IS or VR with respect to sharpness

[markd61]

The question I am asking is whether there is documentation or anecdotal evidence that IS affects image sharpness when switched off and the lens is on a tripod.

I ask this because I have a several IS Canon lenses and have noted that when I shoot on a tripod with the IS switched off and the exposure is longer (1/15 or more) I can detect some softness in the images. This does not happen with my non-IS lenses. Also, I notice that when I use flash in studio or in the  field my images are demonstrably sharper. I am wondering if this is due to the IS elements shaking on their mount as a consequence of mirror slap ( I guess I need to try some more tests).

Also, I noted that Canon did not offer IS on their new 24-70 2.8 L II and it is noted for its exceptional sharpness. Could this decision on their part be because of optical compromises necessitated by an IS design? I do note that Tamron does have VC on their lens and while it is well regarded most everyone agrees that it falls short of the Canon.

[Hans Kruse]

The question I am asking is whether there is documentation or anecdotal evidence that IS affects image sharpness when switched off and the lens is on a tripod.

I ask this because I have a several IS Canon lenses and have noted that when I shoot on a tripod with the IS switched off and the exposure is longer (1/15 or more) I can detect some softness in the images. This does not happen with my non-IS lenses. Also, I notice that when I use flash in studio or in the  field my images are demonstrably sharper. I am wondering if this is due to the IS elements shaking on their mount as a consequence of mirror slap ( I guess I need to try some more tests).

Also, I noted that Canon did not offer IS on their new 24-70 2.8 L II and it is noted for its exceptional sharpness. Could this decision on their part be because of optical compromises necessitated by an IS design? I do note that Tamron does have VC on their lens and while it is well regarded most everyone agrees that it falls short of the Canon.

You mentioned IS elements and mirror slap and exposures longer than 1/15s. If you have softness in this case it is due to the mirror slap. Shoot in live view instead to avoid mirror slap and the use of EFCS. The Canon IS system except very old ones are designed to recognize being on a tripod and therefore inactivate the IS system, but I believe it is best to still switch the IS off when on a tripod so that the IS does not kick in unwanted. The Canon 70-200 f/2.8L IS II is an exceptionally sharp lens and with IS turned off on longer shutterspeeds on a stable tripod and shot in live view the sharpness is exceptional.