Quote Originally Posted by Oren Grad View Post
You can run your own tests to establish exposure compensation factors to match any particular tone - say, middle gray. Also, some paper manufacturers provide tables of magenta/yellow combinations that maintain consistent exposure for different effective grades.

Either way, though, that only gets you into the ballpark. The best exposure for a different contrast grade isn't necessarily going to be the one that matches any particular tone with its rendering in a different grade. You can expect to still have to do some trial-and-error tweaking.
This is very good advice.

I've calibrated my Aristo VCL variable contrast head using a step wedge. I chose the highlights (threshold) to standardize against. I found that for this head there is almost exactly a 10x exposure difference between the softest (all green light) and the hardest (all blue light) grades of Ilford MGIV FB/RC. By creating a table of exposure compensation factors for each quarter-grade in between, I can pretty much make any grade change in one-quarter increments and come very close to matching the correct exposure change on the first try. Usually a single test strip confirms the new exposure, if there is any doubt.

This is a great time saver to put me in the initial ballpark with a minimum of fuss. Fine adjustments at the new base contrast can then begin immediately. Saves time, saves paper, saves frustration.

I don't see why you couldn't do the same with a color head.

Ken