Santa is bringing me a new (to me) toy... a X-Rite Reflective Densitometer... (Model 418 with a 3.4mm aperture if it matters).
anyways... I assume the correct usage is to make a screen, then throw some ink in, print and then take readings of the 10-90% half tones and use those numbers to calibrate the rip (I-Block in my case on the I-Image).
do I subtract what's already there (looks like a 45 degree line from 0 to 100), so for example if the 50% halftone block is coming up at let's say 70% due to dot gain, do I enter 30% to bring it down 20%??
The next question is, I assume that I'll end up with different dot-gain curves for let's say 45lpi on a 225S mesh vs 55lpi on a 305 mesh...
do I do a different calibration curve for each?
is this an iterative process, where you have to dial it in slowly (ie do the first one, set new settings, burn new screen with new settings, check again, etc?)
On calibration of the densitometer itself, I'm assuming that calibrating to the manufacturer 'standard' isn't what I want to do, and that I should calibrate to the white of the shirt itself?
Anything else I should be aware of/watch out for?
If you haven't already,you can download this file.
http://www.theshirtboard.com/index.php/topic,13579.msg131989.html#msg131989and use that for your test. It should be similar to something that your Tech may have printed out during his install but this will be a little more specific.
When printing, use black ink at 55lpi on whatever mesh with semi thin ink, allow the inks and pallets to warm up. For example, warm the pallets up and then print about 5 or so test prints and then print. Cure, then use the new toy.
Initially don't make any adjustments to what your I-Block is outputting at.
Print your test, and in the 50% area, you read your printed result. Then you subtract the % of dot gain from the 50% (input) section. Your output should be less. No two shops will have an exact dot gain curve.
Typically, you would not have that big of a difference just by switching from 45 to a 55lpi, but yes, in that case. from a 225 mesh putting down more ink I'd say yes, you may want to look at using two different curves. The results will be slightly different, most notably in the shadow tones from the 65% range and up to 99%. Still tho, the curve may only change slightly.
You will have to dial it in slowly. Maybe making as many as 3-4 adjustments.
Yes, you will need to zero out the device, both on the white of the shirt and the black (solid) of the print.
