I would probably use delta L* and delta Chroma as a metric for grouping. Since we know when dealing with OBAs, your delta chroma is going to increase from near-neutral to blue in hue (yellow papers would throw a wrench in this).In my experience, you’re going to see increasingly positive a* and increasingly negative b* values as OBAs increase. To keep it manageable, I would say deltas of 3 on L* and chroma for groupings would be reasonable. Terry
On Jun 17, 2015, at 1:06 PM, Mike Stewart <mstewart@embassygraphics.com> wrote:
As I've mentioned before. we are a pre-press provider for publishers and printers worldwide. We use an Indigo Press as a proofer and 95% of the time print/proof is on the actual press stock. This paper is mostly supplied to us by the printer themselves. As I look into our press room I would say that I probably have about 150 different papers; three quarters of which are uncoated stocks heavily laden with OBA's. Using the i1Pro2 in M1 mode I have measured all the papers.
I cannot possibly have 150 different colour managed Hot Folders with individual colour tables based on each stock we proof on. (It would be a nightmare to build and control). I want to group papers into groups based on LAB M1 measurements. Example: 94, 1.0, -9 might be one group. My colour managed Hot Folder would have a colour set up created from 94, 1.0, -9 and I'm wondering if there are any "rule of thumb" tolerances I could use for my groups. Say Group 1 has been set up with 94, 1.0, -9 and my tolerance is L+/- 2, *a +/- 1, *b+/- 2. I could now group all papers that fall within those specs. I realize colour would not be an exact match for each sheet; but should be close enough to allow a printer to "match" the proof.
Has anyone done this and does anyone know if my tolerances are out of whack? My +/- 2 could become quite a large tolerance if ..
94, 1.0, -9 92, -1.0 -7 Is this to large of a gap?
Any help would be appreciated. Mike Stewart