ZK Sonnar and Optical Anti-Aliasing

[Sonnar Brian]

Some fast math in this thread:
http://www.rangefinderforum.com/forums/showthread.php?t=84953

and I speculated that the Jupiter-3, and Zeiss Sonnar that it was derived from, was a perfect match for the Leica M8's Bayer Pattern Mosaic filter. Basically, the Bayer site is a 2x2 grid of 6.8micron sensor elements.

And another reason to take some pictures of grass in the Sun.

1949 ZK Sonnar, original German parts.

At F1.5 the spec is 30LP/mm

100% crop:

at F4 resolution improves:

100% crop:

Color aliasing is creeping in. Note "color Sparkles" on some of the pixels.

What lesson can be learned from this?

Well, for one I like shooting pictures of grass in the Sun to test lenses.

Also opening the aperture up on a lens is a quick and dirty AA filter.

 

[Y.B.hudson III]

I like the J 3 at f/1.8~f/2.0 (increased contrast and sharpness)...at f/4 I start getting a color shift towards blue, indicating diffraction raising it's little head...maybe?

 

[Sonnar Brian]

Diffraction is not the cause of the color shift, it is the increase in contrast and resolution.

Diffraction creeps in at about a 3mm opening (from memory), which is F16 on the Jupiter-3.