Replacement lamp for Durst 138S?

[Michael Mutmansky]

Greetings folks,

I am looking to convert my Durst 138 back from an 8x10 enlarger to a 4x5 enlarger, but before I remove the 8x10 head, I want to figure out exactly what this is going to cost me...

I know about the Jensen $800 lamp conversion, but that seems ridiculous for an enlarger that cost less than half that in the first place, and I don't particularly want a point source.

Can anyone point me toward a large globe lamp substitute for the discontinued Opal lamp? Are there any other options out there for the 138 condensor head?

---Michael

[wfwhitaker]

I'll be interested to see what responses you get. I've been under the impression that you could simply use a PH213 bulb.

[Michael Mutmansky]

Will,

That may be true, but I doubt it for larger formats. The PH213 is 66mm in diameter, and Durst recommends that for 4x5 and larger formats a 110mm lamp be used. Unless they are being extremely conservative, I suspect there will be problems with uniformity with that lamp.

I thought I had seen reference to another lamp retrofit option out there, but I don't ssee it now, and I'm curious whether the Jensen option it the only viable one.

---Michael

[Richard Wasserman]

Michael,
I had the same problem and convinced myself that the Jensen conversion kit was my best option. After a number of delays it should arrive early this week. The new light source will be adjustable from a point source to full diffusion and is bright (although it can be dimmed) which will help with some of my fairly dense negatives and bigger enlargments. Whether it's worth $800 remains to be seen...

Richard

[wfwhitaker]

"The PH213 is 66mm in diameter, and Durst recommends that for 4x5 and larger formats a 110mm lamp be used."



That's interesting since the Pulam, the lamp used for the point source configuration, is much, much smaller than even the PH213. And it's used for at least up to 4x5.



It would seem that if the bulb is placed at the correct point optically in the condenser system (the conjugate or whatever it's called) and the correct condensers used, that its physical size shouldn't really matter as far as evenness of illumination is concerned. And the Durst has such a nice XYZ positioning device for the bulb. Just curious....

[Michael S. Briggs]

Unform illumination can be obtained with a small bulb that approximates a point source. One effect of the bulb size is the degree of collimation obtained from the illumation system.

One extreme is the condenser head with a point light source. Even illumation is obtained by positioning the lamp and condensers so as to focus the lamp on the enterence pupil of the enlarging lenses. The light passing through the film will be highly collimated --- each spot on the film is illuminated by light rays arriving with a narrow range of angles.

On the other extreme are diffusion heads, such as "cold lights" and color heads that cause a sheet of diffusing material to glow just above the negative. These diffused light sources produce light rays that reach the film from a wide range of angles.

In practice, condenser enlargers for pictorial use (vs electron microscopy, etc.) typically have fairly large light bulbs. This causes the condenser to image many points of light and produce illumination that reachs each spot on the film with a range of angles -- midway between a point source and a diffusion source. This illumination is normally termed collimated even though it isn't perfectly collimated. These enlargers are more practical to use because the point source enlarger emphasizes dust and scratches and requires precise positioning of the point source to obtain even illumination -- even to the extent that the bulb might have to be repositioned for different print sizes. With a larger bulb, a small error in the position of the bulb will still produce acceptably even illumination.

So the bulb size will change where your enlarger falls on the range from highly collimated light to highly diffuse. A smaller bulb will increase print contrast, emphasize dust and scratches and require careful positioning.

I can't say exactly how your enlarger will peform with the various bulbs, but the theory tells you the possible problems from using a smaller lamp than recommended by the manufacturer.

[lee\c]

I am currently using a PH301 bulb that I found in a used photo equipement store in Dallas. Before that I was using a PH213 and it seemed to do the job. The PH301 looks like a regular lightbulb on steriods and it barely fits in the head of the 138s. I think that this bulb is a 300 watt bulb, however, unless I can find more bulbs like this one, I intend to use the PH213 again.

leec

[Nick_3536]

My Beseler CB-7 uses a Ph212 for 4x5. The bulb is just fine with the big 7" condensors. Is the PH301 a medium base bulb?

[wfwhitaker]

"One effect of the bulb size is the degree of collimation obtained from the illumation system."



This is essentially what I was alluding to. Michael, why don't you try a PH213 and see how it works for you. It costs a lot less than the Jensen conversion. I've got both the Opal bulb and a PH213 on hand. When I have a chance I'll make comparison prints to satisfy my own curiosity.

[Michael Mutmansky]

Thanks folks.

It sounds like the size of the lamp is important if you don't want to be too careful with the magnification ratio, but if you pay attention, a smaller size will work suitably well. Is that a fair characterization?

I'll be looking into the PH213 lamp, as it seems to be readily available.

My head has a Lacalo 2 insert, which is a piece of heat rejecting glass in a metal frame. I believe that Durst recommends using the Lacalo 2 if the lamp wattage is over 200w. The coating on the glass is ruined, so I need to determine what may be a good replacement or whether there are any Lacalo 2 parts out there that I can get my hands on.

Also, I'd like to get a hold of a suitable set of multigrade filters for the filter frame. The frame doesn't appear to accommodate a flexible filter, but it may be possible to make a sandwich frame to hold a flexible filter. Are there other options? I could put the filter under the lens, but would prefer to not do that if I can help it.

What else? ... I would like to find a good glassless 4x5 negative carrier. Any recommendations? Something that will give me as close to full frame as possible. I've been having problems with newton rings with my preferred film (Fuji Acros 100). It seems that the emulsion side is smooth enough to cause some difficulty. I understand this is also a prolem with TMY.



Many thanks for the great advise so far,

---Michael