IS vs IQ

[sublime LightWorks]

So am wondering why many believe that IS on a lens reduces picture quality??

Lots of reasons. First off, it depends on the lens. For example, the 70-200/2.8L non-IS is actually sharper than the 70-200mm/2.8L IS (original) - so in some cases, it's true. Then people extend that logic to other lenses, even though each lens design is unique.

Also, it depends on usage. For example, the IS system in some lenses, like your 24-105mm, is not tripod-sensing. If you leave it on when shooting from a tripod, the IS system will try to compensate for the (almost) nonexistent vibrations, and actually introduce a loss of sharpness to the image by doing so.

That begs the question....what's the sharpness comparison if you switch off the IS?

I hear you on the diff between the non-IS and IS rev1 versions of the 70-200mm f/2.8. Having owned both, I saw that first hand. The new 70-200 IS rev2 is another story....

I never tested the original 70-200 with IS switched off, BUT I have shot the new with IS off and can say under several conditions I have obtained even sharper images with IS off. Several have been on moving targets (equestrian jumping) where previously I had panning IS enabled.

There are times when I will shoot sports for a while with IS on and with IS off, if the targets are moving at a good clip. Professional cycling is a good example, especially in individual time trials. The results can surprise you. I've taken to not using IS if the target is fast moving and using IS if its slower moving or stationary.

EDIT: don't mistake my comments here on fast moving targets as some expectation on my part that IS is supposed to help in stopping motion. I'm fully aware it's not, the comments are more towards stability of the image and smoother tracking. Finding that with IS off while shooting a fast moving object tends to render sharper images is just an observation. In addition, having a well practiced panning shooting skill is vital.

 

[Marsu42]

Part of what you are missing is the point I was trying to make, which is can a lens with NO IS be inherently SHARPER, with less CA and other defects across ranges.

I didn't miss the point - I just think there's no real answer to that: It depends on the company's ip (is technology), their experience with is and their manufacturing processes. If a company got that right, I guess an is lens is just as good as a non-is lens; I agree there's a lot of nostalgia floating around from the good ol' days.

 

[wickidwombat]

One of the reasons I think you don't see the 24-70 with IS is the short range of the lens, as well since it is capable at F/2.8 and looks like it does not have to be stopped down to be affective

I don't understand why people seem to think that f2.8 is *always* better than f4 and above - in many situations, the dof of f2.8 larger apertures is just too thin, and the bokeh of f4 is ok too if there's no irritating object directly behind the dof pane. This is definitely true for my macro lens: 2.8 is just ridiculous if your object is not a flat piece of paper.

Of course I want a medium tele lens with IS - then I can shoot static objects with large dof at iso 100 and no noise! The only reason the 24-70 has no IS seem to be weight considerations - which I can understand given the weight of a 70-200/2.8is2.

Does IS make a noticeable difference shooting hand held at above 1/60th at a distance of under 20 feet with a focal length of under 70?

IS gives more good shots, nothing more - or said the other way round: If you have enough time you can just take a picture burst, one of them usually will be sharp. With a lens w/o IS you can get crystal sharp images, because your hands move from one point and back - at the peak of this sine curve your hand is steady like a tripod. If the shot is steady, only the lens sharpness matters (if you've got a good copy, that is).

f2.8 and faster lenses focus faster and better due to the AF sensor sensetivity even when stopped down

 

[briansquibb]

I don't understand why people seem to think that f2.8 is *always* better than f4 and above - in many situations, the dof of f2.8 larger apertures is just too thin, and the bokeh of f4 is ok too if there's no irritating object directly behind the dof pane. This is definitely true for my macro lens: 2.8 is just ridiculous if your object is not a flat piece of paper.

f2.8 and faster lenses focus faster and better due to the AF sensor sensetivity even when stopped down

I agree with that - most of my portrait shots (head only) are taken at f/5.6 or f/6.3 - which is why the 24-105 is more than adequate in good light and in fact more useful than a 24-70 on a 1.3 or ff. When prints up to A4/10x8 are the intended output media the IQ from the 24-105 is more than sufficient when stopped down.

Macro shots I tend to use F/11 as the default and for static objects I will focus stack using f/8

 

[D.Sim]

I don't understand why people seem to think that f2.8 is *always* better than f4 and above - in many situations, the dof of f2.8 larger apertures is just too thin, and the bokeh of f4 is ok too if there's no irritating object directly behind the dof pane. This is definitely true for my macro lens: 2.8 is just ridiculous if your object is not a flat piece of paper.

I would think the 2.8 on the Macro's is more to cater to the AF capabilities of the cameras - activate the higher sensitivity focus points for a more accurate shot - which would be even more important at Macro distances - you'd stop down to shoot, but for focusing you'd need that wide aperture?

That said - while IS does *somewhat* affect the quality of the IQ - a moving element will generally not be very kind to your shot - what will happen if you were to turn off the IS on the lens, THEN shoot handheld?

Taking for example the venerable 70-200 f2.8 L IS vs non IS

If the IS version were to be shot with IS turned OFF, at same shutter settings at a same object from a same distance, would the non-IS version show up sharper, as there is no moving IS element to get in the way?

If so, it will likely carry forward to the other lenses as well - likely, becuase AFAIK the lens designs will be different between the two versions, but it will give you a general idea when the two top of the class lenses go head to head, and of the two versions, one will turn out sharper... no?

 

[sanj]

Thank you all for taking time out to reply to my question.
I sort of understand, but so wish that the 24-70 II had IS in it... :-[
Regards