Lab Tiffs and Qimage

Ernst Dinkla

Sr. Member

Posts: 410

Lab Tiffs and Qimage

« on: July 15, 2010, 10:04:15 AM »

Is it possible that Qimage in the past, version 266, could handle Tiffs in Lab color mode (giving the right color) and no longer in version 290 (excessive yellow cast from paper white upwards)? Or was it never able to handle Lab modes and did I replace that Lab mode Tiff with an RGB converted version then? My memory lacks and the recalled job doesn't give the information. I recalled that job and I get the same yellow, in normal display + softproof on the screen and in print but of course a Tiff with the same name in RGB mode wouldn't cause the effect.

The thumbnail doesn't show the yellow cast.

It is not so that I need that Lab mode very much but I'm just curious whether it is my memory or Qimage.

Edit: The 102a beta version that I installed on XP to check it doesn't show that yellow cast in Full screen display, examinator and softproof (no print made) , the 290 on Vista (64) shows the yellow cast as described in everything but the thumbnail.

met vriendelijke groeten, Ernst Dinkla

spectral plots of +100 inkjet papers:
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm


« Last Edit: July 15, 2010, 10:18:10 AM by Ernst Dinkla »	Logged

Fred A

Forum Superhero

Posts: 5644

Re: Lab Tiffs and Qimage

« Reply #1 on: July 15, 2010, 11:30:09 AM »

Ernst,
I sent you a private email with 266 attached.
See if you can find the same monitor profile you used when you get normal thumbs, and use it (rebuild) in the one with yellow thumbs.
Hope something helps

Fred


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rayw

Sr. Member

Posts: 440

Re: Lab Tiffs and Qimage

« Reply #2 on: July 15, 2010, 11:33:20 AM »

Hi Ernst,

Thumbnails may be always OK, since possibly uses the jpeg embedded in the Tiff, if there is one.

Best wishes,

Ray


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Ernst Dinkla

Sr. Member

Posts: 410

Re: Lab Tiffs and Qimage

« Reply #3 on: July 15, 2010, 12:41:14 PM »

Quote from: rayw on July 15, 2010, 11:33:20 AM

Hi Ernst,

Thumbnails may be always OK, since possibly uses the jpeg embedded in the Tiff, if there is one.

Best wishes,

Ray

The preview print page is alright so that must build om the same embedded jpeg if that is how it works. The HQ print preview version gets the yellow cast again.

It is Atkinson's Lab Test Page tiff that I used. The translation to RGB sRGB or to another color space in Photoshop gives a better image than both versions of Qimage do on the fly. Could be that the old version of Qimage (without the yellow cast) uses an absolute colormetric rendering when the Lab mode is translated to RGB + a profile or a gamma issue like a conversion to say ProPhoto on the fly while the image gets sRGB assigned as it can not have a profile assigned in Lab mode. Image is much heavier than the Photoshop one. I could find a match in the older versions but it is more broken in 290 so I leave it like that. Wonder if anyone ever uses it and if not make that Lab mode unavailable I would suggest.

Fred, thank you for that file. As the 102 beta showed that it can work (more or less) I don't think I have to try 266 again.
The monitor profile isn't the problem.

Edit: I see the same yellow cast happen on the conversion when I switch to the ICM color engine in Photoshop, Have to see what other conditions there are:
Absolute Colormetric is another condition. So Qimage uses that too on the fly, on the conversion.
The other condition is a conversion to sRGB or AdobeRGB, it doesn't happen with Colormatch or ProPhoto. I guess a gamma issue then, the first two are 2.2 the last 1.8.
PS CS2 on Vista 64.

In Qimage it is all weirder. With CM off it still does that. The profile assigning or EXIF reading switched off doesn't have an influence. LCMS at work here?

met vriendelijke groeten, Ernst Dinkla

spectral plots of +100 inkjet papers:
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm


« Last Edit: July 15, 2010, 01:26:49 PM by Ernst Dinkla »	Logged

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