I did the same using my G139 with a Ilford 500 head in condensor-version (like the LAVAKO, it sat on top of the condensor housing) and the CLS1000.
Originally Posted by Donald Miller
Sorry, no visible difference in local contrast... I sold the Ilford/condensor head and kept the CLS1000.
I compared a Durst L54 to a Durst L1000 with CLS450 using the same paper, developer, lens and the correct condenser set on the L54. As both enlargers use the same lensboards and carriers comparing involved just swapping the carrier with a 35mm negative and the lens together with the lensboard. After adjusting for contrast both light source were easy to tell apart as slightest negative defects were visible on the negative from the condenser enlarger. There was no gain in sharpness with the condenser.
There appears to be at least one more option out there for lamps in the point source format.
The enlargers John got included one that was fitted out with a GE BHD lamp, which is a 20V, 100W point source lamp (reprographic lamp). Looking online, they don't appear to be expensive lamps at all. I'm not sure exactly how it works yet, as I don't have a 120-20V transformer to try it with, but it appears it may be a viable option to the $800 point source that is offerece by Jensen.
I'm going to see if I can track down a transformer and try it out as a point source enlarger.
Also note that the Durst instructions indicate that the enlarger should be operated AT FULL APERTURE for point source enlargement. I'm not sure why this is, other than the possibility that the lenses are sharper at full open aperture. They recommend stopping down 2-3 stops for the OPAL lamps, as expected. I was suprised by the full aperture statement in the manuals.
Originally Posted by skahde
Well obviously I will not contend that your test results are erroneous. But I will go on to say that you are not using the same enlarger that I am using. That may explain a portion of the difference in your test results. Additionally a 35 mm negative is not the same thing as a 4X5 or 5X7 negative. A 35 mm negative or medium format negative will not contain nearly the density information that a large format negative contains. So it is highly likely that if the information isn't there in the first place it wouldn't be able to be represented with any enlarger.
As is often the case, apples and oranges when compared do not taste or look the same. I would suggest that you may want to give more thought to your position in the future considering the full impact of what is being discussed. In this case that happens to be the Durst 138S enlarger. That happens to be a 5X7 condensor enlarger.
On a separate note responding to another post, the 138S and the 139 while obstensibly the same in many respects did not originate with the Ilford light source. Mine does not use this light source. I have previously explained why I wouldn't consider that light sourse as an option so I see no need to reitterate what I have already stated. However as I have stated before apples and oranges are not the same.
I have read the Durst instruction also but my interpretation is different. I recall them saying that used wide open the point light source will give sharper prints than using a lens stopped down with other light sorces. They also caution one that if the lens is stopped down to much you will bring anti newton rings into focus. Depending upon just how small the lamp filament and its distance from the lens will determine the amount of coverage. If a lamp such as the Pulam is use at a distance sufficient to just barely fill the lens nodal the maximum effect of the point light is reached. When this happens any change in magnification will require a change in lamp position because vignetting will occur. This is probably going to change with aperture also. I have NOT used the Pulam lamp.
I have the older Durst point light source using the GE 20 volt lamp and the transformer in a Durst S45..a varient of the 138 I am using it with a 63mm N 2.8 El Nikkor usually.at approximately 6.5x magnification. At a setting that maximizes its point light capability the lens with the proscribed condenser set is no where near just barely filling the enlarging lens nodal...it covers more. While this may not maximize the greatest possible point light sorce condition it certainly is a brilliant and contrasty system. It is much different than using a large diffused bulb with with condensers. I imagine the reason the GE 20 Volt lamp lamp does not reach the maximum the effect possible is due to the filament size. If I remember correctly the Pulam has a 4mm filament the GE filament is larger. There is no problem using the Enlarging lens in a stopped down a couple of stops and you will see an improvement as the lens reaches it optimum setting..
When you first use a point light source with a focussing magnifier the view of the negastive is vastly different even just while focussing. The requirement for cleanliness so that print spotting is not necessary is extremely high. At the same time if you have a negative with extreme detail that is properly exposed and developed for point light source printing on a number 2 or 3 paper the sharpness will be outstanding. I believe that this is a condition where having an oil immersion carrier can be very helpful...I have a Condit oil immersion carrier.
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Originally Posted by Michael Mutmansky
Thanks for this information. Please let me know how this works out. My primary concern is the wattage of the lamp. Full aperture would certainly help the smaller wattage, I just wonder if it will be enough.
I noticed that Jensen has recommended full aperture enlarging for some time with the Durst equipment he sells. Obviously very precise alignment will be required. Again, thank you.
Do you have a Durst transformer for the GE lamp? I'm wondering what voltage the output side produces. It could be 20V, or it could be 19 or 19.5 to increase the lamp life a bit.
I figure I can get a multi-tap choke transformer with taps for several voltages at about the correct (20V) output, and then try it out for not too much expense.
I have a drum scanner, sio I have mounting oil here, and I also have mounting gel. I suspect I could use mounting gel with the normal glass carriers without causing a mess, as it is quite thick. I had intended to try that.
Is there any point in getting the proper glassless negative carriers for 4x5? I could see some benefit to using a glassless carrier with an OPAL lamp for faster printing and possibly for less critical work.
Are there any sources for the negative carrier glass out there, other than new-old-stock? I'd like to consider getting some AN glass for the top sheet.
The full aperture mode that Jensen advocates seemed to be mostly tied to production logistics, but apparently the best working aperture for a lens may well be very close to the maximum aperture. As long as the lens is long enough to fully cover the film at full aperture satisfactorally, I suppose it would be best working at that aperture.
I can't see how people do dodging and burning with real short exposures, as there isn't any time to get the mask into the proper position and suitably feathered before the exposure is completed.
Donald, are you using a point light source with the Latico xxxT coated condensers? I wonder if there is any significant benefit from using the coated condensers as these are really rare. I got the Durst point-light source transformer (it says Durst USA, Garden Hills, NY.) with my L138 and the GE bulb with non coated condensers. I wonder if the coated condensers are worth getting. It is possible that the lack of flare within the condensers will lead to even sharper and cleaner prints.
I have heard of the results where Ctein and others have made the claim that properly adjusted for, there is no difference between diffused and condenser light sources. And for years, I have wondered about the veracity of these claims. To begin with, what is the quality of the condensers used in those tests? Durst condensers use really top grade optical quality water-white glass. Compare a Durst condenser to one from Omega or Beseler and you can see the difference.
Second, the opal lamp based condenser heads are actually semi-diffused light sources due to the large globe of the opal lamp. True condensers will use point light sources.
I agree with Donald as I see improved local contrast and separation of tones with my own work. But I am from being rigorous and scientific so take this as an anecdote, please.
Yes, I have the Durst transformer. I do not know the maximum voltage since I do not have a voltmeter...which is stated as being 20 volts. This is a variable voltage transformer going in a stepless fashion from maxiumum to nothing with 10 marked steps I am normaly using it a F4-5.6 for 10-20 seconds with a 6.5x magnification with the transformer set at number 5 to 6. I believe that this transformer marked Vairipoint is not an item designed by the factory engineers since it says on the unit "developed and marketed by Durst (USA)."
I have not used a meter to determine how much difference each step is but it seems to be in the range of 1 stop, certainly each step is a significant change.
I have Kami fluid as well as oil. I do not have experience with the gel. I believe it would work. The major benefit of glass is flatness. If you can achieve a very high degree of flatness with an open frame carrier, such that using glass makes no improvement then that would be great. It is something I have never been able to achieve at optimum lens apertures. Much of my photography is of city scenes and has fine detail in the negative corners. I have tried many different ways of getting a negative to be flat in an open frame carrier and I have never been sucessful
One approch that will work nicely is in the case of the Nega138 carrier is to use an open frome on the bottom cut out to the negative size..I am referring to the Durst bottom here not homemade and glass top. This can give a high degree of flatness. For 35mm and 6x7 I have used the appropriate Durst open frame bottom piece and a piece of anti newton glass from 6x7 glass slide holders.
For usage w/o anti newton glass I bougth several cut pieces of Denglass to fit my Condit carrier...this glass is approximately 5mm thick.. 4 pieces for top and for the bottom....4 pieces 3 7/16"x3 7/16"...4 pieces 5"x5" I bought the pieces cut to my specifications from the Maryland Glassworks. The price including shipping was $43.00 The cutting and edge smoothling were very nicely done. The service was very good. I am sure that if you wanted pieces cut to fit the Neg138 carrier that one 2 pieces each for top and bottom would be similar in total.
This Denglass is coated on both sides and will allow a big reduction, not neccesarily an elimination of Newton rings. Obviously this will be determined byt the flatness of the film stock being used as well as the prevailing humdity.
Donald, our reasoning may be closer than you think. Taking another look at my first post you may find that I suggested to do your own testing before making a decision. After you said you already did so I tried to make clear, that the result of this comparison may differ, not that your results - which I respect - are questionable and I was well aware that the difference in format may well account for most of this difference when I mentioned it. My apologies for not stating this explicitly.
Originally Posted by Donald Miller
As long as we are discussing what works for each other, we aren't using objective measures anyway. If you like what you see and your customer agree, more power to you.
Last edited by skahde; 06-08-2005 at 12:39 PM. Click to view previous post history.
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