Bulb halogen of Durst M605 too much bright

bdial said:

A neutral density filter on the lens is probably the easiest solution, if you don’t want to reduce the exposure time any further.

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Craig75 said:

If its a colourhead and black and white film you can add a load of cyan filtration too

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ic-racer said:

Only makes it darker to your eye. The paper can't see the red the filter blocks unless it is a poor wide band filter that blocks some green.

A metal scrim between the lamp and the mixing box is sometimes the safest option. It won't burn, break, fade or change the color of the light.

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Craig75 said:

Ah ive always seen it mentioned you can use cyan to speed match multigrades.

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InExperience said:

Dear all,

Last my session of darkroom I encounter an issue. Because the film is high contrasted, I set f/16 on the lens enlarger but I got time to print around 8 seconds as well by 6x6 lever. It's too brief.

My bulb halogen is as suggested 12V 100W, I tried to change with a new one of 12V 75W but I discovered that luminosity is the same, in fact I have the same issue.

What lamp or what else do you recommend to extend my time of exposure?

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pentaxuser said:

From the part of your enlarger you have shown us it looks like a B&W condenser diffuser so not a colour head one? These don't have halogen bulbs. Does your enlarger have a colour head. It doesn't look like it. What does your bulb look like and how does it fit. Is it like a normal bulb or a flat faced one with two male spikes at its end that fit into a female ceramic holder?

Can you help me to be sure if it is a colour head or a B&W enlarger before I make further comments. All I will say is at this point is that dropping the wattage to 75W from 100W does change the light intensity. That the laws of light so if there is genuinely no change in light intensity when you use a 75W then something else has to be wrong

Thanks

pentaxuser

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ic-racer said:

A metal scrim between the lamp and the mixing box is sometimes the safest option. It won't burn, break, fade or change the color of the light.

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ic-racer said:

Only makes it darker to your eye. The paper can't see the red the filter blocks unless it is a poor wide band filter that blocks some green.

A metal scrim between the lamp and the mixing box is sometimes the safest option. It won't burn, break, fade or change the color of the light.

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ic-racer said:

Never. Yellow + Magenta makes Red, which, of course the paper can't see and is the "Neutral Density" in the eye of the paper. The Cyan does nothing for orthochromatic emulsions, unless it is a poor filter that has some effect on green (and some do, you might get a slight lightening of a print, but it is an abnormal response).

Here is another way to see for one's self. Project white light, swing the red filter in place (under the lens) for focusing. Now activate the Cyan filter. What happens, the baseboard goes black. So how does the paper respond to that? No change because it was not seeing the red in the first place. The Cyan only made it darker to your eye.

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pentaxuser said:

Thanks, InExperience for clarifying matters. I too have a 75W bulb in a colour head and it definitely reduced the light output and increased the exposure compared to my former 100W bulb. Are these small prints such as 5x7 or smaller? Without any filters at all such as Ilford MG filters or the colour filters in the colour head and if I am doing a 5x7 print then I might have 8 seconds at F11 but once I use either MG filters or dichroic head's filters then this rises by a few seconds and then doubles at F16 so I am puzzled as to why your exposure will not go above 8 seconds.

Do you normally get acceptable exposures with other negatives and this set of negatives are the exception because they are thin negatives?

pentaxuser

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InExperience said:

Thank you pentaxuser.

I used to print on paper 9.5x12in, moving only the magenta filter on the head. If for example M=30 Y=0 C=0 and shift all the value +20 then M=50 Y=20 C=20 now the frame is less bright than the prior (only M=30). It could be a good escamotage to test the time of exposition.

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MattKing said:

I've experimented with replacing that exact bulb with a 5000K 50 watt equivalent LED bulb in my variable contrast head LPL 7700 enlarger. Using the 135 carrier, that bulb reduces the light output by a factor of eight - 3 stops - compared to using the manufacturer specified EFP halogen bulb.
With the LED bulb I used, the contrast control response isn't as linear as with the halogen bulb, and it may give less range - I have to do more tests, because the speed matching goes out the window.
The reduction in intensity is actually a problem when using the LED bulb with the 135 carrier and film - exposure times are too long. Exposure times are better with larger negatives. The LPL enlarger only offers a single choice for a light diffuser, whic covers 6x7.
The positives are:
1) the LED bulbs are cheap - my 6 pack of bulbs cost me $22.00 CDN shipped;
2) the LED bulbs are available at stores that carry household lighting bulbs;
3) the LED bulb runs very cool - the enlarger doesn't seem to heat up at all; and
4) the projected life of the LED bulbs is much, much longer - I probably have 30+ years of bulbs in that 6 pack!
There are 75 watt equivalent versions of those LED bulbs, but they are about 4 times as expensive - too expensive for experimenting.
There may also be different versions of those LED bulbs - different beam angle and different light colour - that would work better.
I'll probably go back to the halogen bulbs for the forseeable future. The LED bulbs will be available as emergency backups.
For clarity, the LED bulbs would not be good for colour printing.

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wiltw said:

Use 2700K LED...the output light is all at the same end of the spectrum as the original halogen.

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pentaxuser said:

InExperience., it looks like your solution should work OK. although I am still surprised that at a print size of 9.5x12 the exposure hasn't increased to more than 8 seconds.

I had a quick search for 50W enlarger lamps with the right 2 prong fitting for the Durst but couldn't find any that were less than 75W so you may be stuck with using your additional neutral filtration method.

pentaxuser

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InExperience said:

I let you know after Friday afternoon when I will try to print using my method, otherwise I will consider to buy neutral filters.
Thank you.

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