Digital BW, The Print

> ... The advantage of only using the 'sweet spot' 
> area of the lens is clear, ...

I think this is a bogus argument that is used mostly as a way to sell
obsolete lenses to digital camera owners.  For a given price point and all
else being equal, the larger the image circle, the poorer the lens will be.
One doesn't get something for nothing.  Covering more area requires more of
an optical design, not to mention heavier, larger lenses.

Likewise, the need in the full-frame cameras to keep the rear element away
from the mirror requires a greater sensor to lens space than the smaller
digital sensors require.  This is significant for wide angle lenses.  One
reason many prefer rangefinder cameras is that their symmetrical-design wide
angle lenses are better than the retro-focus SLR lenses.  True, with digital
we may be stuck with retro-focus due to the problem of more light fall-off
caused by the sensors when the light angle gets too low, but the old
full-frame clearance distance is probably way more than optimal when one is
balancing all the factors that must be considered in the design.

For example, I'm a big fan of the Canon tilt and shift lenses, but that big
image circle and radical retro-focus design makes the 24 and even 45mm TS
lenses weaklings when it comes to resolution, etc.  My 45 TS is an expensive
lens, and it's the poorest lens I've used on the Rebel -- visibly inferior.

Paul
www.PaulRoark.com