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tweak quad file, high tones a bit too hot

tweak quad file, high tones a bit too hot

2014-09-28 by paulmwhiting@...

I took a (color) digital photo and after converting it to b/w, I printed it out, and it was fine on the monitor. But in the print my highlights are not blown out by any means, just a bit "hot". Am using EB6 inkset on an Epson 1400 and the QTR quad file for that inkset.

Is there a tweak in its QTR qidf I can alter to tone that down without having to re-linearize? A bit lazy, I know. I know how to tweak the qidf file, it's in simple text format - maybe lower the LIMIT_Y=70? or GRAY_VAL_6=11? or?

Thanks all,

Paul


Re: tweak quad file, high tones a bit too hot

2014-09-29 by richard@...

So the problem is that there is tone on the screen but it is printing too dark, and you are trying to get tone/density back into the highlights in the print by altering the qtr profile?

The Short answer is: no, you cannot alter the .qdif text file without needing to relinearize. The simplest thing is to just alter the image to match what you want to print.

The long answer is: Lowering the ink limit will make that shade lighter, and lowering the grey value will make it intersect the next darker ink at a different point. Doing that will unpredictably change the shape of the overall greyscale, but it will not really have much of an effect on the overall density. The main point is that anytime you touch the ink limits and/or grey values you will need to relinearize your curve—there is no getting around that. This is one case of being a little lazy (and reckless) with the ink limits could introduce a whole lot of other problems down the road, and maybe ruin what was possible a good/functional profile. This is why people have problems linearizing their curves when creating their own profiles and then can't easily track down what exactly is causing it. If you don't have the correct grey values (or just calculate inaccurate cross over points) then you will have more trouble later in the process.

I would suggest that you use the eye dropper tool and the info pallet in photoshop to see exactly what grey values are blowing out in the highlights. Then print a 51 step tablet included with QTR (with the same paper and profile or just include it as a layer in the print in question). Then you will see if that same value is also blowing out or printing too hot on the step wedge as well. If there is no obvious problem with the step wedge then just use that as a guide/target tone for adjusting the image for print in photoshop. If the stepwedge looks different than your display then maybe your display has the wrong luminance/gamma/white point for the print viewing environment.

I tend to keep a printed stepwedge with that paper and profile right by the workstation to see if my 3-5%k will print as light/dark as it is perceived on the screen.
Richard Boutwell

Re: tweak quad file, high tones a bit too hot

2014-09-29 by paulmwhiting@...

Thanks Richard, I've been trying to follow your suggestions.

I printed out the 51-step file and compared it to my photo, and actually I don't have any blown out areas... it's just that I'm trying to get more texture in the highlights. Perhaps I didn't explain that sufficiently, sorry. The brightest patch on my photo is about 242 pixels and that seems to correspond to about 6 or 8 % on the 51 step file.

I'll work on that area in PhotoShop, as you suggest, and not alter the profile.

A couple of months ago a member (perhaps you?!) here was working on a manual for QTR beginners and said he would concentrate on the linearization part of the process - that seemed to be the area where most people had difficulty.

Another member here gave me some great help off-group, using a 20 step Kodak strip as a reference, then comparing those RGB values with the actual RGB values on a print of that file using my paper and my inkset. Then we interpolated between the files and entered the actual (not the Kodak scale's) Density values in the 21 empty boxes at the final step of creating the profile.

Nevertheless, a detailed manual would be quite welcome. And I thank you for your help as well.

Regards,

Paul

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