Lens Contrast Characteristics?

[realeyz]

What is it about a particular lens that makes it more or less contrasty? From a rudimentary scientific standpoint this doesn't make any sense to me. I mean if the optical quality of a set of glass elements was to somehow let through more or less light then of course this would be similar to closing down or opening up your aperture, but how can there be characteristics in glass that yield differences in contrast? The only way I see that this could be possible is for the transmission characteristics of the lens to be different for very bright light sources vs. very low or dark light sources.

What am I missing?

 

[Iliah]

Lens contrast is not the same as contrast on print. Lens contrast has much more to do with lens resolution. Lens contrast is a "measure" of how lens resolve differences in subtle tonal variations (deficiency of lens contrast, or "microcontrast", or "clarity" we counteract in PS with USM 30/15/0 or even more). Lens with poor contrast produce "foggy" images.

 

[realeyz]

Can you point me to some references for this?

 

[Iliah]

It's more or less explained in how-to's on reading MTF charts. Normally we evaluate resolution at 60 lpm, and lens contrast at 20 lpm.

Actually, 5 lpm is also very important, because lens contrast is important not only in small details, but in larger structures as well.

I found some stuff here:
http://www.nikonlinks.com/~nicke/photo/lenstest/photodo/mtf.html

Solid line on the "resolution and contrast" graph is actually pretty typical for some German lenses

PS. Speaking of German lenses:
http://www.photozone.de/3Technology/mtf.htm

 

[Gale]

Todd,

Your thinking facinates me.

Iliah, always knows the answers.

Iliah, your a true mathematical genious.

To think math and science were my interests while growing up.
Wonder what happened. Now I wonder if 2+2 still equals 4.

Well I may not totally understand the higher mathematical explanations, I at least get the drift.

Regards
Gale