Digital BW, The Print

Bob Frost wrote:

>Results
>
>Only Photoblack was used at 0/0/0 and 5/5/5, but at 15/15/15 magenta, blue, 
>cyan, and yellow were used as well.
>
>The amount of photoblack decreased steadily up to 105/105/105, and was 
>absent from 115/115/115 upwards, while the amounts of magenta, blue, cyan 
>and yellow increased steadily from 15/15/15 to 105/105/105. Red was not used 
>anywhere.
>
>Glop was not used until 105/105/105, where it's use overlapped with the 
>disappearance of photoblack, and its use increased from then on to 
>255/255/255, while the amounts of magenta, blue, cyan, and yellow decreased 
>steadily.
>
>At 255/255/255 only GLOP was used.
>  
>
Interesting and nice work Bob.  I'm surprised that the Photo Black 
Generation starts at 105-115 so approx at 59-55% CMY, even on the old 
wide formats (9000) with fixed bigger droplets it was at 50%, one would 
expect the black generation to start earlier with a 1.5 picoliter 
droplet size. The 15/15/15 point  for having all inks working isn't 
unusual..
The continuous use of Blue throughout in the grey patches is a surprise 
too. It would have been understandable in compensation for the warmer 
black till say 115 but not in the lighter areas. There are several 
methods to use Red and Blue instead of MY and CM mixes in N-color 
inksets but the more neutral the image is the less the extra hues 
normally appear. Usually they are used where the normal color mixes 
deliver less gamut. Maybe Epson profiled the normal CMYK ink set to the 
warm side over the full range and neutralised the total with Blue ink 
added. N-color profiling isn't easy and asks for dedicated profilers if 
the printer profile isn't an RGB one. If it is an RGB printer profile 
like in this case then the distribution of the inks has to be done 
somewhere else = the paper setting.

Ernst