The settings on my condenser are marked for negative sizes (35 mm, 110, 2 1/4x2 1/4, ...). I just happened to read a note in the archives which said that you should be setting it for the lens size, not the negative size. I assume that 35mm corresponds to a 50mm lens and 2 1/4 corresponds to a 75mm. What setting should I use for an 80mm?

-- Peter Schauss (schauss@worldnet.att.net), April 05, 2002

Answers

2 1/4. Interesting note, which archive? I have never heard or read that before and have always change per negative size.

-- Ann Clancy (clancya@attbi.com), April 05, 2002.

Depends on which 80mm lens you are referring to. The Schneider Componon-S 80mm claims to only cover up to 2 1/4 square, but both the 80mm El-Nikkor and 80mm Rodenstock Rodagon claim to cover 2 1/4 x 2 3/4 (6x7). I have found the manufacturer claims to be accurate. Focal length is not the sole determination of negative coverage. (Interestingly, both El Nikkor and Rodenstock use 105mm lenses to cover 6x9, but Schneider claims that their 100mm Componon-S covers 6x9.)

I do not know whether the advise about setting the condensers is correct. I would think that the only considerations are the evenness of the illumination vs. the intensity of light source, which may vary depending on the enlarger head. As a general rule, the wider the illumination, the more even (but the less intense) the light, but there may be exceptions. The only way to know for sure which setting is the best compromise of evenness and light intensity for your enlarger/head combination is to conduct a test.

-- Michael Feldman (mfeldman@qwest.net), April 05, 2002.

You're trying to optimize the light path so that most of the light passes through the enlarging lens. That's determined by the focal length, not the negative size. Since most people use a lens about equal to the neg diagonal, the chart is usually fine. Enlargers are a pretty sloppy optical device- broad source, simple condensers, so the setting isn't terribly critical. I'd be most worried about evenness of illumination, so if running the condensers a bit higher or lower works better, do it.

-- Conrad Hoffman (choffman@rpa.net), April 05, 2002.

The typical condenser 23C apparently won't produce uniform illumination at any setting; so just find the condenser position that gives the least variation across the image. My 23C puts about a half stop less light at the bottom of the image than the top, with corners being dimmer than the center.

-- Keith Nichols (knichols1@mindspring.com), April 06, 2002.

A couple 23C tricks. First, find out how bad it is. Put a piece of evenly fogged film in the carrier and print it to a medium gray on #3 or #4 paper. You must have film in the carrier to see some of the problems. Falloff? Donuts? IMHO the bulb is too small for the condenser design. If it has darkening the illumination will suffer, so treat yourself to a new bulb. Related to the size problem, the area above and around the bulb tends to get imaged onto the film plane. This creates donuts in even sky areas. Paint the area above the bulb pure white, but not the light trap. The 23C condensers are *not* identical. One has a flat surface, the other is convex on both surfaces. The mild convex surface goes next to the negative. The flat surface faces the bulb. If the side-to-side slop of the condensers tends to cut off corners, glue a toothpick in the channel to hold the condenser pack in whatever direction fixes the problem. Always install the pack the same way. Buy the heat absorbing glass and pretend your negative carriers don't have a rolled edge near the cutout that lets the flim wander as it heats up. (if you have a 23CIII with the larger bulb, ignore all this- they fixed it) Hopefully something here was useful...

-- Conrad Hoffman (choffman@rpa.net), April 08, 2002.