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ACV Curves from ChartThrob

ACV Curves from ChartThrob

2015-01-21 by grimmieoldfart@...

Can anyone or would anyone be willing to educate an old fool on how to create a profile curve with an Photoshop curve (acv) in it?

I am checking/playing with ChartThrob but can not seem to get QTR to accept the acv reference - same old fault - "Curve Specified but no valid data on line 41...".

I can not figure out how to crack this nut. I have tried everything - ChartThrob requires RGB mode to complete. I save the curve & falling Roy's advice, close the file, creat a grayscale file, load the curve, & save it as a Gray Curve under a different name.

Nothing seems to work... At least it is a consistent result.

TIA,
Phil


Re: ACV Curves from ChartThrob

2015-01-21 by richard@...

I'm assuming this is for making digital negatives. Are you working on a Mac or a PC, and what printer model?

In most cases this error has to do with the file path either changing after it was embedded with the .acv curve or something bad in the file name of the .acv curve. With the file name/folders for the .acv files "spaces" are ok but "/" or "\" are not. The .acv files don't have the same kinds of problems with illegal file names in the qdif/.txt files. I am not sure if there is a character limit for the acv file name, but I might make sure that its name isn't too long.

Are you dragging the .acv file from a file system browser to the "GRAY_CURVE= " line or typing the file path manually?

Richard Boutwell

Re: ACV Curves from ChartThrob

2015-01-23 by sanking@...

Phil,

Try QTR Build Script by David Eisenlord. You can download a folder, which contains the script, a 21 step wedge, and instructions, from his web site. http://www.davideisenlord.com/?p=229

After you build the curve you read input/output values in PS with Curves, and then just insert these numbers directly into the QTR profile with the GRAY_CURVE command, for example.


GRAY_CURVE="0;0 7;10 13;20 20;30 28;40 37;50 43;55 49;60 57;65 65;70 73;75 80;81 86;86 93;92 95;95 100;100"


Sandy

Re: [QuadtoneRIP] ACV Curves from ChartThrob

2015-01-24 by Jacques Caron

Hi

Is it a good way to work if I use standard paper instead of negative media (I won't reverse the greyscale).
And if so, my paper has some sort of pattern (Epson Cold Press); do I have to blur it in Photoshop before reading it?

Thanks

Le 2015-01-23 à 10:06, sanking@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> a écrit :



Phil,

Try QTR Build Script by David Eisenlord. You can download a folder, which contains the script, a 21 step wedge, and instructions, from his web site. http://www.davideisenlord.com/?p=229

After you build the curve you read input/output values in PS with Curves, and then just insert these numbers directly into the QTR profile with the GRAY_CURVE command, for example.


GRAY_CURVE="0;0 7;10 13;20 20;30 28;40 37;50 43;55 49;60 57;65 65;70 73;75 80;81 86;86 93;92 95;95 100;100"


Sandy


Jacques Caron

Re: [QuadtoneRIP] ACV Curves from ChartThrob

2015-01-24 by sanking@...

Is it a good way to work if I use standard paper instead of negative media (I won't reverse the greyscale).
And if so, my paper has some sort of pattern (Epson Cold Press); do I have to blur it in Photoshop before reading it?

The QTR Build Curve script can also be used to build a correction curve for a positive print. For a standard positive print just print the 21 step wedge and scan the print and derive the .acv curve. In this application you would not invert the step wedge file.

Slight blurring might help with some papers, or with digital negatives to smooth out process artifacts.


Sandy

Re: [QuadtoneRIP] ACV Curves from ChartThrob

2015-01-24 by Jacques Caron

Thanks Sandy

I'm working on it!

Jacques

Le 2015-01-24 à 09:37, "sanking@... [QuadtoneRIP]" <QuadtoneRIP@yahoogroups.com> a écrit :



Is it a good way to work if I use standard paper instead of negative media (I won't reverse the greyscale).
And if so, my paper has some sort of pattern (Epson Cold Press); do I have to blur it in Photoshop before reading it?

The QTR Build Curve script can also be used to build a correction curve for a positive print. For a standard positive print just print the 21 step wedge and scan the print and derive the .acv curve. In this application you would not invert the step wedge file.

Slight blurring might help with some papers, or with digital negatives to smooth out process artifacts.


Sandy



Jacques Caron

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