09-25-2011, 11:23 AM
(This post was last modified: 09-25-2011, 11:24 AM by Brightcolours.)
[quote name='wim' timestamp='1316948667' post='11832']
512 nanometers, which is the generally accepted and used wavelenght for diffraction determination for general purpose photographic lenses. All this at the Rayleigh criterions of 9 % contrast, which according to the definition is the point where lenses can still make out a difference.
Kind regards, Wim
[/quote]
Where d\from do you get that 512 nanometers is used to determine diffraction for general lenses? It sits at the very end of the visible spectrum, basically... very short wave length (blue). Green already diffracts sooner, let alone yellow and red.
e-line (a green, 546.2 nm) was used originally for the early semiconductor production. They used such very narrow bands exactly for the purpose that longer wave lengths of a normal light spectrum diffract a lot sooner, not being able to reach such high resolutions as needed. So I have to doubt that 512nm is used to determine diffraction for normal photographic purposes...
e-line has a resolution limit of 374 lpmm at f4.
A more normal light spectrum has a way lower resolution at f4.
Maybe 512 nm gets used to compare lenses in certain technical applications, but it can not have any significance for normal photography with a light spectrum instead of a monochromatic blue light source... <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/unsure.gif' class='bbc_emoticon' alt=':unsure:' />
512 nanometers, which is the generally accepted and used wavelenght for diffraction determination for general purpose photographic lenses. All this at the Rayleigh criterions of 9 % contrast, which according to the definition is the point where lenses can still make out a difference.
Kind regards, Wim
[/quote]
Where d\from do you get that 512 nanometers is used to determine diffraction for general lenses? It sits at the very end of the visible spectrum, basically... very short wave length (blue). Green already diffracts sooner, let alone yellow and red.
e-line (a green, 546.2 nm) was used originally for the early semiconductor production. They used such very narrow bands exactly for the purpose that longer wave lengths of a normal light spectrum diffract a lot sooner, not being able to reach such high resolutions as needed. So I have to doubt that 512nm is used to determine diffraction for normal photographic purposes...
e-line has a resolution limit of 374 lpmm at f4.
A more normal light spectrum has a way lower resolution at f4.
Maybe 512 nm gets used to compare lenses in certain technical applications, but it can not have any significance for normal photography with a light spectrum instead of a monochromatic blue light source... <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/unsure.gif' class='bbc_emoticon' alt=':unsure:' />