Durst M605 Color Enlarger - 35mm Colour Negs -Exposure Problem
I had a problem in printing 5x7 RA4 prints from 35mm colour negs using the above enlarger. It came with a 100 watt lamp as specified by Durst. I should add for information that exposure is not a problem with 35mm B/W negs and B/W multigrade RC paper. Even at f16 which is the minimum on my 50mm lens I could not get an exposure long enough to register on my Paterson colour analyser which is calibrated to 4.5 secs minimum. I had to use a 80mm lens and /or the 6x6cm neg setting on the light box to get an exposure above 4.5 secs which is the lowest exposure that my colour analyser dial is calibrated for.
Using this combination the prints were fine but as the 80mm lens' largest aperture is 5.6 it made accurate focusing much harder than the would have been the case if I had been able to use a 50mm lens at f2.8 with the 35mm setting on the lightbox and it raised the question in my mind of what was the point of a 50mm lens for 35mm colour negs if I couldn't use it.
I noticed in previous threads this problem seemed to exist for others and that a number of solutions revolved around screwing a ND filter to the lens or possibly placing a ND filter under the lens. Neither solutions appealed to me although at least in the latter case a ND filter could be swung out of the way allowing maximum brightness for focusing.
However an alternative solution which has worked in my case was obtaining from a supplier a 75watt lamp which fits instead of the 100watt lamp specified by Durst.
Most negs will now print at usually f11 or occasionally at f8 using the 35mm light box setting and at exposures above 4.5 secs but which are still acceptably short. There is still enough aperture leeway for bigger prints at reasonable exposures without having to go down to f5.6 or less so middle range apertures can still be used. Again as I understand it, middle range apertures are technically better than those at either end. It also allows long enough exposures for occasional dodging. This still gives me the facility to use f2.8 for focusing at a light intensity which admittedly must be less than that for a 100 watt lamp but which is still very bright and mich better than f5.6 on my 80mm lens for up to 6x6cm negs.
I have had excellent service from Technical Lamps of Hampton, Middlesex UK who can supply these 75 watt lamps.
I appreciate that this supplier information does not help our non UK based members but the main point is that 75 watt lamps which fit the M605 do exist and provide a good solution to the problem.
If Durst specified a 100 watt lamp in its booklet which accompanies the M605 and if my problem of exposure is not unique to me then it begs the question of why Durst specified 100 watt lamps instead of 75 watt.
I can only think that when the M605 was being produced some 20 or more years ago RA4 paper was slower and needed 100 watt lamps for reasonable exposure times and secondly 100 watt lamps were or maybe still are needed for Ilfochrome paper and prints from colour transparencies which as I understand it require much longer exposures.
I'd appreciate any comments on this theory of mine about changes to RA4 paper from those members with more experience and technical know-how on enlargers.
For anyone experiencing this problem of too short exposures with 35mm negs I hope my thread helps.
I have the same enlarger and manage to get by with a 50 mm lens at f11 and the lightbox set to 66 when printing on Fuji CA. Quite possibly I have a weaker bulb.
If you still have a problem, dial in cyan filtration, then dial in an equal amount of magenta and yellow. Color should stay the same, but you have effectively added neutral density.
30 cc ea of c,m, and yellow will reduce light one stop.
Bulb brightness specified must be bright enough to make large prints at reasonably short times. The trade off is times for small prints can get short or you need to use small lens openings.