"Wayne J. Cosshall" wrote:
David Ruether wrote:

Interesting images (I am curious why you chose such wide
stops with high shutter speeds, though...).

I used a wide aperture on those images because the info sheet that came
back with the camera suggested a wider aperture would produce the sharpest
result because of diffraction effects as the aperture got smaller.

Maybe. IR wavelengths are longer, and diffraction might bite you sooner (as
you stop down).

To test this I went out and shot with a Canon 50mm f1.8 and a Canon 100mm
f2.8 macro at the full range of apertures to determine with apertures gave
the sharpest results:
http://www.dimagemaker.com/article.php?articleID=790

Good test. Thanks for putting it up. Both f/5.6 and f/8 look pretty good to
me for both lenses. Even f/11 seems usable.

Are you using the IR focusing marks on your lenses? Interestingly, most of
the lenses here do have IR focusing marks. (All of the 17-40, 24TSE, 50/1.4
and 100/2.0 have an IR focusing indicator.)

David J. Littleboy
Tokyo, Japan