This one's for the pixel-pokers. Pentax vs Canon L! What's going on here?

[Village Idiot]

So, what is sharper...

EF 70-200mm F/2.8 at F/4
or EF 70-200mm F/4 at F/4

lol

What cameras? An XTI on the 70-200 f/4 at f/4 would probably be sharper than a 5D with the 70-200 f/2.8 at f/4.

 

[prodigy2k7]

What cameras? An XTI on the 70-200 f/4 at f/4 would probably be sharper than a 5D with the 70-200 f/2.8 at f/4.

I meant lens wise..
70-200 F/4 at F/4 on XTi
70-200 F/2.8 at F/4 on XTi
or
70-200 F/4 at F/4 on 5D
70-200 F/2.8 at F/4 on 5D

Same body, almost same lens...what is sharper?

Edit: Wait what? Even on a 5D XTI with F/4 would be sharper? Is there a noticable difference or do you need to crop to 100% to see it?

Shoot, if there is a noticable difference ill probably get both eventually... I really want to shoot indoors but if I know im going to be outdoors ill get the F/4 non IS for fun...

 

[Village Idiot]

The XTI has a crop sensor and uses a smaller portion of the lens. The sharpest part of the lens is the center. That's why stepping down the aperture makes the photo sharper.

 

[prodigy2k7]

oh ya, forgot about crop factor...
Well I have the XTi, which is sharper 2.8 at 4 or 4 at 4

I thought 2.8 would be since its being stopped down, but since the 4 has fewer elements like you said....i dunno