QTR 2200 Calibration Help
2004-07-30 by wooismyid
After installing an getting somewhat comfortable with Quadtone RIP, I've started to delve into making some of my own curves. I hit a roadblock right off, and I'm having trouble understanding Roy's documentation for reading the Calibration printout. It reads: ---------- With density, we have 100% cyan = 127 which is between 35% and 40% black => giving 38% black. Its just as easy with Photoshop 100% cyan is 50 RGB info, 35% black is 55 and 40% black is 44 => 37.5%. Either one is close enough. Next, 100% light-cyan is 101, again estimate between 60% and 65% cyan => 63%, with PS 100 light-cyan = 78, 60 cyan = 75, 65 cyan = 83 => giving 63% as well. (Note the math: 83-75 = 8 is 5%, 83-78 = 5 so its 5/8 of the way from 60 to 65 which is about 63% -- remember the values are going down and density goes up). So ltcyan is 63% of cyan which is 38% black. Multiply .63 * .38 giving .24 => meaning ltcyan is 24% of black. ---------- I opened up his sample image in Photoshop and converted to grayscale to follow along as he suggests, but after that I'm lost. I can see that 100% of cyan is eye-dropped in Photoshop to about 93% K, which corresponds to about 38% on the K step wedge. After that, I'm lost. I'm wringing my hair loose-- it's a matter of not getting the math that's laid out in paragraph two, and I'm hoping that someone else can provide some easier to understand set-by-step instructions.