using a dimmer on an enlarger lamp (i.e., #211 lamp)

David Lyga · Jan 17, 2019

For years I have used a dimmer. This both GREATLY increases the life of the bulb (# 211) and serves to increase the unduly short exposure times from thin negatives which are projected onto small paper sizes.

My question is this: does the increased yellow (due to the under-running of the bulb) play havoc with contrast filters, or is this a rather moot point, given the fact that my under-running is only about 10%? Interesting question that probably has never been asked before. - David Lyga

glbeas · Jan 17, 2019

Its been asked before and it does have a small effect at 10% drop, maybe not easy to notice. If in doubt add a little filtration and see if the print looks better. It all boils down to what you have standardised on, if you get what you want out of it all is good.

Ian C · Jan 17, 2019

If you're using contrast filters with variable-contrast paper, how can it matter? Only light the same color as the filter passes through the filter to the paper. Other parts of the lamp’s spectrum are absorbed by the filter.

A small reduction in light intensity is expected, but is easily compensated for with a time increase, if necessary.

David Lyga · Jan 17, 2019

You know, I would think that the excess yellow 'influences' the actual filter, because I'll bet that a bit more than the filter color gets through. Interesting if others either concur with what I have said or agree with Ian C. Thank you. - David Lyga

DWThomas · Jan 17, 2019

I've not tried a dimmer -- I managed to equip myself with 50, 80 and 105 mm enlarging lenses that all take the same size filter and I use a two stop ND for small prints. There appears to be a color shift toward yellow as you dim tungsten lamps (the lack of which annoys me with dimmed LEDs for room lighting). The spectrum of tungsten lamps is continuous, so I would think as long as your settings remain consistent the results should be manageable. In the extreme, it might mean you could need a slight filtration tweak as you raise the head and crank up the brightness to go for a much larger print. I suspect in my normal workflow any such tweaking would disappear among many machinations in my normal path to a "finished" print.

voceumana · Jan 17, 2019

Dimming an incandescent bulb not only increases the warm end of the spectrum (reds, oranges, & yellows), it reduces the cool end of the spectrum (greens, blues, violets, and UV). It will shift the effective contrast of a variable contrast filter somewhat. The more you dim, the more the effect. You'll be able to see the results in your prints and make minor adjustments accordingly. It will make it more difficult to achieve the highest contrast. For thin negatives, that might not be a bad thing.

darkroommike · Jan 17, 2019

You could run a test with a step tablet.

tedr1 · Jan 17, 2019

About two years ago I asked myself this same question and directed my enquiry to Ilford's technical dept. This was the reply

"The Multigrade filter set was designed to work around 2856K tungsten illuminant but I am sure a reasonable change will only have a small effect on the contrast range. A large increase in col temp would shift all contrasts in the "harder" direction. You could compensate by using a 1/2 filter grade lower if necessary."

L Gebhardt · Jan 17, 2019

I tested this years ago with a variac and a step tablet. Running at 100V there was a very slight loss in contrast, well under 1/2 a grade if I remember correctly.

Loren Sattler · Jan 17, 2019

David, I also use a dimmer on my Focomat II for the same reason. I believe the standard bulb is 150 watts. That is way too much light for 5 x 7 inch RC prints exposed at f8. I adjust the dimmer to achieve exposure times of 10-20 seconds at an aperture of f8. I realize that I cannot rely on my notes for times to reprint a negative. But this is a minor inconvenience compared to other options. The Focomat II does not have a filter drawer where a ND filter could be utilized which would be ideal. For medium format I use an ND acetate filter when needed in the filter drawer of my Beseler 23C enlarger.

I have not noticed any issues with contrast with the dimmer but I am open to opinions. I have noticed that Ilford RC requires a 1/2-1 full grade higher contrast filter than Ilford Fiber Classic. Maybe the dimmer contributes to this some way?

David Lyga · Jan 18, 2019

DWThomas said:
There appears to be a color shift toward yellow as you dim tungsten lamps (the lack of which annoys me with dimmed LEDs for room lighting). The spectrum of tungsten lamps is continuous, so I would think as long as your settings remain consistent the results should be manageable.

You might get halogen lamps, instead, for your lack of yellow upon dimming.

When it was announced that tungsten bulbs would be discontinued I panicked because, at the time, the only replacements being touted were those nasty, non-dimming fluorescent bulbs. Everyone was having huge sales to get rid of tungsten stock and I went and bought 200 of the 100 watt bulbs.

NOW, we have halogen bulbs that, to me at least, are indistinguishable from their tungsten counterparts. I love them but cannot justify buying them because I have to use up the tungsten ones now that I bought them. But substituting halogen would be virtually no change, other than a slightly lower electric bill. - David Lyga

David Lyga · Jan 18, 2019

Loren Sattler said:
David, I also use a dimmer on my Focomat II for the same reason. I believe the standard bulb is 150 watts. That is way too much light for 5 x 7 inch RC prints exposed at f8. I adjust the dimmer to achieve exposure times of 10-20 seconds at an aperture of f8. I realize that I cannot rely on my notes for times to reprint a negative. But this is a minor inconvenience compared to other options. The Focomat II does not have a filter drawer where a ND filter could be utilized which would be ideal. For medium format I use an ND acetate filter when needed in the filter drawer of my Beseler 23C enlarger.

I have not noticed any issues with contrast with the dimmer but I am open to opinions. I have noticed that Ilford RC requires a 1/2-1 full grade higher contrast filter than Ilford Fiber Classic. Maybe the dimmer contributes to this some way?

I would advise you to ape the "David Lyga frugal method" when wanting to achieve repeatable, consistent results: Simply mark on the dimmer dial (with a Sharpie) the point that you will ALWAYS use the dimmer at. That way, you now have a standardized way to achieve the same amount of light each and every time.

Just because you are almost precisely one year older than me does not mean that you cannot learn from me.

I have noticed (maybe it is imagination) that achieving full grade 4 contrast, whilst the dimmer is dimming, is either difficult or impossible. Maybe that overly yellow lamp is saying something. - David Lyga

Jim Jones · Jan 18, 2019

I used a dimmer except while making exposures on my Omega B22 not only to extend life of an expensive lamp, but to reduce heat buildup in that hot running enlarger. At voltages probably well under 100 Volts, it was practical to leave the lamp on almost constantly. This eliminated negative popping.

Doremus Scudder · Jan 18, 2019

Don't obsess about it if you are getting the contrast range you need for printing. Sure, changing the color temperature of the light source will have a small effect on, e.g., Ilford Multigrade filters, since they are really just attenuating filters designed for a particular color-temperature range. Still, you can control the relative amounts of blue and green reaching your paper with them. Who cares if you need a #3 filter for your dimmed light and a #2 filter without dimming as long as you get the result you desire.

The only real problem would be with excessive dimming which would really reduce the blue component of the light source, making achieving higher contrast either impossible or time-consuming. In that case, you could simply un-dim your light source...

Best,

Doremus

Luis-F-S · Jan 18, 2019

I always used a dimmer when printing with my Durst 138S and original Durst bulbs which are almost impossible to find and expensive then. If the contrast shifts slightly just compensate with the filtration. With the Aristo D750 dimmer, I'm still on my first Durst bulb! Also used it with the Aristo D57 cold light head with a photo cell and a Metrolux timer.

Loren Sattler · Jan 20, 2019

Like the Durst, the Focomat bulbs are hard to find and worth extending their life. David, I use dots to mark my rheostat settings. One dot for 5 x 7 RC, two dots for fiber, etc. Not highly technical, but hey, it works.

Kilgallb · Jan 22, 2019

If you dim a halogen lamp you will get lower lamp life. The halogen cycle relies on tungsten exiting the filament then falling back. If you dim, there is not enough energy for the cycle to complete and the glass envelop blackens. This means energy (light and heat) cannot escape and the lamp burns out.

Pieter12 · Oct 16, 2021

If you have a filter drawer, ND gels are cheap and easy to use. Before getting an LED head for my D5, I used a 150W halogen bulb becuase it was smaller--a bit more like point-source--but brighter and hotter than the standard bulb. I had to tame it with heat-resistant glass and a selection of ND gels.

Paul Howell · Oct 16, 2021

Best bet to is hang out on Ebay until one pops up, may take a while. If you still have the condenser head use a standard LED bulb, not a true diffuser head, more like a semi condenser. I use a GE classic LED 1600 Lum which is about as bright as a 100 watt bulb. It works with VC paper to about grade 4 at which time I need to change to a tungsten enlarger bulb, as my negatives are scaled to print grade 2 it is not often that I print higher than grade 3.

using a dimmer on an enlarger lamp (i.e., #211 lamp)

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