[quote="petal666]Due to the 1.6x crop of the 10D it isn't an issue.[/quote]
Ok, yes of course. That makes perfect sense.
Also the 28 is a strange lens in that it is at it's shortest when at 70 and the front element extends when you go to 28mm. So really the problem is at 70mm and because of the crop all is good.
Although the crop takes care of the problem, even with the lens at its shortest at 70mm, I don't think that this will actually be the case.
The issue here will be the field of view of the lens, which, regardless of the
physical length of the lens, will be wider for a 28mm focal length than it will be for a 70mm focal length.
To prove this, just wrap a paper hood (or something similar) around the lens with the lens set at, for this example, 70mm.
Keeping the lens at 70mm, extend just this hood until you can
just see it impeding upon your feild of view in the viewfinder.
Now, without changing the relative position of this hood, move the lens to a wider setting. You should see a far greater intrusion of this hood with the wider angle than you do at the longer focal length setting.
Am I making any sense?