Digital BW, The Print

You're right. Every image is different.

That's why a convert-to-BW program isn't a great idea. 

 Going back to when we had to send three color printers to publications, the
Magenta (Green) was the one used for B&W because it's tone was closest. It
was then put in register with a lighter (very light) black printer.

Blue is still the noisiest and normally can be a minimal value.

Seth

==-----Original Message-----
==From: Walt Farrell [mailto:wftemp1@...] 

==> Thanks.  I guess I get the notion of, say, 50% red, 25% 
==blue, 25% green.
==> The luminance stays the same and we are choosing the 
==weighting of RGB.  
==> But what about a channel value greater than a 100% or 
==negative channel values?
==
==Perhaps I'm still not understanding something, but I'm not 
==convinced that making the numbers add up to 100% will 
==necessarily keep the luminance the same.
==
==Consider an image that was pure red.  Using your numbers 
==above, you keep 50% of the red value and don't add anything 
==else because there is no blue or green.  At that point your 
==image would (I would think) have only half the luminance of 
==the original.
==