Quote Originally Posted by Molli View Post
Matt, regarding the size and shape of the bulb, I've just switched out the 75W bulb from an old Durst 606 enlarger into my Durst M600, replacing the 150W globe which was giving me ridiculously short exposure times, even stopped right down. I intended to run some tests anyway, but you've just given me something else to look out for. The 75W bulb is slightly smaller and narrower than the 150W. Do you think this might be much of an issue?

I have a Kodak Wratten ND .20 filter which I was intending to use but my concern with it is how stupidly hot the enlarger gets so I thought I'd try the other bulb out first.

(Apologies to the OP if I seem to be hijacking the thread but I hope any answers elicited to my question might help others also with regard to replacing bulbs... that's my excuse anyway )
It's the same concern.

Is the bright part of the bulb where the rest of the optics of the enlarger expect it to be?

There are tests you can do that check how even the light is, and whether all the corners of your negatives are properly illuminated. Printing a slightly fogged piece of film is one of them.

Some times you can add extra diffusion to even things out, but that changes the character of the illumination, which is one of the strengths of Durst enlargers.