condenser & diffusion enlargers--regarding development of negatives

so i know there's a difference in the ideal negative depending on whether you're using a condenser or diffusion enlarger but i'm ashamed to say that i really don't know the basics concerning this rule. and i did a search for this already but the info was vague and scattered so i'm appealing for a basic rundown or if you know a link which would explain it, that's good too.

i have a beseler dichro 67S enlarger but a also have the original condenser head somewhere so i don't know if there's a preference for one over the other (i'm sure that will start a war!)

anyways, any basic or complex info appreciated

The basic difference is that for the same negative under test, a condenser enlarger will produce a more contrasty print (because of the Callier effect) compared to a print made with a diffusion head. To compensate for this difference, the recommendation is to develop film to less contrast if using a condenser head, and to develop film for slightly more contrast when using a diffusion head.

Here we go....

dmax said:

The basic difference is that for the same negative under test, a condenser enlarger will produce a more contrasty print (because of the Callier effect) compared to a print made with a diffusion head. To compensate for this difference, the recommendation is to develop film to less contrast if using a condenser head, and to develop film for slightly more contrast when using a diffusion head.

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ok, makes sense. that's why i tend to like contrasty negs i guess.

does this same info pertain to contact printing also?

and if you have an ideal neg for one head and you print on the other, does that cause a problem or are we talking about slight differences which are easily managed by filters or paper grades? (i'm guessing that it can be managed but that you can never get the same quality print when crossing over?)

People who use both condenser and diffusion enlargers say they have no problem crossing back and forth and getting good results from both. Like most things, experience makes processes easier.

The only discussion based on thorough testing that I've seen on the difference between condenser and diffusion enlargers is in Ctein's Post Exposure, where he spends 13 pages discussing the issues and describing his tests and results. The brief summary of his results takes half a long page. He says that Callier's discoveries aren't on the scale of photographic emulsions, but on structures that are smaller than a wavelength of light, so don't apply to photographic printing.

His tests across several films and papers shows that when matching overall contrast, a condenser tends to print highlights with greater contrast and shadows with less contrast. So the diffusion head has less tonal separation in extreme highlights, but more open shadows. The degree to which this is true varies with changes in film and development.

The whole book is well worth a read, and the issues discussed in the section on condenser/diffusion enlargers are more complex than any brief summary such as this post.

Lee

What Lee said: Ctein is the only person who made a test that really matters about diffusion/condensers.

Ctein is the only person who made a test that really matters about diffusion/condensers.

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Here, here. 'Post exposure' is a great read. Ctein and Mr. R. Hicks are my two favourite writers on photographic matters.

To muddy the waters, most condenser enlargers use frosted bulbs, so are really semi diffusion. A true point source, small clear bulb with condenser will show more contrast and grain. I converted an old Russian point source to 110, and the results are dramatic. Not having read any data based on test results was the testing based on a point source or semi diffusion?

I no longer use the diffusion head. Condenser only - sharper contrastier prints. - Negs can be slightly flatter. It is the way to go.

they used to say on the film box
to process film about 30% more if using
a cold light head ... YMMV