Got a real world example and questions about it.
I created a basic ink limit checker based on K=100%; 60 patches at 5% intervals, from 100% to 395%. Printed this and measure the patches via Eye-One Share, open this file via Measure Tool and export Lab values. Plotted the resulting Lab values along side calculated Chroma and Hue values.
The Lab_a and Chroma curves mirror each other for a while and then diverge with Chroma rising and Lab_a declining. The Lab_b and Hue curves mirror each other as well for a while and then diverge with both Lab_b and Hue decreasing but Hue decreasing at a more rapid rate than Lab_b. The point at which divergence occurs in the above examples is only one click, 5%, off from each other and the point at which Lab_L bottoms out is 3 clicks or 15% off from the afore mentioned point of divergence.
When considering Total Ink Limit; 1. Is the point of divergence I'm observing an indicator in determining total ink limit? Of not is any of this information usable in helping to determine TIL? 2. How much weight should the bottom-out point of the Lab_L curve be given when determining TIL.
Can this same procedure be used for testing linearity and determining channel limiting? Would Chroma and Hue be good guides? If so, how do you use Chroma and Hue curves/values to aid in linearization and channel limiting?
Douglas Rhiner Technical Director / Owner High Mountain Imagery O. 530-546-0413 C. 530-362-0047 www.hmitahoe.com
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