Originally Posted by leeturner
Yes, the two filters will act as ND. The tables of colour settings that Ilford enclose with the paper come in two sets, one that uses just a single filter (Y or M) and the other that uses a combination of Y and M for each grade. We've found that these dual settings are quite a close match to Ilford's own below-lens filters, so if you want the minimum difference between your two setups I suggest you use these dual-filter settings. The single-filter settings will give you shorter exposures in the middle grades but require a lot more adjustment of exposure when you change the settings. You can (if you use the f-stop printing method) derive a table of exposure adjustments vs filtration which makes life easier.
The business of "consistent exposure" from grade to grade with Ilford filters is a bit of a red herring as it refers only to a specific density (i.e. shade of grey). If you choose the exposure to get the highlights right, you can adjust the shadows using the filters. For example if at grade 2 the shadows aren't dark enough try a harder grade setting, and if they're blocked up try a softer one.
I use a colour head perfectly successfully for VC printing. Some colour heads won't manage a full grade 5, only 4.5, but that's a minor inconvenience compared to the smooth and continuous control of contrast that you can't do with Ilford filters (unless you use the split grade technique).
And don't forget that the correct "grade" is the one that makes the print look right, not a specific number!