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Re: [OM] B&W filters on digital [was Non Bokeh 50mm F1.4 pictures]

Subject: Re: [OM] B&W filters on digital [was Non Bokeh 50mm F1.4 pictures]
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Fri, 04 Jun 2010 11:43:31 -0400
CH was complaining about his 5D Mk II, not his original 5D.  Moose and I 
are still with the 5D.  I did not see the noise that CH and Moose say 
they can see.  At 100% magnification I see pixelization in CH's image 
which ACR's noise control can eliminate.  Whether the pixelization is 
dispensed with or not I see posterization (but not noise) after reducing 
the size to about 50% or less and after turning off every color except 
pure red in ACR's B&W converter.  If I have only pure red available in a 
JPEG image I have (at most) 256 shades of gray.  That to me is the 
probable source of the posterization although there are never more than 
256 shades of gray in a B&W JPEG.  Perhaps the Bayer pattern is a 
problem if all the blue and green pixels are totally eliminated?  If I 
return blue to the halfway point the posterization goes away.

Actually, after mentioning "half way point" I realized that perhaps I'm 
the problem.  The half way point is zero.  In turning the red channel to 
+100% and everything else to -100% perhaps I've boosted half of the red 
pixels to the point of being blown out.  I've never much paid attention 
to what the scales on those sliders actually mean.  Just push them 
around until I get something I like.

Chuck Norcutt


Ken Norton wrote:
> I don't understand something. How can we have three 5D owners not
> agree about noise patterns in their cameras?
> 
> AG
> 
> 
> 
> 
> 
-- 
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