I recently purchased a used Omega C760 Super Chromega Dichroic enlarger. Unfortunately, I do not have an owner's manual. Does anybody have the yellow/megenta contrast equivalents for Kodak VC paper? I realize that much of this should be derived experimentally, but I would like to know some good starting points.

-- Michael Riccomini (mriccomini@bak.rr.com), March 15, 2002

Answers

I'll send a printable PDF file to you this weekend. Cheers

-- Scott Walton (walton@ll.mit.edu), March 15, 2002.

In my experience, the published values really aren't worth much of anything -- especially with older units. The darkroom I use has identical enlargers, but the values vary from one unit to the other and then again everytime we change a bulb. Sooo, I highly recommend buying a step tablet and making a series of test prints with it. Try the whole range of filtration on 5x7 paper with 30cc steps in the extremes and 15cc steps closer to the 0 values. Anchell's Variable Contrast Printing gives a good summary of how to do this. Total time about 3 hours which is far less than lost to trial and error.

-- Eric Pederson (epederso@darkwing.uoregon.edu), March 17, 2002.

I agree with Eric's advice to do your own testing. I do things a little differently though. First, I adjust film development so that a photo of a bright-sunny-day scene prints well with no filtration. If I later need less contrast I dial in only yellow or only magenta to increase contrast. I dial in filtration proportionally because the response is not linear. For magenta values might take this sequence: 5, 10, 20, 40, 80, 160. For yellow: 10, 20 etc., since yellow is not as responsive. I don't mix yellow and magenta in an attempt to keep exposure constant because... I don't do test strips, mainly because different densities are at different parts of the print, there's not enough control to suit me. I do test exposures with 1" squares of paper (torn from 1" strips), one exposure per square. I can place them selectively in highlight, shadow, face areas, etc. In a highlight area I'll sometimes place a paper clip on the paper during exposure to get a reference full white. I also use test squares on dodge and burn areas.

-- Tim Brown (brownt@flash.net), March 17, 2002.

Eric, A good possibility why your enlargers are very different is because your filter values are set differently. Dial out all your colors on both and I would venture to say that your values are set differently. If they are, take the front cover off the color head, unscrew the dial and reset the color wheels to zero. Just a thought.

-- Scott Walton (walton@ll.mit.edu), March 18, 2002.