I believe that diffuser enlargers naturally tend to produce slightly less contrast than condensors (all other things being equal).

ON THE ASSUMPTION THAT I AM TRYING TO PRODUCE HIGH CONTRAST:

Compared to use a condensor enlarger, if I were to use a diffuser enlarger, and increase contrast using high graded paper (or equivalent filtration on VC paper), will the result be the same? Or will this in effect be trying to "force" it, leading to slightly lower quality results?

All advice and views much appreciated!

-- Ed Hurst (BullMoo@hotmail.com), April 06, 2001

Answers

You could try to increase contrast by developing your negatives a bit longer, but your other option would be to use a higher contrast grade of paper or a high-contrast paper developer. The old Brovira grade 5 was incredibly contrasty, but Ansel claimed that Oriental grade 4 was even more so.

-- Ed Buffaloe (edb@unblinkingeye.com), April 06, 2001.

Ed, Changing any of the myriad of variables within the photographic chain, you'll never have any result equal to each other. Curves always bends this or that way, and it can be quite confusing to stablish a clear cause/consequence relantionship. But some facts can be remembered: when you achive more contrast by film development, you're also changing some of it's structural characteristics, such as grain, resolution, local contrast, etc. And you can't change your mind! On the other side, it can be so easy to test the perfect amount of contrast just changing filters on printing stage. You can't make unforgivable mistakes on the lab. But sometimes it can be quite unconfortable to work with heavy filtration, grades 4 to 5, for the small exposure latitude they offer. Differences on enlargers heads can be too small, if you really mean HIGH CONTRAST. In conclusion, it may sound reasonable to achieve contrast increase by steps, through filtering on camera, film development, clear opticals, paper grade, etc. This way you can fly high on contrast without much confidence on a single step, wich can or can not work as planned. Good luck.

Cesar B.

-- Cesar Barreto (cesarb@infolink.com.br), April 06, 2001.

Results won't be exactly the same, no. The diffuser enlarger gives a true and linear translation of film density to the paper. A point source condenser enlarger shows a phenomenon commonly called the 'Callier effect'.
More precisely, it reveals the differing Callier coefficient of the negative, where the higher densities diffuse light more than the lower ones. This has the effect of increasing contrast, in a non-linear way, where the shadow detail of the print has greater separation than the highlights. This is almost impossible to emulate any other way.
Most so-called condenser enlargers use a diffuse bulb as a light source, and the light produced is really semi-diffuse.

-- Pete Andrews (p.l.andrews@bham.ac.uk), April 09, 2001.