Aristo B64 cold light

Hi,

In my ongoing enlarger conversion project, I’ve acquired an old Aristo cold light head (old enough to have only one power cord) with a bulb labelled “Aristo Grid Lite B64”. The light looks very blue, and I expect I’ll need a yellow filter to use it with VC paper.

I couldn’t find any information about this bulb, though. I’ve written to Light Sources asking if they have anything; is anyone familiar with the B64 bulb type?

Thanks
-NT

I've used Aristo heads since early 80's and don't remember that name/number. Is it the bulb itself or the fixture?

George Collier said:

I've used Aristo heads since early 80's and don't remember that name/number. Is it the bulb itself or the fixture?

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It’s the bulb. I’ve been unable to find information on this bulb type, except for one post on LFPF where someone said they had old Aristo literature that mentioned it as a replacement bulb type.

The fixture has no identifying information at all, but it’s a ringer for the one in a 1949 Aristo ad that ran in Popular Photography. I think it’s ancient and possibly intended to fit on a Beseler 5x7.

-NT

Seems no one knows about this bulb. I found a phone app that measures colour temperature and tint; I don’t know how accurate it is, but it showed sane-seeming results in sunlight and for my incandescent enlarger bulb, so I’m guessing it’s basically functional.

The B64 bulb, unfiltered, is too blue to measure: The app says >16000 K and at least +0.03 tint. When I added CC30Y+CC15Y filters, it came down to about 11000 K and just below +0.03 tint. So it looks like filtering this lamp for VC papers will be a significant challenge. I may have to use it only with graded papers, and work towards a controllable LED light source as a more general solution.

-NT

Even the (presumably later) Aristo/ZoneVI tubes for the single tube heads were rather blue. I have read contradicting reports of filtering them for VC use. At least one person wrote that a yellow filter in permanent place allowed standard VC filters to be used, others have said that so much filtering is needed that it isn't successfull.

Your color-temperature meter won't give an accurate reading on a discontinuous light source like a fluorescent tube, especially one that is optimized for blue and green wavelengths only. Color temperature in K is predicated on a black-body spectrum that (usually) contains all wavelengths, just in different proportions. The missing red in the Aristo tube will skew the results to a higher K number.

I would take a look at the light source through a #58 green filter and a #47 blue filter and see what it looked like. These are the color-separation filters for in-camera separation for making color prints from B&W negatives and are rather sharp-cut.

The luminance visible through the #58 filter would be the green component and the low-contrast light for VC paper. Compare this visually and with a light meter to the light transmitted by the #47 filter. All you really need is enough green light to expose through the #00 filter. Even if the blue and green components are not equal, as long as you have enough green to do the job, you'll be able to get a full range of contrasts from VC paper. The only thing is that the increments between filters will not be equally-spaced if the two color components are not balanced. That just means longer exposure times for low-contrast settings and the use of filters closer to the low-contrast extreme if the green component is significantly less than the blue. E.g., to get "normal" contrast, you may have to use a #1.5 or #1 filter instead of #2. If you have a color head, just dial in what you need.

If the light from the cold-light head appears cyan (blue-green) and not just blue, I would wager that it would work just fine with VC papers.

Best,

Doremus

Thanks for the comprehensive reply. I don’t have a blue filter, unfortunately, but I guess I see where the blue/green balance is the important thing and I don’t necessarily need to match the colour of the incandescent bulb. The tint axis is very far towards green, so maybe there’s hope in that respect.

-NT

Yeah, if you have enough green and blue to get both highest and lowest contrast, then you're in business. It just won't be as evenly spaced as an incandescent.

D

john_s said:

Even the (presumably later) Aristo/ZoneVI tubes for the single tube heads were rather blue. I have read contradicting reports of filtering them for VC use. At least one person wrote that a yellow filter in permanent place allowed standard VC filters to be used, others have said that so much filtering is needed that it isn't successfull.

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I did this a while back and it was successful, though I did not feel the contrast changes from 1 though 5 were linear (just by eyeballing). You can find details on the web; I'm not sure I can find my notes. But, as I recall, I used a Roscoe gel that was close to the proper filter but not exact.

A CP40Y or CC40Y is the filter said to correct the "blue" Aristo/Zone VI light source to use modern VC papers. I've been printing with one of those heads for over 30 years. Long ago I tried the yellow filter... didn't make all that much difference. I gave it up and just use under-the-lens VC filters now. This means that I'm often using lower contrast filters than some people would call 'normal'... but there have been very few if any negatives that I could not print. It's true that grade spacing is sometimes non-linear, but I deal with those issues as I go.
It would make sense to have a proper color head or VC head, but so far there have always been more important things to spend money on, and I get good results easily from this non-optimum setup. So it goes.