Gray Scales

These 3 frames provide a reference in scanning pictures with gray scales on Kodachrome and Ektachrome.   When scanning color pictures which incorporate gray scales, allowance should be made for reciprocity differences among the dye layers.  This results in slight color casts in gray areas with differing tones.  Assuming all steps are reproduced on film as gray could result in distortions of other colors when corrections are applied. The gray scales were measured on 3 types of film: Plus-X, Kodachrome 64, and Ektachrome.  The Q-14 black and white scale was shot on Plus-X and Kodachrome 64. The Q-60 calibration slide was used as an Ektachrome test.

Q-14 Gray Scale

After a step was arbitrarily chosen as a reference gray, the steps below and above were measured with a color analyzer.  The measurements showed the corrections in CC required to maintain the chosen reference color.

Plus-X, a black and white film, was chosen to provide a manifestly gray scale for scanning.  Since it is a negative film, step 0.0 is black.

As expected, the color analyzer indicated that there was no trend in color cast going from step to step.

Kodak Q-14 Shot On Kodak Kodachrome 64

The gray scale shot on Kodachrome starts at the 1.9 step (black) with a blue-cyan cast (relative to the reference step) and follows a yellow-red trend to the 0.0 step (white).

Kodak Q60-E3 Calibration Slide (Ektachrome)

Above the reference step, there is a slight trend to a green cast up until step 0 (white).  Below the reference step, there is a pronounced red-magenta trend to the darkest step.

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