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Less lens contrast to cope with narrow DR of camera?



 
 
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  #1  
Old September 20th 07, 01:29 PM posted to rec.photo.digital.slr-systems
RichA
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Posts: 2,544
Default Less lens contrast to cope with narrow DR of camera?

So since less contrast "sometimes" means less sharpness, you end up
putting up with softer images?

http://forums.dpreview.com/forums/re...hread=24340033

  #2  
Old September 25th 07, 12:48 AM posted to rec.photo.digital.slr-systems
John Sheehy
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Posts: 878
Default Less lens contrast to cope with narrow DR of camera?

RichA wrote in news:[email protected]
22g2000hsm.googlegroups.com:

http://forums.dpreview.com/forums/re...hread=24340033


Reducing contrast in the optics is like under-exposing, only with more
noise in the shadows, once you have re-normalized the tones.

Basically, what is happening is that some of the light is not forming a
sharp image on the focal plane, but is scattering randomly. This means
that black becomes brighter, and even colored. That means more shot noise
for the lower tonal ranges than if you had used a high-contrast lens, even
if you under-exposed a bit.

The apparent increase in exposure latitude is an illusion. Under-exposing
with a high-contrast lens in such a way as to give the same exposure as the
low-contrast image minus the false "black" leaves less noise in the
shadows, and leaves more room for highlights.

--


John P Sheehy

  #3  
Old September 25th 07, 01:18 AM posted to rec.photo.digital.slr-systems
Paul Furman
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Default Less lens contrast to cope with narrow DR of camera?

John Sheehy wrote:

RichA wrote in news:[email protected]
22g2000hsm.googlegroups.com:


http://forums.dpreview.com/forums/re...hread=24340033



Reducing contrast in the optics is like under-exposing, only with more
noise in the shadows, once you have re-normalized the tones.


You might not want to re-normalize the tones though. And supposedly
there are some lenses which aren't as contrasty but are still sharp.
Flare reduces contrast in the way you describe and is rarely desirable
but if this was desirable for high contrast scenes, it probably would be
easy to make a flare filter or contrast reducing filter like how a
polarizer increases contrast. Otherwise you'd want whole other set of
lenses for high contrast shooting.

Basically, what is happening is that some of the light is not forming a
sharp image on the focal plane, but is scattering randomly. This means
that black becomes brighter, and even colored. That means more shot noise
for the lower tonal ranges


I'm not sure why there would be more noise... because the flare *is*
noise? If the shadows are brighter, there should be less noise. If you
try to increase contrast in the mid-highlights, that does increase noise
and looks awful trying to re-contrast a flared out shot but if you leave
the contrast alone, it might look just fine. Noise comes from recording
the signal too dark and trying to lighten it in post processing but if
you don't raise anything, just darken the shadows, it should be OK, right?

than if you had used a high-contrast lens, even
if you under-exposed a bit.

The apparent increase in exposure latitude is an illusion. Under-exposing
with a high-contrast lens in such a way as to give the same exposure as the
low-contrast image minus the false "black" leaves less noise in the
shadows, and leaves more room for highlights.



--
Paul Furman Photography
http://edgehill.net
Bay Natives Nursery
http://www.baynatives.com
 




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