17-55 Aperture Advantage 2.8 New to DSLR

Hi there

I am a beginner by every means, had my 650D for around a year now. Know about settings and aperture and iso and everything.

When it comes to deciding between a fast lens (2.8 or 1.8 and so on) and another lens say 3.5 or f4 and higher. The latter being better in low light photography. Is that just low light hand held? I see many incredible photos taken with the 17-55 and many say due to its 2.8 aperture its better than say a slower 15-85 in some instances. All the great pictures I see during low light are sitting at f9-f11. So the low advantage over another lens goes out the window?

I have other threads deciding between lenses, do not wish to double post questions but the aperture part over more reach must then apply to hand held getting higher ISO and shutter speeds?

If so I could get a lens with more reach thats slower and use a tripod in the later evenings or indoors. Do not need it for sport or video just still photography.

If you're shooting at f/5.6 or smaller (larger f-number), then both lenses will give very similar result. Both the 17-55/2.8 and 15-85/3.5-5.6 have image stabilization to help hand-holding in low light with long shutter speeds.

The viewfinder AF works with aperture wide open, and many EOS cameras will AF with greater precision with f/2.8 and wider maximum apertures. And f/2.8 zooms often have more lens elements with better correction of optical aberrations than do f/3.5-5.6 zooms. Despite the shorter zoom range, the 17-55 has 19 lens elements (2 are Ultra-low Dispersion) compared to the 15-85's 17 lens elements using 1 Ultra-low Dispersion element.

Shooting the image with f/2.8 and larger aperture allows you to

• give shallower depth of field, separating your subject from the background
• use a higher shutter speed at the same ISO to freeze motion - both the subject's and yours if shooting hand-held

No right answer, both are very fine lenses. I chose the 15-85. YMMV.

Lemming51 wrote:

If you're shooting at f/5.6 or smaller (larger f-number), then both lenses will give very similar result. Both the 17-55/2.8 and 15-85/3.5-5.6 have image stabilization to help hand-holding in low light with long shutter speeds.

The viewfinder AF works with aperture wide open, and many EOS cameras will AF with greater precision with f/2.8 and wider maximum apertures. And f/2.8 zooms often have more lens elements with better correction of optical aberrations than do f/3.5-5.6 zooms. Despite the shorter zoom range, the 17-55 has 19 lens elements (2 are Ultra-low Dispersion) compared to the 15-85's 17 lens elements using 1 Ultra-low Dispersion element.

Shooting the image with f/2.8 and larger aperture allows you to

• give shallower depth of field, separating your subject from the background
• use a higher shutter speed at the same ISO to freeze motion - both the subject's and yours if shooting hand-held

No right answer, both are very fine lenses. I chose the 15-85. YMMV.

Thanks very much for the detailed reply, Nice to get some solid facts behind the decision. Cant believe it's been so difficult to choose between the two lenses! I actually went out this evening (SA time) and shot with the 50 1.8 but set to 2.8 to kind of see how it handled the light and I must say in some dark (ish) places not too well. That made me realise that maybe 2.8 is not even fast enough for very low light and perhaps the choice should be 15-85 with a tripod for evenings and night. The only thing that slightly bugs me is the DOF and perhaps not being able to get as creative images out of the 15-85 as I would with the 17-55. I do have a point and shoot for general pictures I need a lens that will allow me to get creative looking images with high IQ, although maybe i need to study more techniques and learn how to shoot at all the different lengths the 15-85 allows.

SeanGrey wrote:

Hi there

I am a beginner by every means, had my 650D for around a year now. Know about settings and aperture and iso and everything.

When it comes to deciding between a fast lens (2.8 or 1.8 and so on) and another lens say 3.5 or f4 and higher. The latter being better in low light photography. Is that just low light hand held? I see many incredible photos taken with the 17-55 and many say due to its 2.8 aperture its better than say a slower 15-85 in some instances. All the great pictures I see during low light are sitting at f9-f11. So the low advantage over another lens goes out the window?

I have other threads deciding between lenses, do not wish to double post questions but the aperture part over more reach must then apply to hand held getting higher ISO and shutter speeds?

If so I could get a lens with more reach thats slower and use a tripod in the later evenings or indoors. Do not need it for sport or video just still photography.

As Lemming51 alluded to, there's no right answer. What I can say for myself is that I wouldn't be without a fast medium range lens. Having had both (or having both) and more, I would stick with less focal range to have a faster lens. But, I shoot a lot of low light environments, so this is the way I'm biased. Before this I was perfectly happy with the precursor to the 15-85 (EF-S 17-85)

Don't discount the third party lenses, which can be had for a lot less than the 17-55 and are every bit as sharp. The Tamron 17-50 (non-VC) is very sharp.

This is the EF 24-70/2.8 II on my 70D. It's at or above 1900 resolution on this chart (Reikan FoCal), with a dropoff at 2.8. Otherwise, the only other lens I have that beats it is my 100/2.8L IS Macro

However, the lowly Sigma 17-50/2.8 OS bests it at 2.8 and 3.5, and is awfully close elsewhere. This is amazing performance for a $500ish lens.

You already know the pros and cons of a 2.8 or faster lens. The difference between this and F4-5.6 is quite apparent when you're up against having to dial up your ISO or not. Of course at a distance, the DOF is less apparent and less of an issue.

IS is really helpful, and makes a huge difference when shooting. I usually find it to make up for at least 1 if not 2 stops in real life shooting, which is a lot. But, it won't stop your subjects if they're moving. That's the limitation of stabilization. F2.8 will allow you to use a faster shutter speed, and this is even noticeable if you've got a flash (which I highly suggest at some point).

Once I got my 6D I found that F4 would really suffice for many situations, but I'm sure glad I have this faster glass for my crop cameras still.

Thanks for the stats, a few people actually told me to look at the 17-50 sigma too! Looks like a very good choice at a much lower price. It's just the 17-55 2.8 here in Cape Town is on special for R8500 ($715) and for tweaking the manual focus ring full time and it not moving when you auto focus would be nice feature if Im spending allot on a lens.

I'm still doing tons of research but a thought of mine earlier..

I have dogs and enjoy photographing them too, one being an Italian greyhound puppy who without 2.8 at least Im afraid I would miss. I also want a 70-200f4is one day for sport and a 100 1.8 for macro so don't really mind swapping lenses and carrying a few with me. Iv got a 50 1.8 too for other shots and If i ever get into landscape I would probably go for a cheaper 10-18 for the super wide angle. I think then after reading your reply and what I have just written it sounds like the canon 17-552.8 would suit me and I wouldn't miss the 15,16 and 55-85 range along with lower speed, better build and less dust vacuuming.