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[MarkTonk]

Gregg,

Picoliters is a term used to describe the smallest size an ink droplet is on a inkjet printer and is not used in describing a halftone dot. Measurement of a dot is referred to as dot percentage i.e 49% dot, 2% dot.

You need a densitometer that can be programmed to read "dot percentages" on the press sheet. Typically when finger printing, first make sure the plate has the proper exposure on the CtP. Then output plates with a test chart (if it is a 4 color press, out put the chart on each color, make sure they do not over print each other, you want to be able to read each color on the printed sheet). The test chart will have different steps with dots, for example 2, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, 100. Have the pressman hang the plates and run to his standard densities. Make sure the sheet has also even densities across. Now read each color with the densitometer reading dot percentages and this will tell you you dot gain. The 50% may read 68% (the dot gained from 50 to 68) and this would be very acceptable for sheetfed on a good coated stock. Any way, once you know where you dot gain is, you now have the option of increasing or decreasing it to match your ideal target for gain. This requires knowing what you want the gain to be, it could be based on SWOP or GRACol, or others. If you output dot gain does not match your target, then your rip should have software that allows you to change it so it will. On Heidelberg's MetaDimension, we call this software Process Calibration.

Regards,

Mark