I just bought a used Saunders/LPL 670MXL dichroic enlarger from a portrait studio that sold it because they switched to digital. I performed several tests with several negatives today by setting the yellow and magenta filters variously from 00 to 1 to 2 to 3 and to 4 and making prints at these settings. I then failed to notice a difference in the tonality compared to that I used to get with my insertable Ilford filters in my standard Saunders/LPL enlarger. Is this possibly due to heavy use by the studio and resulting degradation/ wearing out of the internal dichroic filters or is that not possible? I've never seen an illustration in a book or on the Web of how dichroic enlargers are made, so I don't know if their filters can wear out/fade like the insertable ones. Thanks for responding!