So, why no IS?
- If you are interested in a fast lens - f/2.8, than you are most likely shooting in low light. Otherwise, you would purchase the 24-105 f/4 IS.
- If you hand-hold, then you need to bump up the shutter speed to compensate, and thereby negate some of the "low light" advantage of the fast aperture.
- This is not a sports lens due to the focal length, (for the most par) - where IS isn't really needed.
- The focal range is in the general purpose/walk-around range.
So, a general purpose, low light lens, not for sports, and used with a tripod?
Without IS, this becomes a very expensive, really sharp, general purpose lens - but not a low-light lens.
Am I missing something?
It depends what your taking pics of I spose, the shutter speed to stop most movement will generally be faster than the shutter speed to prevent camera shake so IS wouldnt improve its low light ability for such subjects.
For landscapes I'd guess Canon's feeling is that less serious users will probabley go with the 24-105 IS while more serious ones will be happy to use a tripod when needed to really exploit the sharpness to the full.
Compaired to the 17-55 the 24-70 isnt as long when you take the crop into account which cuts down the need for IS a bit and its also a good deal heavier/longer. Maybe not so much of a problem on a 1D but this new version looks like it will balance much better on a 5D to me with both being around the same weight.