Digital BW, The Print

Hi Roy

You know this stuff much better than I do but as I understand it there are 4
parts to any A2B0 (or other like tag):

1. The identity matrix - a given for Lab PCS
2. The 1D input table (curve)
3. The multidimensional CLUT
4. The 1D output table (curve)

You've used 4. to generate the transform rather than 3. If PS normally goes
looking into the CLUT for bpc generation etc then what will it find?
Colorsync portrays the CLUT contents as perfect lab.

Thinking about it a little more, I guess PS would most likely pass data
through the entire transform 1-4 but I am just speculating.  If that's the
case, for a single channel situation it doesn't matter where in 2-4 the info
is kept.  But I am puzzled though by a comment you made some time ago
(probably offline) that PS bpc did not work with the new profiles and so you
had to build it in.  It suggests PS is not finding the data it needs.  (Of
course it all works in the end because you have done the bpc for PS.)


> From: Roy Harrington <roy@...>

> 
> 
> Only the OutCurve is used since both directions only have one input channel.
> You can have 3 sets of curves for the different intents but the "0" curve will
> be used for all if the others don't exist.

Yes. My question is whether you use the output table or the CLUT.

>The softproof is based on the
> A2B0 curve and although potentially
>there could be 3 different soft-proof curves
> there's no way to select which one is used for the reverse direction, nor can
> you select BPC on/off for the reverse.  So you must decide where the black is
> mapped before making the profile.


I'm not sure I follow you here.  Presumably PS would normally look to the
correct intent tag as per Bob Frost's earlier post.  That is there wouldn't
be "3 different soft proof curves", per se, but rather PS would look to the
relevant intent depending on the settings checked in the soft proof.  (I
don't see any other profiles using 2 or 4 above.)  We just have one intent
so each time it looks it comes to the same place.  I guess I need to think
this through a bit more. Hmmm.

Steve