[argyllcms] Re: Generated camera profile too bright

  • From: Chris Lilley <chris@xxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 3 Apr 2012 17:17:38 +0200

On Tuesday, April 3, 2012, 6:06:21 AM, Graeme wrote:

GG> Andreas F.X. Siegert wrote:
>> I think I got fooled by the exposure because of the background.
>> But even if I push the exposure before generating the linear tiff I get
>> the overexposed patches.

GG> Hmm. Looking at the .tif, white is at around 16%. So the resulting profile
GG> will boost everything by a factor of about 600% - which is exactly
GG> what it's done. Is this really what you intend ?

GG> (Normally you would want to expose the image so white is near 100%.)

Looking at the NEF (raw) file in Nikon Capture NX2 at default settings, I am 
seeing the black patch at rgb 27, 27, 28 and the white at rgb 223, 225, 224. 
(The working RGB space is Beta RGB). So the exposure seems reasonable to me; it 
is the conversion to linear TIFF that is causing the big drop in lightness.

I notice that the patches show considerable surface texture (the samples above 
used a 5x5 sample area to try and overcome this). A little defocussing might 
help here.

 Chris Lilley   Technical Director, Interaction Domain                 
 W3C Graphics Activity Lead, Fonts Activity Lead
 Co-Chair, W3C Hypertext CG
 Member, CSS, WebFonts, SVG Working Groups

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