ArgyllCMS B&W targen

[Graeme Gill]

I tried to read the black, white and grey patch chart with the ColorMunki Photo as usual. But it produced "too many patches" error almost every time and could only be coaxed into the occasional successful column read.

According to the targen verbose output, there should be heaps of contrast between the patches and colored spacers (nearly 60 Delta E), so it's strange that you had problems. You could try increasing the space width slightly, using the printtarg -A option, i.e. "-A 1.5".
Another thing to try is to use just grey spacers (printtarg -b), although in theory they will have a worse contrast for the patch recognition.

Looking at the typical A4 colour patch chart it became immediately clear that ArgyllCMS never places light colour patches in the top and bottom rows (i.e. the start and stop points) on the A4 sheet.

By default the patch order is optimized to maximize the worst case contrast between patch and spacer color, to maximize reading reliability. Since at the end the paper is white, this will influence what patches are at the ends. The patch/spacer contrast should be fine though.

 

[Emulator]

@Graeme Gill

Many thanks for the explanations.

I clearly haven't understood the targen options.

targen -v -d2 -G -e4 -B4 -g949 -f957 %pcn1%

g = Grey axis RGB or CMY steps, so in this case do I leave f blank and make g=957?

On reading the grey patches the ColorMunki failed to produce a response on all but a few rows, the few that did respond had the darker end patches.

 

[Graeme Gill]

@Graeme Gill
g = Grey axis RGB or CMY steps, so in this case do I leave f blank and make g=957?

If you don't want any full spread patches, use -f0 to override the default of 836.

 

[Smile]

@Graeme Gill

Is there a way or tool to chaotify target patches by specifying target reading direction? The colorlab v2.8.13 does this only for i1 type spectrophotometers (long page size), for isis ot others there is need to specify the chaotify patters in other direction (short page side).

 

[Graeme Gill]

@Graeme Gill

Is there a way or tool to chaotify target patches by specifying target reading direction?

Sorry, I don't really understand what you mean. By default i1 and Munki strips are optimized so that ArgyllCMS can automatically recognise the direction the strip is read in. ArgyllCMS doesn't currently support the iSis.

 

[user5800]

For @Emulator and @Graeme Gill

A simple question regarding Argyll and B&W profiles.

Putting aside the 16 bit, if a targen is cast with 256, sorry 254 greys (+ white and black) interpolation is still used? I mean with all 256 greys all 8 bit variations from 0,0,0 to 255,255,255 should be matched leading to an almost perfect neutral grey profile.

What's the need of going up to 957 patches?