Normally each paper maker gives instructions with the paper for both single and dual filtration and for sets of enlarger groups which gets you close but bear in mind that dual filtration will not give exactly equal exposure times for each grade. You can calibrate for each grade using single filtration but this requires a bit of time.

You can also check Ralph's Lambrecht's site "Darkroom Magic" where he gives compensating exposures in fractions of a stop for Ilford and Agfa paper to retain the highlight zones of either VII or VIII8.

Using Ilford filters will give you the same exposure time for grades up to 3.5 and then for grades 4 &5 you need twice the exposure. This makes things simpler as it removes the complication of allowing for different groups of enlargers.

Do the Ilford filters ensure that the key highlight zone of ZVII or ZVIII remain the same? I don't know but don't worry as my post will only be the first of many on the subject so much more info will emerge


pentaxuser