Re: Tints of L*a*b* colours
> If one is dealing with a LAB colour (or, you've measured a Pantone colour), how could one determine what a tint of that colour would measure in LAB, without having to actually print it out.
For solids, you could use a round trip (Lab->CMYK->Lab) through an ICC profile using absolute rendering. but for tints, well, there's a problem there. Pantone does publish tint books, but I don't trust them as they're all over the place for gains. , though you could expect similar Lab values for simlar tints using simlar substrates.
Other than that, this is kind of a black art. We've run into this problem from a proofing perspective and the best results, short of a press test of the spot color with tone scales, came from dialing in the solid to the closest delta E and then ensuring a dot gain curve representative of the printing is applied...assuming 20% gain for example. We're using GMG for proofing and spot color accuracy, including tints, come out fantastic with this method. A few curve balls though...gamut limitation of the proofer of course, and when tints mix with process colors, things get tricky, but this is still the best approach we've used, short of multicolor profiling.