Does VC paper require 3000k light source from enlarger?

MattKing said:

Ralph is an acknowledged expert with one of the best books in the market on darkroom work. However, since his serious heath problems, he has difficulty typing. You shouldn't mistake brevity for snark - I am sure that he didn't mean to offend.

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Sorry, the wording sounded sarcastic. My mistake & I apologize.

The less experience, the more problems to invent. I'd use what the Durst manual recommends and be done with it. They probably know a thing or two as does Ralph! None of the 5 enlargers I own use a 3000K bulb. They're all slightly less.

durst didnt have access to cheap light emitting diodes, but I get your point. It was mostly for heat and convenience reasons but l will do it right before doing it "wrong".

kingbuzzie said:

durst didnt have access to cheap light emitting diodes, but I get your point. It was mostly for heat and convenience reasons but l will do it right before doing it "wrong".

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+1!!!!!

To add a bit of past information regarding light source and its effect on variable contrast papers, here is some information regarding filter sets offered back in 1959 about Ilford Multigrade:

"5 Filters, marked 1-5, with filters 1 and 2 being magenta coloured (lowest contrast) and filters 3, 4 and 5 being increasing shades of yellow (and increasingly hard contrast).
In fact there were 7 Filters available at this time, but intended to be sold as 3 different sets of 5 Filters; one set (Filters 1-5) for enlargers with tungsten filament lamps, one set (Filters 2-6) for contact printers with tungsten filament lamps and one set (Filters 3-7) for enlargers with white cold-cathode lighting."

and then in the 1980s
"11 Filters. Filters numbered 0, ½, 1, 1½, 2, 2½, 3, 3½, 4, 4½, 5. Filter 0 is an amber straw colour, with higher contrast filters becoming magenta and blue."

tezzasmall said:

I first started with a Paterson 35mm enlarger at home that took a florescent light. I don't know where that lies on the colour temperature scale?

Terry S

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Thinking back, the Paterson enlarger operated in a different way to others, in that the light was ALWAYS on and a shutter opened and closed to let the light onto the easel / paper. This was due I think, to the lights of the time used taking a second or two to come to full brightness. I'm not sure if you have to take this into account with modern LED lights or whether they do give full brightness straightaway? I mention this for in enlarging a second or two can make a big difference to exposures.

Terry S

White LED's are not truly white, they appear white by two different approaches, the first is to use LED's emitting several different colors of light, which may of may not be a good match for your VC papers or they hit a phosphor with a UV LED that then emits "white" light.

Here's a link to a J.B. Harlin article, He made a VC lamphouse using blue and green LED's and a controller but it's hardly a screw in substitute for a standard lamp. http://www.jbhphoto.com/wp-content/uploads/2015/01/LEDsVCPrinting03.pdf

Someone also makes a drop in replacement LED lamphouse for the Omega
D2. http://www.modernenlargerlamps.com/Modern_Enlarger_Lamps/Model_1a.html

And refresh my memory, does the M606 use a reflex lamphouse like the other Durst 6x6's? With a mirror? If so your negative is being illuminated by the side of the lamp, not the top. LED's are directional, most of the light coming out of the top of the lamp whereas an incandescent bulb illuminates efficiently with the light coming off the side of the lamp.

One other thing, hard to believe, but bright LED's run hot, not incandescent lamp hot but hot, I have LED lamps that warn against using the lamp inside a fully enclosed lumiere (lamphouse).

I'd stick with a 211 lamp myself, I also have about six spares in a box, never know when a lamp will blow. I also have spares for other enlargers using other lamps.

tezzasmall said:

I'm not sure if you have to take this into account with modern LED lights or whether they do give full brightness straightaway?

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There is no "ramp up" with LEDs.
They come on at full brilliance instantly, as soon as operating voltage is present. .

However, this assumes the DC operating voltage is always available and is just switched on and off like a wall switch.
If you're actually switching power to the AC/DC supply that powers the LED, there would be a delay.

- Leigh

I made a light source with a 3K LED ceiling lamp from RONA. (Lowes in the US).

The exposure time on grade 5 is two stops longer as compared to a tungsten lamp. This is due to the different spectrum. I believe LED white lamps are poor in green energy.

Kilgallb said:

I made a light source with a 3K LED ceiling lamp from RONA. (Lowes in the US).
The exposure time on grade 5 is two stops longer as compared to a tungsten lamp. This is due to the different spectrum. I believe LED white lamps are poor in green energy.

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Real LEDs are very monochromatic.
You can get RED, GREEN, or BLUE LEDs, each emitting only the single color described.
To make an enlarger head you would need to use one GREEN and one BLUE LED, with amplitude control of each.

Using any kind of WHITE emitter is a crap shoot unless you know its spectral characteristics.
As mentioned earlier, there are two ways of making "white" LEDs.

- Leigh

Kilgallb said:

I made a light source with a 3K LED ceiling lamp from RONA. (Lowes in the US).

The exposure time on grade 5 is two stops longer as compared to a tungsten lamp. This is due to the different spectrum. I believe LED white lamps are poor in green energy.

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Was this a lamp intended to replace a dichroic halogen lamp?

Just an observation -- the dichroic "tungsten" lamp used on enlargers (typically color heads like Durst color heads) is actually a Xenon lamp which is far brighter than a common celiling dichroic lamp. For example a 100W dichroic lamp specific for this application (i.e. Osram HLX Xenophot) will be far brighter than an equivalent 100W halogen lamp, not to mention a 50W ceiling halogen lamp.

The LED ceiling lamps i've seen are intended to replace the 50W halogen dichro lamps, and thus all of them will have inferior light output to an enlarger dichro lamp. So, my point is that the reason you need more exposure time, might be simply because of lower light output in general.

As for the condenser enlargers that use the classic opal bulbs, (i.e. 100W opal bulb) these opal bulbs are also photo-specific (i.e. Philips Photocrescenta bulbs), they have life ratings of only 100 hours which make me think they are "overvoltaged", and thus will give much more light than an equivalent 'household' tungsten bulb (i.e. 100W tungsten bulb). Thus a LED bulb said to be "equivalent to a 100W tungsten bulb won't match the light output of the opal bulb. And, as mentioned, it might not radiate light omnidirectionally, as the real opal lamp.

Dan0001 said:

If your experimenting with a LED bulb becuase of a concern for overheating the negative I think a tungsten 75 watt bulb in a Durst 606 would not be a problem-they distribute heat well. Bear in mind even if the negative stage is warm or hot the glass negative carrier(the most common one) would prevent negative popping. If your doing this to save money on electricity, the amount would be miniscule. If your doing this just for the hell of it, go for it. My guess is that you will go back to the original recommendation of a tungsten opal bulb. Just my two cents.

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+1

Also, if the LED light source is strong towards the blue-UV part of the spectrum, it theoretically could cause less sharpness, since the papers are sensitive to that spectrum of light (i think VC papers are also sensitive to a part of the UV spectrum). Tungsten lights are very low on UV content and blue content; cool white LEDs are high on blue content and some can have UV content as well.

Since enlarger lenses are usually not apochromatic, this means that extreme blue and UV light will focus on a different plane.

This is just a theoretical consideration. All in all, the opal bulb is cheap, nice, beautiful, and is what your enlarger craves...

Leigh B said:

There is no "ramp up" with LEDs.
They come on at full brilliance instantly, as soon as operating voltage is present. .

However, this assumes the DC operating voltage is always available and is just switched on and off like a wall switch.
If you're actually switching power to the AC/DC supply that powers the LED, there would be a delay.

- Leigh

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I have replaced all incandescent bulbs in my house with LED bulbs from IKEA. They are all instant-on, but some of the older ones have a very noticeable fade-out when switched off - on the order of a second. The newer bulbs seem to be instant-off to my eye.

Let's not lose sight of the fact that the original question was about the ideal color temperature for black-and-white printing.

The answer depends on what kind of paper one uses. Obviously, graded papers are not nearly as sensitive to changes in the color temperature (or spectral power distribution for non-black-body sources) as long as there is enough blue light in the source to expose the paper in a reasonable time. The original "cold-light" heads from Omega and others just used "conventional" circular fluorescent bulbs and assumed graded paper was being used. Older Aristo grids were similar, and were not optimized for use with VC papers.

Modern VC papers seem to be optimized for use with tungsten/tungsten-halogen light sources. This from Ilford about their Multigrade papers:

"MULTIGRADE papers are designed for use with most enlargers and printers, that is, those fitted with either a tungsten or tungsten halogen light source. They are also suitable for use with cold cathode (cold light) light sources designed for variable contrast papers.
Cold cathode enlarger heads
Enlargers fitted with a cold cathode (cold light) head which has been designed for use with variable contrast papers can give a full contrast range on MULTIGRADE papers.
However, although a full contrast range may be available, it might not be evenly spaced. Also, in some cases, a full contrast range may not be available – it depends on the cold cathode lamp used."

What is important is that there is a full range of blue and green light to which the paper is sensitive in a distribution that gives a grade spacing that is usable. Obviously, the spectral distribution that the paper is designed for is that of tungsten light. When using LEDs, etc., one should then strive to find a spectral power distribution in the blue and green range that approximates that of a tungsten source. Many solutions are possible; it's just an engineering problem. The easy way, however, is just to get a tungsten bulb...

Doremus

flavio81 said:

Was this a lamp intended to replace a dichroic halogen lamp?

Just an observation -- the dichroic "tungsten" lamp used on enlargers (typically color heads like Durst color heads) is actually a Xenon lamp which is far brighter than a common celiling dichroic lamp. For example a 100W dichroic lamp specific for this application (i.e. Osram HLX Xenophot) will be far brighter than an equivalent 100W halogen lamp, not to mention a 50W ceiling halogen lamp.

The LED ceiling lamps i've seen are intended to replace the 50W halogen dichro lamps, and thus all of them will have inferior light output to an enlarger dichro lamp. So, my point is that the reason you need more exposure time, might be simply because of lower light output in general.

As for the condenser enlargers that use the classic opal bulbs, (i.e. 100W opal bulb) these opal bulbs are also photo-specific (i.e. Philips Photocrescenta bulbs), they have life ratings of only 100 hours which make me think they are "overvoltaged", and thus will give much more light than an equivalent 'household' tungsten bulb (i.e. 100W tungsten bulb). Thus a LED bulb said to be "equivalent to a 100W tungsten bulb won't match the light output of the opal bulb. And, as mentioned, it might not radiate light omnidirectionally, as the real opal lamp.

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It replaced a Beseler dichroic but I only used it for split grade monochrome printing. I left the filters out and used under the lens ilford filters as moving the dichroic settings jiggled the head and caused blur.

Interestingly, the LED lamp behaves like a tungsten lamp with Kentmere paper but less so with Ilford.

Luis-F-S said:

The less experience, the more problems to invent. I'd use what the Durst manual recommends and be done with it. They probably know a thing or two as does Ralph! None of the 5 enlargers I own use a 3000K bulb. They're all slightly less.

Click to expand...

It is my understanding that tungsten enlarger bulbs have a color temperature of 2750K like most other non-photoflood tungsten bulbs. I have never heard of a 3000K enlarger bulb but 2750K is close enough to 3000K for, as we say, government work. Use the one called for in your Durst instruction book............Regards!