I have recently started using a Durst C35 enlarger for my B & W prints. What I am finding though is when I push up the filter sliders in the block, my exposure time increases (whether 10 x 8 or 7 x 5) and the contrast does not seem to come out. When I do a contract print,the blacks and the whites come out OK. I have filters that seem to fit in the top of the enlarger but to me, this is defeating the object. Can anyone enlighten me if they have experienced the same thing or am I doing something fundamental wrong

I am lower than amateur when it comes to darkroom stuff but any help would be most welcome