Making a multigrade calibration table for color head

ic-racer · Aug 26, 2023

john_s said:
Decade or two ago I found a web site by Paul Butzi who had a page on calibrating a color head for VC use, including being able to change contrast without changing exposure time. The site no longer exists, as far as I can see. Back then I copied it for my own use, which was to do a similar calibration of an Aristo VCL4500 (2-tube cold light VC head). If anyone is interested I could post it here as a Microsoft Explorer .mht file.

Yes, in 2008 (the first post of this thread) I linked to that site. At least this thread still exists.

john_s · Aug 26, 2023

ic-racer said:
Yes, in 2008 (the first post of this thread) I linked to that site. At least this thread still exists.

oops, sorry I missed that. The link doesn't work any more but might be found on the web archive.

You can download the article as a pdf at

Wayback Machine

ic-racer · Aug 26, 2023

Great find!

john_s · Aug 28, 2023

ic-racer said:
Great find!

It's an earlier version. The one I downloaded as an internet file was revised a few years later. I'll have a look through to see if there's any substantial difference.

Sirius Glass · Aug 28, 2023

I just make exposure strips of Magenta alone and then best of Magenta with exposure strips of Yellow.

ic-racer · Aug 28, 2023

Sirius Glass said:
I just make exposure strips of Magenta alone and then best of Magenta with exposure strips of Yellow.

Are you varying the time or the percentage of filtration? In this tutorial the percentage of color is varied to make a numerical table that prints the same shade of gray at the same printing time.

When varying the printing time (with maximum color), I get a table like this which is something a little different, but works too.

Sirius Glass · Aug 28, 2023

ic-racer said:
Are you varying the time or the percentage of filtration? In this tutorial the percentage of color is varied to make a numerical table that prints the same shade of gray at the same printing time.

When varying the printing time (with maximum color), I get a table like this which is something a little different, but works too.

View attachment 347718

Full Magenta and full yellow ===> split grade.

ic-racer · Aug 28, 2023

Sirius Glass said:
Full Magenta and full yellow ===> split grade.

Split grade, Yes. So indeed one can make a similar table as shown in post #31 with magenta and yellow too. The colored lines (only colored to separate them) represent lines of a constant middle gray value at different contrasts. Similar to the multigrade table. The radial lines are ISO(R) contrast.

Making a multigrade calibration table for color head

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