Enlarger too bright (Durst CLS450)

[Sirius Glass]

The problem that the OP, henpe, has asked us about is short exposure at f8/11 so what is wrong is the short exposure at these apertures.
He hasn't exactly said which of the two he uses(f8 or f11) and he mentions a few seconds rather than an actual number but let's say his few seconds is 3 and his min aperture he currently uses is f11 then f22 is only 12 secs. Still quite short for any dodging and burning. On that basis f32 is really the first f stop that is comfortable for relaxed dodging and burning. Unfortunately even f22 gives concerns over diffusion and presumably f32 is well over the last safe aperture to avoid diffusion so as a solution is dismissed.

So sticking to the problem mentioned in henpe's post it looks like he needs to stop at f16 and use "work-arounds" such as extra neutral colour filtration or add ND into the filter drawer, doesn't he?

pentaxuser

Yes. Add equal parts of cyan, yellow and magenta to form a neutral density filter.

 

[pentaxuser]

I do those sort of enlargements on a routine basis without trouble using an Ilford MG500 head (2x300w) - it should be easier for you with over a stop less power! Remember that a 3x enlargement allowing for 8lp/mm on paper only needs 24lp/mm on the film (in a lossless system, but the losses are not too drastic, especially not in a relatively small enlargement - and stopping to f16 or even 22 should be fine).

Good luck

Laclan, can I ask what your exposures are with 600W and f11 and what you use to lengthen the exposure to the kind of range that henpe's needs, namely about, say, 15-20 secs.

If you achieve what henpe's needs to achieve but using double the power then I remain puzzled at why his system cannot achieve 15-20 secs exposures

I am simply trying to get the the bottom of what is going wrong in henpe's set-up from an investigative point of view.

Before the thread takes off into another round of repeat of solutions involving "work-arounds" I appreciate that sticking to f11 to avoid diffusion and at the same time, achieving longer exposures may be solved from a practical aspect with neutral density and working with the controls already built-in with the enlarger extra Y,M and C may provide this most easily.

pentaxuser

 

[Lachlan Young]

Laclan, can I ask what your exposures are with 600W and f11 and what you use to lengthen the exposure to the kind of range that henpe's needs, namely about, say, 15-20 secs.

If you achieve what henpe's needs to achieve but using double the power then I remain puzzled at why his system cannot achieve 15-20 secs exposures

I am simply trying to get the the bottom of what is going wrong in henpe's set-up from an investigative point of view.

Before the thread takes off into another round of repeat of solutions involving "work-arounds" I appreciate that sticking to f11 to avoid diffusion and at the same time, achieving longer exposures may be solved from a practical aspect with neutral density and working with the controls already built-in with the enlarger extra Y,M and C may provide this most easily.

pentaxuser

f16, sometimes f22 & a baseline aim of 11-16s exposure. You're unlikely to notice diffraction issues on the 3x enlargement in question unless you were (for example) making separations on to film. In that case you'd possibly be using different lenses & preferably a shutter for maximising consistency. A 150mm might make a difference too - a 10% longer focal length will help. Remember that the results found by Ctein regarding optimal apertures under test conditions (to take one case) might only have tangential relationships to reality/ actual practice. The OP should do his own testing & see how his system performs at those apertures. He might find that theory does not bear out in practice, especially given the limited resolving power of most papers and the small enlargement in question. We're not talking about a 30x enlargement off 35mm here.

I do wonder if the dichroic filters etc may be fading somewhat in the CLS, but other than that, dozens, if not hundreds or even thousands of photographers relied on those heads to produce first rate results on papers that were just as fast.

 

[pentaxuser]

Thanks, Lachlan. On balance my take from your posts and the thread overall is that f16 may be necessary and is quite safe and if henpe requires even more exposure then some form of added ND will be enough and as has been said added Y,M and C will do the trick

pentaxuser

 

[Luis-F-S]

Go to f/16-f22 which will increase your exposure to 8-16 sec, and if neede use a 180 mm lens! L

 

[MattKing]

Remember that diffraction is a function of the physical size of the aperture, not the effective f/stop.
f/16 involves a physically smaller aperture in a 50mm lens than it does in a 135mm lens. So a 50mm lens set to f/16 will suffer more from diffraction than a 135mm lens set to f/16.

 

[darkroommike]

One of the many lovely things about Durst color heads is that the filtration is in density units, not CC or CP values, hence 30C+30M+30Y=30ND which is a 50% reduction in light output one stop. 60-60-60 is two stops, etc.

 

[hacked - sepiareverb]

Oriental Seagull VC Warmtone is a slower paper than the Ilford Classic.

 

[ac12]

Is there a bulb smaller than 200w? I figure you need to drop the wattage significantly to make a decent difference in light output.
I had the same problem with my M600. The stock 150w bulb gave me exposure times too short to dodge/burn, less than 5 sec. I went to a 75w PH-211, which was better. I would have preferred to go down even further, but they don't make a photo bulb lower than 75w, that I could find at the time.

Another option, if you can't find a smaller bulb, is a glass screw on the lens ND filter.
The glass ND filter should be a decent enough optical quality that it won't affect the image. IOW, not the $5 junk box filters.

 

[CMoore]

A different brand, but if i am reading your OP correctly.......i had a similar problem.

https://www.photrio.com/forum/threads/beseler-diffusion-chamber.155695/

 

[jim10219]

I've got a similar problem myself. A Beseler 23c, Ilford MG IV Fiber based paper, Ilford MG filters, and with either a 50mm or 105mm lens, I'm getting exposure times around 4 seconds at f/11 with a standard density negative. I bought my enlarger used, and only have the one bulb for it. It's unmarked, but it looks like a PH140 75w bulb, if I were to guess. I've long suspected it maybe wasn't what it was labeled. Either that or my filters are old or there's something wrong with my paper.

In any case, I took a piece of translucent white plastic and cut it to size and placed it in the filter carrier above the condenser head. It cuts down the light enough to make times manageable.

 

[darkroommike]

Is there a bulb smaller than 200w? I figure you need to drop the wattage significantly to make a decent difference in light output.
I had the same problem with my M600. The stock 150w bulb gave me exposure times too short to dodge/burn, less than 5 sec. I went to a 75w PH-211, which was better. I would have preferred to go down even further, but they don't make a photo bulb lower than 75w, that I could find at the time.

Another option, if you can't find a smaller bulb, is a glass screw on the lens ND filter.
The glass ND filter should be a decent enough optical quality that it won't affect the image. IOW, not the $5 junk box filters.

The standard bulb for the Durst M600 is 75watts not 150watts.

 

[darkroommike]

I've got a similar problem myself. A Beseler 23c, Ilford MG IV Fiber based paper, Ilford MG filters, and with either a 50mm or 105mm lens, I'm getting exposure times around 4 seconds at f/11 with a standard density negative. I bought my enlarger used, and only have the one bulb for it. It's unmarked, but it looks like a PH140 75w bulb, if I were to guess. I've long suspected it maybe wasn't what it was labeled. Either that or my filters are old or there's something wrong with my paper.

In any case, I took a piece of translucent white plastic and cut it to size and placed it in the filter carrier above the condenser head. It cuts down the light enough to make times manageable.

Have the same problem with the school enlargers and bought some Rosco ND theatrical gel.

 

[henpe]

In any case, I took a piece of translucent white plastic and cut it to size and placed it in the filter carrier above the condenser head. It cuts down the light enough to make times manageable.

Yeah, I have tried a similar approach and installed a cheap acrylic ND-filter, but above the mixing chamber, it melted.... But this is I good idea nevertheless. I will now go with a frosted piece of glass instead, I've figured it will reduce light by ½-a-stop. (On the CLS450, there is a perfect slot for installing a sheet of "filter" above the mixing-box, but no filter-drawer or equivalent below the box, that's why I am so stubborn about putting things above the box, even though there is a heat problem)

Regards
Henrik

 

[Johnkpap]

Hi Henrik, Your latest post reminded me of something that also may help

My Durst L1200 was originally owned by a government agency called the Dept of Transport here in sunny Australia. I bought it many years ago it came with 2 heads and everything in its original box in like new condition. My FEMOBOX 450 N came with 2 lower diffusers
One is labled Dif 1 the other is labled Dif 2 the id is on the long edge in small print.
Dif 2 is twice as thick as Dif1

Please check your FEMOBOX and see which one is fitted

If you have a Dif 1 you can make a Dif 2 by cutting a bit of Perspex Plastic the same approx 5mm shorter and tape it in place with Scotch Magic tape

Johnkpap

 

[ac12]

The standard bulb for the Durst M600 is 75watts not 150watts.

M600 manual states 60-150w.
Mine was bought NEW with a 150w bulb, which I quickly replaced with a 75w bulb.
But this was well over 40 years ago, so I do not remember if the dealer put the 150w bulb into the box, or if it came from Durst with the 150w bulb.

 

[henpe]

Please check your FEMOBOX and see which one is fitted
Johnkpap

Hi Johnkpap! Great advice! I will check upon this next time I am in the darkroom. Even though it seems I should be able to find a label on the diffuser, just for reference, do you remember how thick Dif 1 and Dif 2 are, approximately?

 

[Johnkpap]

Hi Henrik,
The Dif 1 is approx 3 mm thick Dif 2 is approx 6mm thick and is beveled so that it is 3mm thick on each end for the first 5 mm and can fit in place of the Dif 1

Johnkpap