Advise needed: Looking for an additive filtration(Blue & Green) enlarger

mouren · Dec 23, 2010

Hi folks,

I am looking for a way to do additive filtration enlarging. I have been using this Aristo VCL head with Blue and Green twin tubes at the local lab, and I am loving it.

So, I started looking for an enlarger that will allow me to do Blue and Green split grade enlarging. And I feel like I am running in circles. Aristo doesn't seem to make VCL anymore, nor can I find any on-sale on ebay.

I did run across the Philip PSC enlargers, like the PSC 130 or the PSC 2000.

Are there any other choice? I think I would prefer not to do drop in filters, which as far as I can tell, won't give me an even spread of light.

Please help. after using the VCL head, I don't really want to go back to using the subtractive filtration system. I love the fine control I can get with the additive split grade system.

Thank you in advance.

jeroldharter · Dec 23, 2010

Just get a dichroic light source and use yellow and magenta instead of green and blue. For B&W printing it does not make much difference.

If you really like the cold light, you could buy a standard, used cold light and add below the lens filters (which will be yellow and magenta).

mouren · Dec 23, 2010

That would be subtractive, no?

I found that tends to clump up the blacks, while with Green & Blue, I can hit just 1 of the two emulsion layers on the paper at a time. So far, it has allowed me to do some very fine tuning of the different tones through out the shot.

I don't think you can do that with yellow and magenta. Right?

Da.

jeroldharter · Dec 23, 2010

mouren said:
That would be subtractive, no?

I found that tends to clump up the blacks, while with Green & Blue, I can hit just 1 of the two emulsion layers on the paper at a time. So far, it has allowed me to do some very fine tuning of the different tones through out the shot.

I don't think you can do that with yellow and magenta. Right?

Da.

Yes, that is subtractive printing in color. But, no that is not right that yellow and magenta clump up blacks.

Sounds like you might be split printing - a blue exposure for shadows and a green exposure for highlights. You can do the same with a dichroic light source by substituting magenta and yellow respectively. It works exactly the same way. Or you can combine varying mixtures of yellow and magenta to yield a specific contrast grade - just like you can do with blue and green on an Aristo VCL light source.

MattKing · Dec 23, 2010

mouren said:
That would be subtractive, no?

I found that tends to clump up the blacks, while with Green & Blue, I can hit just 1 of the two emulsion layers on the paper at a time. So far, it has allowed me to do some very fine tuning of the different tones through out the shot.

I don't think you can do that with yellow and magenta. Right?

Da.

The Yellow filter is used to subtract out Blue, and leave Yellow. Yellow light = Red + Green and the paper isn't sensitive to Red, so in essence the Yellow exposure just affects the Green layer.

The Magenta filter is used to subtract out Green, and leave Magenta. Magenta light = Red + Blue and the paper isn't sensitive to Red, so in essence the Magenta exposure just affects the Blue layer.

IIRC you get better (purer?) results doing it this way, as compared to using Green and Blue filters or light sources.

chimneyfinder · Dec 23, 2010

The Ilford Multigrade 500 and 600 heads use green and blue filtration. They crop up frequently second hand for lower and lower prices. However, I also think that (as Ilford made these) they do equate to the same result with multigrade papers whichever filter type is used.

cowanw · Dec 23, 2010

Or look for a Zone vi enlarger

Nicholas Lindan · Dec 23, 2010

Green and blue subtractive filtration is identical to yellow and magenta subtractive filtration. Making pure yellow and pure magenta exposures separately is identical, as far as the paper is concerned, to making pure green and pure blue exposures. Both emulsions in VC paper are sensitive to blue light, one is also sensitive to green light. Modern VC papers have three emulsions where the third is sensitive to blue and slightly sensitive to green.

What you are describing is green and blue additive light sources. The Ilford 500 systems work this way: two lamps with fixed filters where the exposure of the two lamps is timed separately. VC cold light systems use two tubes with different phosphors.

There were some color enlargers from the 70's that used additive RGB color.

There is no theoretical advantage to one system over the other: you can get identical prints out of either.

ic-racer · Dec 23, 2010

mouren said:
Are there any other choice? I think I would prefer not to do drop in filters, which as far as I can tell, won't give me an even spread of light.

??

mouren · Dec 25, 2010

Thank you to everybody who responded, definitely set me straight.

Mark Crabtree · Dec 26, 2010

The results are the same, but the working method is quite different. I wanted an additive Blue/Green like the Zone VI head for a long time and even tried to make something. Eventually I came up with a working method for color heads that suits me well; I've thought about trying to write that method up for some time.

I'm curious what system people use for color heads that works as well as the Blue/Green additive. I like to have the ability to adjust the highlight or shadow somewhat without new test prints (or exposure charts). I believe the additive heads accomplish that, but never did get a chance to work with one.

Nicholas Lindan · Dec 26, 2010

Using a subtractive CMY head to make the blue (er, 100% magenta) and green (100% yellow) exposures sequentially is like using an additive head. Obviously one can't make both exposures at the same time.

But it is the ratio of blue to green that is important and that ratio can be controlled by the conventional method of dialing in both yellow and magenta filtration and making one exposure.

It is possible to get identical prints either way. Some find it easier to get their heads around additive exposure and find it easier to control - split grade printing is an additive technique.

LED heads are also additive and quite easy to use for contrast control.

ic-racer · Dec 26, 2010

I'm going to guess that Mark is interested in having both colors during a single exposure, and 'riding the dials' to tweak the test prints.

You actually CAN do the same thing with a subtractive head but my personal view is that it makes the process much more complicated than it needs to be. The way it works is that the condition of both green and blue lights OFF is the same as 100% magenta and 100% yellow filtration (red, which is the same as darkness as far as the paper is concerned). To get more light to the paper you either increase your blue or green lights or you can decrease you magenta or yellow filtration. The other end of the scale would also correlate exactly being that 100% blue and 100% green bulb intensity is the same as 0 filtration on the color head.

If it is hard to conceptualize that, one can throw 100% cyan into the mix and keep it there (it won't have any effect on contrast or exposure). That way your eye can 'see' the changes in intensity. For example with 100% filtration of all 3 the baseboard will be dark, just like both green and blue bulbs being off. As you dial OUT magenta, the light will get brighter green to your eye.

Heat removal and dichroic bulb life can be an issue using the dichroic head that way, I suspect that is one reason it is not so popular.

Both 'riding the dials' and split grade printing with 2 exposures drive me crazy because the changes in mid tones are too much with any effective change in coloration.

Nicholas Lindan · Dec 26, 2010

ic-racer said:
... The way it works is that the condition of both green and blue lights OFF is the same as 100% magenta and 100% yellow filtration (red, which is the same as darkness as far as the paper is concerned).

That's a much better way of looking at it.

If you set all three dials to 100% the result should be black (well, "dark", the tint depending on your head). Then dialing down the yellow filtration will produce a visible blue and dialing down the magenta will produce a visible green.

Mark Crabtree · Dec 26, 2010

ic-racer,

That is an interesting thought, and one that never occurred to me. I agree that it is probably not entirely practical.

I've used color heads with VC paper for a couple decades or more now. The blue/green heads just always seemed like an elegant method of working with VC paper. They don't seem to appeal to many in the responses in this thread, so I was just curious what approach other people use for adjusting their contrast with the dichro heads.

John Koehrer · Dec 26, 2010

There have been some articles about DIY LED head using blue/UV and green LEDS. I believe there was just an update to one of them using a Beseler 45 enlarger.

EdSawyer · Dec 26, 2010

An obvious choice would be the Minolta/Beseler 45A color head, which is RGB additive, has a fabulous control system allowing changes of 1% or less (works in CCs), and has a great analyzer built in too. Of course it's a fantastic color printing head also, but could work for Blue Green additive B&W printing too. They go for a pittance on Ebay. I have 4 of them, one I am using and 3 spares. I don't think I paid over $100 for any of them.

sebuschi · Jan 18, 2011

Heiland electronics in Germany has a cold light solution. Unfortunately it seems the description is only in German on their website:http://www.heilandelectronic.de/html/deutsch/produkte/kaltlicht_main.htm
(There's an email button on the website.)

It's made with LEDs and can be made in the formats 6x9 cm / 4x5 inch / 13x18 cm / 8x10 inch. Also special versions are possible.

PS: I'm not related to Heiland, I'm using an Aristo VCL 4500, but since these are no more available, if I'd need a replacement (fingers crossed) I probably would go for that one.

Advise needed: Looking for an additive filtration(Blue & Green) enlarger

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Advise needed: Looking for an additive filtration(Blue & Green) enlarger

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