View Full Version : optical vs chemical focus
Jan_6568
4-Dec-2006, 10:59
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
4-Dec-2006, 11:04
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
4-Dec-2006, 12:34
Thank you very much for making it clear to me.
regards,
Jan
Leonard Evens
4-Dec-2006, 14:02
The human eye is most sensitive at about 550 nm, which is in the yellow green part of the spectrum.
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