QTR-Quadtone RIP

Roy,

Eric Chan made a custom icc profile available in the Adobe Lightroom  
forum.  His profile is for converting from gamma 1.8 to 2.2 in  
Lightroom and was designed for printing to the ABW Epson driver.   
Strangely, using this profile, instead of the Create-icc custom  
profiles, seems to also work well when printing to QTR from  
Lightroom.  Here is the link to download Eric's profile and the Adobe  
Forum thread where this is discussed:
http://people.csail.mit.edu/ericchan/photos/tmp/GrayGamma22Print.zip
http://www.adobeforums.com/cgi-bin/webx?128@@.3bc43829
I think the rationale for doing this was that Epson ABW expects gamma  
2.2 input and in Lightroom everything is gamma 1.8 (ProPhotoRGB).   
However, I don't understand why this profile would improve printing  
to QTR.

Carl

> Sorry for jumping in late -- I've been away for the last week.
>
> I've been trying various things with LR and color management.  It's
> surprising that
> its so different in many ways from Photoshop -- you'd think they would
> capitalize
> on their PS experience.
>
> It appears that when you print with a custom profile in LR that the
> problem is not
> lack of ICC conversions but double profiling.  Profiles have two  
> sets of curves
> -- one for sending data to the print driver and the other for  
> displaying as in
> softproofing.  The reduction in dMax indicates to me that what is
> printed is similar
> to a proof print.  I.e if you setup softproofing and enable Ink Black
> Simulation you
> get the same effect.   You can also see this happening if you take  
> an image in
> PS, convert it to Gray Matte, and then convert it again to say GG2.2
> without BPC.
>
> So my guess at this point is that LR is setting up a conversion to  
> your custom
> print profile but that ColorSync later on is converting again -- (all
> this is before QTR
> ever sees anything).
>
> Input files also have some very interesting conversions happening  
> when you
> import.   It appears that embedded profiles are honored but everything
> is converted
> to a linear gamma profile they call "Melissa RGB".  But when you look
> at histograms
> or R G B percents everything is again converted to sRGB.  All this  
> makes it
> pretty mysterious when you try to figure out what to do.
>
> Printing targets for making ICCs is likely to be somewhere between  
> impossible
> and tricky to know what gets to the driver.
>
> I'd be curious if anyone has info about the profiles for color
> printing and the Epson
> driver.  I'd think it may be tricky to get identical results from both
> LR and PS.
>
> Roy
>
>
> On 6/30/07, Carl Schofield <list@...> wrote:
>> Walker,
>>
>> I think Roy will have to address that question, but I thought that
>> QTR was relying on Photoshop to handle the front end icc conversion.
>> I didn't realize that LR was passing the CM buck, but what you say
>> certainly helps explain the problem.
>>
>> Thanks,
>> Carl
>>
>> On Jun 30, 2007, at 5:57 PM, Walker Blackwell wrote:
>>
>>> I believe I just got to the bottom of it. Photoshop (it seems) does
>>> all of the grunt-work when it comes to pure color management. That's
>>> because it's been around since before OSs had any color management.
>>> So when you print a big'ol image it's actually doing a hard-
>>> conversion of that file to the out-put profile and then sending that
>>> data along to the print driver. (Thus all the time it takes to
>>> print.) All the print driver has to do is send the data to the
>>> Printer.
>>>
>>> Lightroom, on the other hand, tags the image with the profile and
>>> lets the print driver handle the conversion. I think that is where
>>> it's getting sticky. This explains why I was having such a hard time
>>> with the old Spro9600 drivers when printing color. They just  
>>> couldn't
>>> handle the profile conversion themselves. The driver expected a
>>> converted file.]
>>>
>>> It also explains the slight lag between finishing a file rip in
>>> Lightroom and seeing it come up in the print queue.
>>>
>>> Can QTR handle ICC profile conversions? And is it v4 compliant? Most
>>> likely more and more applications will come out soon that will
>>> require OS and Driver color management instead of doing all the work
>>> themselves. It makes everything faster and more scaleable.
>>>
>>> The nice thing is the Adobe CMM is open source and available to use
>>> for such a thing as driver-based ICC conversions.
>>>
>>> take care, Walker
>>