<p>Thanks everyone. I take Craig's point that contrast is, to some extent, subjective and I guess that's why I was hoping I could adapt (recalibrate?) the Agfa filters to Ilford characteristics. I suppose the difficulty may be an overall loss in range — eg: Agfa grades 0–6 might only equate to Ilford grades 2–4 for example. Robert when you say Agfa filters "loose the right density," do you mean they physically deteriorate through age? The ones I have are certainly old — 20–30 years at a guess — but they're in the original case and sleeves, appear to have been hardly used at all and show no sign of brittleness. Anyway a set of Ilford drawer filters isn't that expensive, I'll probably take your advice, order a set and run some comparisons. Might be interesting. </p>