55 alone.

[Mt Spokane Photography]

I've had a 17-40, 17-55, 24-105, and now use a 15-85mm on my crop camera.

The 17-55 is a great lens, but for outdoor and good light, the wider range of the 15-85 is very nice.  I personally did not like the 17-40 on a crop, or on my 5D MK II as well.  It just seemed to lack something.

A 24-105mm L is excellent on both crop and FF, but I found 24mm to often be too long on a crop.

You will not go wrong with any of the lenses its just matching the aperture and focal length to what you need.

[AJ]

So, now I have a new question. How about the Tamron 17-50mm vs the Canon 15-85mm

Really depends on what you're using the lens for (if you want f/2.8 or the longer range). If you're using it indoors, the Tamron. For an outdoor walkaround, the 15-85.

^^^ this

If you want to shoot selective focus with crop gear you'll need a fast prime, or something like a fast 70-200.  Don't count on your standard zoom, neither 17-55 nor 15-85 delivers much blur.

[neuroanatomist]

17-55 must be stopped down to at least f/4 to match the sharpness of the 15-85 wide open. It's not an f/8 lens really.

How do you figure that?  Wide open, they have similar center sharpness through the range, and away from the center, the 17-55mm is sharper.  Plus, wide open is wider on the 17-55mm. Also, sharpness isn't everything. The 17-55mm has less distortion and less vignetting, and while those can easily be corrected in post, proper correction of the distortion at 15mm means you're not getting a 15mm AoV, and the corrections also mean even softer (and noisier) corners.  But really, the differences in IQ are minor, and shouldn't be the deciding factor. Rather, it's a trade off between aperture and focal range, and of course, budget.

[Radiating]

Again, I've posted here before asking about different lens. So now I'm being a little realistic.

Rather than purchasing 24-105, I'm thinking about getting the 17-40mm as a replacement for my kit lens.

Which lens is going to be a better replacement for my 18-55mm?

If you do have another suggestion, I'd like to hear it as well. But my price range is from $500 - $800.

(Side note, I do not plan on going FF. I do plan on upgrading to a 7d though, even though it's still a crop sensor camera)

This should really be a simple decision. The 17-40mm L is the absolute worst choice you could possibly have on a crop body. That lens is only useful on full frame. The reason is that is virtually idencial performance to the 18-55mm IS kit lens, while having significantly less features in many key areas. Canon makes an amazing kit lens for it's crop bodies. The 15-85mm is one of the best lenes around though.