QTR-Quadtone RIP

Roy Harrington wrote:
> On Wednesday, September 6, 2006, at 03:25  PM, Ernst Dinkla wrote:
> 
>> Roy Harrington wrote:
>>
>>> The only way to understand all this is break everything into 
>>> individual
>>> steps and
>>> understanding what each does.
>> Roy,
>>
>> One way to get some grip on this is by getting the knowledge
>> how QTR does the RGB to Grayscale conversion.
> 
> Well, that's easy.   For a gray RGB file i.e. R=G=B, the grayscale 
> values are the same as R, G, or B.
> When it's actually a color image fixed weightings are used:
> 
>      Gray = .31*R + .61*G + .08*B
> 
>> Given the print results I get it must be compatible to Qimage
> 
> Qimage never does RGB to Grayscale, but Grayscale to RGB in the absence 
> of profiles & CM (Ptr ICC Off)
> I think it does R=G=B = Gray,  so I guess that's compatible.   In 
> general these probably would be
> the non-CM conversions for any non-ICC product.
> 
> All CM conversions will preserve L values as much as possible.  The 
> difficulties are where K=100 is not L=0,
> then BPC etc can give various results.
> 
> Roy

Roy,

So the main lesson learned is: avoid Photoshop to check Print 
to File results, even with CM off. The other one: there's no 
flaw in the Qimage transfer when CM in Qimage is off.

Ernst

-- 

                    --
           Ernst Dinkla


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