How are "cold lights" builtgreenspun.com : LUSENET : Large format photography : One Thread
I would like to build my own 8 x 10 enlarger. I would like to use the so called cold light. I notice that these cold lights are extremely expensive in larger sizes. What makes them so darn expensive. Is it possible to purchase the components and make ones own cold light.
-- kevin J. Kolosky (firstname.lastname@example.org), June 10, 1999
I don't see why not. Just get yourself a bunch a 12-inch fluorescent tubes, some opal glass, and make a box to hold everything together. Watch out for the heat generated, even though they are 'cold'.
I can't say why they are expensive, but I suppose they are hand- built, with proper calibrated and stabilised electronics, etc.
-- Alan Gibson (Alan.Gibson@technologist.com), June 11, 1999.
Ansel Adams built his own 8x10 enlarger from an old 11x14 view camera. My factory Omega cold light head literally consists of a round flourescent tube and a 4x5 square of white Lexan in a can.
-- Brian C. Miller (email@example.com), June 11, 1999.
I have read the two answers to my question. First, I do not think that the tubes are plain old flouresent tubes. If anyone knows where to get the correct tubes please let me know. And secondly, does anyone know what is required to "stabilize" these tubes. Why I ask is because it just doesn't seem logical to me that a light source consisting of a few tubes inside a couple of dollars worth of sheet metal should cost over $1000.00. Thank you. kevin
-- kevin kolosky (firstname.lastname@example.org), June 11, 1999.
hi actually, i would say that's pretty much the case for everything we buy. i mean, what's in a camera - a pair of plates and a bellows and a piece of circular aluminium for a monorail. what we pay the larger amount for is that somebody took the trouble of making the initial mistakes and ironing them out and the fact that we are uninclined to take the trouble/lack the knowledge etc. you also, of course, pay for precision engineering, a 'guarantee' that stuff is aligned etc. if you like tinkering, there is no reason you can't make it. you could call aristo re the light. re the stabilization, the usual stabilizers will cause some problems. i've had noticeably flickering lights when i used a stabilizer meant for condenser sources - the flickering disappeared when i removed the stabilizer. i'm afraid i didn't understand the explanation - something about voltage and cycles per second. i believe there are stabilizers meant for cold lights. and ansel adams ('the print') mentions a (horrowitz?) stabilizer which actually monitors the light output and keeps that constant. hoep this helps. dj
-- N Dhananjay (email@example.com), June 11, 1999.
forgot to add. another reason 8X10 enlargers cost more than 4X5 is that there is a much more limited market for them and so the economies of scale are just not there.
-- N Dhananjay (firstname.lastname@example.org), June 11, 1999.
Kevin, I'm interested also in homemaking a cold light box for an old 5x7 enlarger; I have found a lot of different fluorescent tubes, in different sizes, all of the same name brand, Philips, G. Electric or Osram. I have seen one really cold (cold color, blue) only available in big tubes, another cold also but less than the first one (blue- green) and the third have more yellow, is a bit hot (green-yellow). The rest of the tubes are hotter, from yellow to red; I understand that the photographic papers are sensibles specially to blue light, the coldest the color of the light, the shortest the time of exposure. In addition, I think we need a instant starting device for the tubes, and a stabilizer could help also. It's difficult or impossible to find in my city (Madrid, Spain)light sources like the Aristo or Zone VI, I'm obliged to build my own difusion head. I'm not an expert, the opinion of a tecnician will be great. If you want to share some ideas, don't doubt to send me an e-mail.
-- jose angel (email@example.com), June 11, 1999.
The actual cold light and associated circuitry are really not that expensive(I purchased an 8x10 from Aristo about five years ago for $250) however the necessary adaptation to a specific enlarger would drive it up some... the higher cost for variable contrast applications is the result of the necessary "balancing" circuitry needed to control the tube output(s). These are not the simple flourescent tubes found in conventional applications and there are a number of different "compounds" available for different light temperature outputs. (I have the W5500 which ostensibly provides a roughly "daylight equivalent" and if I had it to do all over again I would probably opt for the W3100 simply to more nearly approximate the color temperature of a tungsten-source diffused lamp). In essence you have the housing, the tube (or for VC, tubes), transformer, a thermal switch which helps maintain output stability by regulation of the lamphouse temperature and a diffusor (similar to opal-glass). Admittedly, VC by means of a "dial-in" would be convenient but for the difference in price between a single and multiple-tube sources, I'll stick with the single. Unless you are in a situation where voltage fluctuates fairly severely, the variable output device sold by Aristo (ca. $80 if memory serves me correctly) which is a simple "autotransformer" or VARIAC should be sufficient to achieve an order of reliability greater than most of us require. One of the features of this, compared to flourescent tubes, is that you really do need "instant-on" capability because of your timer circuit - something not easily (if at all) attainable with flourescent tubes. This "inductive load" (the transformer) is the reason that some timers cannot handle the transient caused by initializing the circuit - these are generally the solid-state type timers and even they can be adapted by means of a relay. Hope this helps. JE
-- Joel Edmondson (firstname.lastname@example.org), June 11, 1999.
You can find answers to most of your questions at the manufacturer's own web site:
-- tony Brent (email@example.com), June 11, 1999.
Joel, that's the response I need. Thanks a lot. Only one more question; Why could be desirable a lower temperature lihgt source? Could it be better for enlarging in VC papers?
-- jose angel (firstname.lastname@example.org), June 12, 1999.
I went to Aristo's web site and all I found there was a catolog for their light sources. Does anybody out there know whether I can walk into a store (hardware, lighting, etc.) and buy one of these cold light tubes so that I can put it in a housing. I know of the Horowitz stabilizer as it was developed in conjunction with Zone VI and I suppose could possibly be purchased from Calumet, although I thought I read somewhere that Calumet might not be carrying Zone VI stuff anymore. Anyway, what I am looking for is more specifics. part numbers, etc. Thank you everyone for your contributions. Kevin
-- Kevin Kolosky (email@example.com), June 12, 1999.
Kevin: Have you thought of using a Mercury Argon grid like Ansel Adam's. I too am planning to build a 4x5 enlarger with cold-light (and using my 4x5 field camera in front of the light box). Mercury argon grid with a diffusing glass in front should work fine (you may need to add a focussing photo-flood lamp behind the grid for better focussing since the grid is pretty low in intensity).
If you have any more data on the Mercury Argon grid please let me know.
-- dileep prakash (firstname.lastname@example.org), January 18, 2000.
There are two issues that I'd like to address. 1. The design of the grid and container in which they are housed is a bit more critical than initially thought. I had a great deal of trouble with an old cold light housed in a can. Apparently the eveness of illumination was ever so slightly skewed. This created problems for me at the extreme edges of my prints. I didn't realize this until I bought a new head that had a perfectly even design. Even a piece of opal glass (mine was actually plastic) isn't enough diffusion at close proximity to the tube. 2. I had to compensate the output of this original design with a light yellow filter to allow me the use of a full range of filters with VC paper. When I got my new head (Aristo VCL-4500), a dual grid type, I not only was able to ditch the filters which made exposure estimation a lot easier, but I discovered I now had at my disposal, a far wider range of useable contrast grades. The phosphors in the tubes, I'm told make the difference. Maybe the construction of the actual enlarger is less critical when it comes to materials and configuration, but I would be mindful of having an even light source of the right color temp. and pay close attention to the alignment of neg. carrier, lensboard and easel.
-- Robert A. Zeichner (email@example.com), January 18, 2000.
They are so expensive because they are only built by hand in the Northernmost reaches of Alaska during wintertime to assure the cold properties of the lamps.
-- Dan Smith (firstname.lastname@example.org), January 19, 2000.
A cold light is a specialized flourescent light. It differs from the ones you buy at the hardware store in these areas.
1. Geometry: The diamater of the tube is small, about 1/2 inch. They get a lot of convolusions (bends) in a small area to give even illumination.
2. The phosphors they use are selected for the appropriate color of light: blue for graded papers, green & blue for variable contrast. These provide high intensity for photographic paper. The standard flourescent tube provides a wider spectrum to match what we need for visual uses.
3. They are thermostatically controlled. A simple fluorescent tube varies a huge amount based on a lot of things. Temperature, how long it was off before it was turned on, how long it's been on, etc. Temperature seems to be the characteristic that best controls these variations, so the cold light heads have a thermostat and a warmer to mimimize the variations. For perfect control, however, you have to monitor the light output and compensate for the variations. Zone VI used to build a stabilizer to do this. You added a photocell to the head and the stabilizer "watched" the light and adjusted the voltage to make the intensity even. Later, they and others made timers that adjusted the time according to the light intensity.
4. Standard fluorescents glow long after you've shut them off. I suspect the cold head manufacturers do something so the cold heads don't do this. I just don't know what. Probably has to do with the phosphors.
Can you make your own? Sure. But it probably won't work well because of all these issues, and it would cost you a lot to address each of the problems. If you want to make your own, try incandescent lights, which is what Ansel Adams did. Then you only have to worry about heat, and the current, and ventilation because of the heat. What am I saying? Just buy a cold light head from Aristo or Calumet (Zone VI).
-- Charlie Strack (email@example.com), March 21, 2000.