I'm debating between the 24-70 f2.8 or the 24-105 f4.0 IS for the mid-focal length... I know many say the image quality of the 24-70 is better.

My question is which will get me sharper images, in all light conditions? - based on the fact that I have somewhat shaky hands.

Does the IS give me the ability to go to even faster shutter speeds than the f2.8 would in low light? Does the IS make ~1/100 shutter speed images tack-sharp while without IS they could be slightly blurry if I'm moving?

Thanks for any insight!

IS is designed to counter shaky hands. It doesn't freeze subject motion. So, if you are going to shoot a static subject at lets say 1/30, 70mm, f/4 chances are that the 24-105L will generate sharper images. If your subjects are moving, the 2.8 aperture will be more beneficial, because this will gain you a full stop of shutterspeed. The higher the shutterspeed, the more effective the motion freezing will be. In this case the 24-105L's IS won't help you and the f/4 may be too slow for a lot of circumstances.

I don't know how shaky your hands are so it's hard for me or anyone to really answer this question with a "you should get A" answer.

IS doesn't allow "faster shutter speed". Rather it allows you to use slower while still have a higher chance of getting a good image. Keep in mind that IS doesn't stop motion. So if you have IS and you shoot at a slow shutter speed you can have sharp stationary objects but people in the picture who are moving will become blurry.

Also keep in mind that the focal length also makes a difference. In general the rule of thumb for non-IS shooting is 1/F. So if you are shooting at 24mm you generally need 1/24 shutter speed to get a good image. And for stopping motion the faster the shutter speed the faster the motion that can be frozen. Most people say for general sports you need 1/500 or higher (as far as I can recall).

My own personal preference is wider aperture over IS but I like having both. And my own experience with the 24-105 (no opinion on the 24-70 as I haven't had the pleasure of owning it) is that f4 is a bit too slow for night time indoors applications without flash.

Thanks Daan, I see what you're saying. That was my thinking. I shoot mostly static frames.

gotak - " In general the rule of thumb for non-IS shooting is 1/F. So if you are shooting at 24mm you generally need 1/24 shutter speed to get a good image." That seems like a very sweeping rule - I can't imagine 1/24th getting a very good imagine when the sun is blasting your frame on a nice day - unless I stopped way way down?

My hands aren't THAT shaky - but I do miss more shots than I'd like when the light starts to get dim.

1/FL is an old and outdated rule based on not printing larger than 8X10 and shooting film. Double it at least for modern DSLR's IMO.

If you have very shaky hands, then the 24-105 is the way to go.

I'm fairly shaky myself, but don't have that issue with the 24-70. I start to notice it with the 135/2, though.

I hate to say this but, do you use a tripod?

I shoot with two friends who have a palsy and they have both developed techniques which allow them to shoot free hand. However, they defer to the tripod whenever they can.

In addition we have all committed to IR remotes which are very affordable.

IF you don't like a tripod or monopod then try a Bushhawk.

I do use a tripod when I can /w a remote - but very often it's just not practical. Again - not terribly shaky.

DavidP, what do you mean you start to notice it with the 135f2? Because of the longer focal length?

I like my 24-105L very much on my 40D. The IS is helpful alot of the times but it has to be said that it doesn't substitute more light entering the lens.
I had a 28-70 2.8 before and while I would like the 24-70 I may just try and add a couple of fast primes to my bag

I don't have shaky hands, but find that using a tripod is a real boon to getting better images of static subjects. A tripod can be inconvenient at times, but it is sort of like eating your vegetables when you were a kid, or moving the focus button to the back of camera with CF-4. If you force yourself to hold your nose and use a tripod for a few sessions of static shots it does become second nature and the end product will improve.

f/2.8 would give you one more stop of shutter speed over f/4. IME IS would help more than one stop. So if you don't need fast shutter speed or shallow DOF, in theory 24-105L would help you suck in more light while giving you a sharper image.

Look at it another way. How often do you shoot at f/2.8? I own both lenses. Even so, I don't shoot at f/2.8 all the time - most of my everyday shooting is done at f/8 to f/16. At these apertures, the IQ from both lenses is effectively identical. In that case the only difference between the two is one lense has IS and one doesn't. Which one do you think I reach for most often? With IS I can (and often do) shoot from a moving vehicle and still get sharp results. I can shoot with polarizers or ND filters and not worry about slowing down the shutter.

Yes, when I need f/2.8 there is obviously only one lense I can got to, but usually when I'm shooting at that aperture I find I'm taking more time to slow down and compose the shot anyway, and the higher shutter speeds also compensate. But for shooting on the fly, IS definitely is a life saver!

jkickhofel wrote:
DavidP, what do you mean you start to notice it with the 135f2? Because of the longer focal length?

Yep

jkickhofel wrote:
My question is which will get me sharper images, in all light conditions? - based on the fact that I have somewhat shaky hands.


24-105L will give deliver you sharper image. The usefulness of IS really shines when you shoot stationary objects @ slower shutter. Not only you get more DOF(desirable or not) chances are your picture will come out more focus and sharper than 24-70L.

Thanks for the advice everyone. matanuska, you put it perfectly - IS can help me out in all situations, not just f/2.8 low light, I felt this was true.

As someone who made the decision to go with the F4, I did so not because of shaky hands (although I'm sure I have it as much as the next person). During the day I didn't notice any image quality difference of the F2.8 vs the F4, and at night I realized I would need a tripod no matter what. I did find the F2.8 gave that "edge" handheld...but out of 10 shots I may get one shot with the F4 and two shots with the F2.8, so I decided to offload the F2.8 since the F4 was lighter, added more focal length, and had IS.

It should be pointed out that there's more distortion in the 24-105. For most things, though, this isn't a real problem, IMO.

Both are sharp, but the 24-105 IS will definitely let you shoot at lower shutter speeds for static scenes.

If you're on a crop-body, how about considering the 17-55mm f/2.8 IS?