Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, 
"sjhenry" <sjhenry@y...> wrote:
> <E.Dinkla@c...> wrote:
> > I will ask a befriended programmer to take a look at the ACV 
file
> > and how a Spectrocam reading can be used to make one.
> > Might even be easier to go to a grey profile directly if any
> > curve to profile conversion is creating RGB flaws in the 
process.
> > Ernst
> 
> ACV file format for gray scale curve is as follows
> 
> Bytes    Description
> 0-1      Magic Number??? always 1
> 2-3      # of curves (for gray it is alwasy 1) 1
> 4-5      # of points in the curve
> 
> 6-7      Old value for first point on the curve
> 8-9      New value for first point on the curve
> 
> 10-11    Old value for second point on the curve
> 12-13    New value for second point on the curve
> 
> and so on for each point on the curve.
> 
> "Old Value" means the original RGB value for that gray ranging 
from 0 
> to 255. "New Value" means the RGB value obtained after 
printing the 
> target ranging from 0 to 255. Also I assume in gray scale r = g 
= b.
> 
> RGB curve essentially the same but with 3 individual curve for 
r,g 
> and b. These are from my observation. So verify it in a hex 
editor 
> what I told is correct or not.
> 
> Jones.

I think the old and new values are reversed.  In Photoshop 
lingo it looks to me to be Output then Input. 

Also with RGB and CMYK I see 5 curves and 6 curves
respectively.  The first one is the composite RGB or CMYK,
followed by the individual RGB or CMYK, and then at the
end there always seems to be an extra curve that is just
(0,0) to (255,255).  I have no idea what this last thing is but
all the acv's I've seen have it.  Maybe there's some hidden
feature to PS.

Roy