Dear forum members
I have read the posts on this topic with much interest. The next forum topic, split filter printing appears to be dealing with the same issue.
It is my experience that:
If we are making a straight print, ie. where the whole print gets the same total exposure, then
1. If a print with a particular appearance can be achieved with the split grade ( aka split filter ) technique, then exactly the same print can be achieved with one exposure. It may be necessary to use an intermediate grade ( such as G2.75 ) however this is easily achieved with a dichro colour head. In fact in practice, intermediate grades are not often required.
2. The one exposure method is much quicker and easier,especially if we use an RH Designs Analyser Pro as I do. This equipment if properly calibrated gives very reliable, accurate exposure times and contrast grades.( I have no commercial relationship with the manufacturer or any distributor or retailer of this, or any other product. )
3. The reason for this is easier to understand if we consider the enlarger light source being directed through a dichro colour head. This filtering method exposes every print ( except those made on 0Y+ MaxM or 0M+ MaxY) through part of a blue filter and part of a green filter. Actually the filters are yellow=(green+red) and magenta= (blue+red) but the printing paper is insensitive to the red component.
It matters not at all to the printing paper ( apart from lamp ramp up effects and paper reciprocity characteristics) whether the proportion of blue and green is achieved by differential time exposure ( as in split filter printing) or differential movement of the filters across the light source ( as in a colour head).