optical vs chemical focus

[Jan_6568]

Could someone explan what exactly is "chemical focus". I do use bellows extension to correct for chemical focus difference but I would like to understand the theory behind.

regards,

Jan

[Dan Fromm]

Could someone explan what exactly is "chemical focus". I do use bellows extension to correct for chemical focus difference but I would like to understand the theory behind.

regards,

JanIIRC, human visual acuity is best in the yellow part of the spectrum. Orthochromatic films are most sensitive to blue/uv. When the lens isn't very well corrected for chromatic aberration, the blue/uv will focus to a slightly different plane than the yellow. Not so much of a problem with modern films and lenses.

[Jan_6568]

Thank you very much for making it clear to me.

regards,

Jan

[Leonard Evens]

The human eye is most sensitive at about 550 nm, which is in the yellow green part of the spectrum.