I have an Omega D-3 VC Autofocus enlarger which uses a caming system of focusing tracks to position the lens stage and the film stage in a correct distance for projecting an in-focus image on the baseboard. The focusing tracks are calibrated to a specific enlarging lens. Since I do not have the original lens that I have tracks for, I would like to fabricate new tracks that would at least get me into the "Ballpark" so I could manually fine focus at a variety of enlargement lens to baseboard distances. Does any one know how the varying widths of the tracks are computed so that the track will cam the stages into alignment? I have made tapered simulated tracks but can use only for a single focusing position. I have the Simmon Omega instuction booklet but no information on design of the auto focus track. I would like to use an 135 mm enlarging lens as a start point. Thanks ...

-- Russell E Brubaker (brbkr@macs.net), August 28, 1999

Answers

Hi Russ,

Been there, done that! Remember that these enlargers were around way before computers. I believe that Omega had some sort of mechanical system that allowed them to create the tracks for a given lens. I'm guessing here, but I suspect the curve remained about the same for a given focal length, and only its location on the track changed. I haven't found a big difference between tracks for the same lens focal length, but I'm sure there is some. You can cut tracks out of thin aluminum, quite a bit thinner than they used, in fact. You have to use a 1" thick easel. Cut a "blank" and install it. Set the focus knob at a mid position, then hold the whole focusing assembly at the correct spot and mark the blank where the big wheel would have to hit it. Do this for as many spots as possible, then cut the blank. It will be surprisingly close over short distances. It won't be perfect. With some careful measurements, and the use of a cad system, you could probably derive the math to plot it exactly, but the geometry is fairly difficult. If you can get a track for the same focal length, you can easily trace and copy it. Unfortunately, my tracks are all labeled by serial number, not focal length, and I don't have any original lenses that went with them either. Email me if you want to have a more extensive gab session about this project.

-- Conrad Hoffman (choffman@rpa.net), August 28, 1999.

I used to own a Berkey Omega "Universal ProLab 4 X 5", an "autofocus" variable condensor enlarger. I bought it as state govt. surplus and it came without a lens. On the cams it specified not only the lens manufacturer, focal length and model, but a number which seems to have been applied by the agency using it, that refered to the lens' serial number.

I didn't know any better and used the 50mm Schneider I had as well as the 150mm Rodenstock I purchased subsequently. I never enlarged above 16 X 20 but had no perceptible quality problems which I could link to the enlarger/cams/lens combo - they were usually all "pilot error". It seemed to work quite well when I changed enlargements from 8 X 10 to 11 X 14 but I always checked anyway before stopping down.

Your Quality Threshold may well be much higher than mine, and if you have the know-how and experience to carry out this project that may well be, but I wouldn't sweat it. Make some prints with your set-up as is and see if you like 'em. Show 'em to experienced photogs and see if they say, "Oh, I can see here where your enlarger focus cams don't match your lens".

-- Sean yates (yatescats@yahoo.com), August 29, 1999.

My D3 came with one cam and it didn't match the lens. I used it as a template to make the others. I sized the cam blank so it was a bit bigger and I could cut away the extra material. To work up the curve I started with the focus knob in the middle of it's range and the head at the top. In low light and with a test negative in the carrier I fiddled the cam wheel back and forth beside the cam and when it was in focus made a mark beside the wheel on the cam. I made these marks every 1/2" or so as I moved the head down to the bottom. I then cut the cam along side the marks I made and then smoothed it with emery cloth. I then tested out the cam and if there were high spots I took them down a bit.

This all sounds hard but it took me about 1/2 hour to make a track and maybe another 1/2 hour to tune it up. Contrast this with at least a day to develop the form mathematically based on not so accurate assumptions.

If you wish, I could make a paper template of the original 135 mm track I have.

Cheers,

-- Duane Kucheran (dkucheran@creo.com), August 30, 1999.

Too All.. Thanks for the interesting responses. I use the 4X5 so infrequently that I haven't taken the time to cut out a new track . I found out that poster board is the right thickness and I've even bought an alumium yard stick that could be used for the full run of the track. This site has given me new insight for help on the whole spectrum of dark room inovation . Still like to see the diagraming used to design those calibrated focus tracks !! Russ...

-- Russell Brubaker (brbkr@macs.net), August 30, 1999.

I worked in a pro-lab once that had one of these for it's B&W custom work but I don't ever remember the auto-focus being accurate enough to trust or that much faster than a rough-focus then fine focus on a manual focus enlarger( it's really more a gimmick than useful)...so if it's just to restore the enlarger I suppose I understand but don't be surprised if you end up focussing as much as will on one without autofocus. Terry Seaman at photomall has a bunch of parts for d-series enlargers try www.photomall.com

-- trib (linhof6@hotmail.com), August 31, 1999.