Using spot colours 1

[Trease]

I have a question, when you add a spot colour that is to replace one or more of the process set do you need to delete the empty process channels or just leave them empty?
I spent some time on an image which was a water effect for razors, the black and magenta was replaced with a dark blue 281.
I had both images on screen and mine with the added channel looked spot on against the cymk version.
However if I delete the empty megenta and black the whole colours change and look more yellow!
I do not want to leave the channels in if it is going to look more yellow when printed. (on press not to a inkjet!).
So should I delete the unwanted channels and then make my image look correct?
Hope someone can help!
Trease

 

[zefir]

Trease: really unused channels are simply not sent to the imagesetter.

I hope you can extract some useful information from a previous message:

Here is the fully tested workflow for Duotone applications, including the print of separations, for
PhotoShop and Pagemaker, applied to two different tasks:

Task A: Images are printed with two colorful colors, e.g. blue and green. Text is printed black.
Import image in PhS. Convert Grayscale. Convert Duotone. Assign arbitrary colors and name them
e.g. SpotBlue, SpotGreen. Convert Multichannel. Apply Curves. Save as DCS2 EPS with full
features (but a preview is not required).
Place DCS2 EPS in PM. Write text by (Process) Black. Print separations for Process Black,
SpotBlue, SpotGreen. This delivers 3 plates.

Task B: Images are printed black with an enrichment or tint by a second color. Text is printed black.

Import image in PhS. Convert Grayscale. Convert Duotone. Assign a black 0/0/0/100 and an
arbitrary color and name them e.g. SpotBlack, SpotTint. Convert Multichannel. Apply Curves. Save
as DCS2 EPS with full features (but a preview is not required).
Place DCS2 EPS in PM. Write text now by SpotBlack. Print separations for SpotBlack, SpotTint.
This delivers 2 plates.

The import filter settings in PM: Import EPS colors. 72dpi,TrueColor(Millions..). PM generates a
very reasonable and fast preview by it´s own PostScript interpreter.

The essential problem (which I cannot solve): How can we combine Process Black and SpotBlack,
because it´s essentially the same? My suggested workflow overcomes the problem by writing text
in Spotblack, then Process Black is not necessary. Simply TELL this the Print&Pressman, because
Process Black cannot be deleted, even if it is not used.

Of course all this is valid only in a complete PostScript workflow.

---Gernot