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ABW - Fine Tuning Your Monochrome Output - part 4 of 1 2 3 4 5 6 7

by Mike McNamee Published 01/08/2012

The first question we had to answer was how big is the size of the shift in a print for a point shift in the ABW colour wheel.

Mathematically this is quite tricky to compute because of the negative numbers that are kicking around in both the Lab plot and the ABW Color Wheel. A bit more squaring, square rooting and Pythagoras sorted that out and eventually we arrived at a value of 10 as the multiplier - that is 10 units on the ABW scale produces a 1 Lab unit change in the tone values of the print. The reality is more complex because of the offset produced by the paper white (even the Canson was a little off white) and statistical noise within measurements.

We noted that points on the green and yellow scales in ABW seemed to reproduce a larger effect than anticipated, those in blue and orange lesser than anticipated (by this time we had run out of paper!). However, as a first cut the concept works moderately well and so we progressed towards solving the soft-proofing issue.

Soft proofing

To bias a monochrome view in Photoshop by a specific amount we used the following method:

1. Open the target monochrome image in Photoshop, which should be flat for simplicity.
2. Make a new Color Adjustment layer and choose a 50% grey.
3. Set the adjustment layer mode to 'colour' which should recover the image view to the original, neutral monochrome.
4. Double click the adjustment layer to reveal the 'Pick a Solid Color' panel.
5. Change the Lab values to 50% L and then an a or b setting to match one tenth of the proposed ABW settings. In this case the a value (plus or minus) is equivalent to the horizontal value in ABW, the b value is the equivalent 1/10 of the vertical value in ABW. Thus if you wish to soft proof ABW values of 50v: -30h you would set a to -3 and b to +5.

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1st Published 01/08/2012
last update 21/07/2022 08:46:22

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