Diffraction Limited Aperture

[DigitalScape]

I came across this term (Diffraction Limited Aperture) and have been pondering its significance.  I came across the term  in Bryan Carnathan's review of the Canon 50D (http://www.the-digital-picture.com/Reviews/Canon-EOS-50D-Digital-SLR-Camera-Review.aspx).  The premise is that the sensor pixel pitch will set/determine the best aperture for image sharpness (not to be confused with DOF).  The equation Bryan is using is 1600/pixel pitch (mm).  The 1600 comes from the equation calculating the Circle of Confusion (Coc) - (http://en.wikipedia.org/wiki/Circle_of_confusion).  I have seen values of CoC ranging from 1500 to 1730, so I am guessing that Bryan's use of 1600 is middle ground.

So,for a Canon D40 (pixel pitch of 175 pixels/mm), the lens aperture for optimal sharpness is f/9-f/10 (depending on your CoC constant).  Using a smaller aperture will result in a deeper depth of focus, but not necessarily a sharper image.

How does this wrap around your mind?

[motleypixel]

I delights me John...these are good topics!  I really like f/8 myself most of the time if all I'm concerned with is sharpness.  I'll have to read those links though to make some sense of this.