inconsistent focus with 70-200 2.8L mkI

[QUOTE=tompfeiffer;148​46983]

TSchrief wrote in post #14843198
Please back up that statement. According to this web-site: http://www.dofmaster.c​om/dofjs.html DOF with a crop sensor is as follows:
f/2.8, 10', 70mm - DOF = 8 inches.
f/2.8, 10', 200mm - DOF = less than 1 inch. (Edit on this line, 200 not 2000 as originally mis-typed)

http://2.bp.blogspot.c​om …KCuWf04MxG0/s16​00/DOF.jpg

But that's actually for a 50mm lens, at 70mm f/2.8 it's only about a foot, but still not .25". See here:
http://www.johnhendry.​com/gadget/dof.php

Sorry for the confusion.

I went to the johnhendry.com website and entered the numbers. That web-site seems to agree with the one I quoted above. It gives the following data, focused at 10 feet:
f/2.8, 70mm - DOF = 8 inches
f/2.8, 200mm - DOF = 1 inch
Where are you finding 10 inches DOF with a 200mm lens at f/2.8? You can't even get 10 inches DOF at 10' and f/2.8 with the 70mm lens. Neither of the sites in this post say what you are claiming they say. May I suggest setting up a simple test shot in your home? See my wine bottle shot above. Or, prove it to yourself.

I have included .pdf of the johnhendry site's results for everyone's convenience.

yes. no. yes. yes. and most definitely (6" of concrete)...

7D. i ran through every full stop. yes. yes. i understand those are SLLOooooow shutter speeds. never heard the TWICE the focal length but at least the SAME AS the focal length...

i took one shot at each of the full steps (2.8, 4.0, 5.6, 8.0, 11.0, 16.0, 22.0, 32.0) but only posted the sampling...

ill look into a better 'test'. in the f32 shot the brickwork looks fuzzy to me and i would think it would have more than 6" dof...

thanks for the insights

Ltdave wrote in post #14848295
ill look into a better 'test'. in the f32 shot the brickwork looks fuzzy to me and i would think it would have more than 6" dof...

My guess as to why the f32 shot looks fuzzy (the whole thing looks fuzzy to me, not just the bricks), is diffraction.

If your tripod head is not so great, the mirror slap will cause enough vibration to blur your pictures. Try with mirror up. At least to eliminate this factor. And perhaps the f32 adds to the blur.