Printing results from Durst 138S lamp retrofit
I have printed several images recently with the lamp retrofit that I designed for the Durst 138S that I have.
Until about three years ago, I printed exclusively with a cold light head and later with the diffusion Saunders 4550 VCCE. (An enlarger that I still own by the way).
Personally, speaking for myself, I thought that I got results more to my tastes when I switched to the Durst enlarger. The problem that arose is that the Thorn lamp for that enlarger is no longer available.
To deal with that problem I located, procured and designed a retrofit using a 1000 watt halogen lamp rather then the 250 watt Thorn lamp. In the design of this I arranged for the enlarger to be used as everything from a point light source to the diffusion of a cold light head. The design process was quite extensive and creating a reflector design was a major problem to overcome.
I have never seen grain so sharply defined as I do when the enlarger is used in the point light source mode. It is really an eye opening experience for me.
I have, as many others have too, I am sure, heard so many things over the years about different light sources. I have found it really interesting and informative to try the different types of light output.
I meant this as a report for those who have questions about the effects of the various sources and having wondered about them or not had availability to determine the differences. No other purpose should be assigned to this post.
Donald, is the 1,000w bulb a conventional long-tube type, similar to a work lamp bulb? Did you design a parabolic refelctor, or were you able to adapt a readily available refelector to suit your needs? How did you deal with the heat output from this light source? Seems like you could fry an egg on the housing after a while with 1,000 watts flowing through the lamp.
How does the "point light" source differ from a conventional condenser enlarger? I have no background in physics, so a layman's explanation would be helpful.
Finally, could you take an image and enlarge it using the various methods at your disposal by way of an example? I still use an old D5-XL with a color head, but would be interested in anything which makes for a sharper print. Thanks, tim
FWIW on that auction site there is the Pulse Xenon system.
Donald , is this retrofit somewhat like the unit Jens has on the market??
How does the point light source work with your retrofit??
Originally Posted by noseoil
Thanks for your response. You pose very good questions. I will try to answer your questions in the order that you posed them
No, This is a bipin type lamp and not a long tube double ended lamp. The reflector design is not parabolic since a parabola would tend to do the opposite of what is needed in this case. I was not able to utilize an existing reflector. The reflector that I ended up using is a shape that incorporates both convex and concave forms in the design. I designed the shape and then built the reflector.
To deal with the heat, I utilize a blower to cool the lamp house. I have measured the lamphouse internal temperatures using a highly accurate digital thermometer. The maximum temperatures that I have recorded have been 135 degrees after one minute and thirty seconds of exposure time. This is a very unlikely exposure scenario since a typical print exposure would be twenty seconds at F16 for a 16X20 print from a 4X5 negative. Typical 8X10 enlargemens from a 4X5 negative are 8 seconds at F22. Needless to say, this is very fast when compared to the 250 watt lamp that I had used to this point.
By contrast without using a blower, I have cracked and melted glass with this lamp since it operates at 500 degrees celcius.
I will now try to explain the difference that a point light source provides. I will illustrate this by saying that the smaller the source of light in relation to the object that it is lighting, the higher the contrast between shadow and highlight of the lit object. To illustrate, if we take the sun in relation to the earth on a clear sunlit day, we notice that we have very distinctly formed shadows. However conversely if we examine a day when we have a cloud cover, the shadows are not well formed or distinct. The reason is that the clouds have had the effect of transforming the relative small light source (the sun) into a larger light source (the backlit clouds). A point light source more closely replicates the effect of the sun in the example above. All other light sources are some form of the cloud covered sky in vary degrees of thickness of cloud cover. The most diffuse would be the cold light source or the diffusion light source used in varible contrast enlargers or color enlargers. The less diffuse would be the condenser enlarger using a frosted lamp such as the Thorn lamp that had been commonly used in the Durst enlarger that I have.
All point light sources would be used with condenser enlargers since the desired effect is obtained by using a small light source with an optic system that serves to collimate and focus the light at the nodal point of the enlarging lens.
In regards to providing images, I am sorry that I don't own a digital camera and my scanner is on the blitz right now. I will say that images would probably not provide help to you since each manufactures lamp house would entail different and specific design criteria.
I hope that this answers your questions. If I have failed to explain myself completely please feel free to ask followup questions.
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Originally Posted by Bob Carnie
In some respects my retrofit does resemble the one that Jens has on market. It differs in some notable ways, however. The point light source provides the sharpest prints that I have ever made. It provides well defined tonal delineation and improved local and micro contrast.
As in all things there are exchanges to be made. The exchange for increased sharpness has been an increase in spotting.
Donald, thanks for your detailed explanation. It sounds like a print made in this manner would be similar to a contact print, in that the light does not have as much of a chance to "scatter" due to the relatively short distance between the film's image and the paper's emulsion.
I can see where you would have better sharpness with this procedure. I guess a print made from a minimal agitation or stand developed sheet of film would be very nice to look at. Perhaps as close to a 3D effect as is possible with a two dimensional image. Best, tim