Datacolor User to User Support Group.

All good observations. But color on the screen has fewer properties  
than color in the real world; a measured Lab value must be simplified  
into an RGB value... So the comparison is between two different  
conditions.

C. D. Tobie
Global Product Technology Mngr.
Digital Imaging & Home Theater
Datacolor.com
CDTobie@...

On Aug 14, 2009, at 11:33 PM, "dsainsbu" <david.sainsbury@... 
 > wrote:

> This is very similar to my experience.
> Clearly there is some point at which science gives way to art.
> I am assuming that the hue representation is accurate and all we are  
> looking at is tonal range (If that means grading from light to dark)
>
> David T is right about blacks. I have included a picture of the  
> excellent spydercube under my album "color cast".
> The black trap drops away to 0,0,0 and the specular highlight is  
> 255,255,255.
> The virtual gretag card's black of 50,50,50 is very weak by  
> comparison.
> where possible a color rgb value of the image in the computer would  
> be the same as the value measured by the spectro when printed on the  
> paper.
> On reflection this may not be the case, with deliberate distortions  
> introduced to "take advantage" of the sensitivities of the paper/ink  
> combinations at different parts of the tonal range. (To bring out  
> detail in that range)
>
> And I presume these distortions change with rendering intent!
>
> Dave Sainsbury
>
>
>
>
>
>> David,
>> I spent quite a bit of time with SpyderProof and my base  
>> measurement file and incrementally tweaked and built profiles that  
>> I then Spyderproofed until it looked pretty good.  Increasing the  
>> Brightness to +4 gave the best view in SpyderProof.  But when I  
>> printed out one of the "Matrix" images (the little girl with the  
>> flowers) I had used to tweak the profile, it was still too dark.  I  
>> increased the Brightness to +10 and printed and it looked pretty  
>> good.  The contrast seems a bit lacking.  I tried playing with the  
>> Contrast amount when tweaking the profile but didn't like the  
>> effect it had on light to dark transitions.
>> I tried, as you suggested, printing a "Matrix" image both from  
>> SpyderProof and from CS4 with the new profile and they both  
>> appeared to be the same.  So I am printing via CS4 OK apparently.
>> So, other than the contrast issue I think I have created a better  
>> profile than the one that Epson provided.
>> I am going to try the 729 patch target next to see if that improves  
>> it a bit more.
>> Thanks for your help.
>> Rick
>>
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