Thinking about up-grading to a cold light head to replace my condeser head. However, I've heard cold lights can be very hard to print compared to condenser. Any truth to this? Any thoughts to cold light vs. condenser?

Thanks in advance...

-- Craig Uecker (bwzone@clinic.net), December 26, 2000

Answers

The thing about cold light heads is that Fred Picker used to recommend them to death and started a myth that they were miles superior to any other type of light source, in order to sell his brand.

That said........... the GREAT thing about a cold light head is that, being a *diffused light* source, it is generally a lot more forgiving of imperfections on the surface of the negative than a collimated light source (what you get from a condensor head). It saves you a lot of time having to retouch artifacts post print. They are also generally more evenly spread light sources, centre to corner.

You should note that cold light (coiled fluorescent tubes) heads are NOT the only diffused light sources in existence. The other more common, and more useful, IMHO, diffused light source is the ubiquitous dichroic colour head. What's a dichroic head? Well, you find them in all the current colour enlargers being manufactured.

The basic principle behind a dichroic head is filtered light aimed into a 'mixing' chamber (just a simple box with evenly white walls inside), that comes out one end which has a translucent perspex. The light enters at right angles to the exit hole.

A colour dichroic head is good for use with multicontrast papers since you just need to dial in the filtration needed.

All these said, a cold light head might be your ONLY option for a diffused source, if you want to modify your current enlarger that is.

Now, is a cold light head 'harder' to print with? Yes and no. First of all, you basically need to develop for a contrastier negative than what you're doing with your current setup. Think this way: the entire reproduction process is a SYSTEM. You change one thing, something else has to change to keep equilibrium. You need to test how much time to give but something like +20% t is a probable starting point. Second, it CAN be annoying if you want to use multicontrast filters to change paper grades, but there are either work arounds to this, or you can buy a costly multicontrast type cold light.

BTW, the table of dev times you get in them instruction sheets that comes with black and white films these days are all tailored for DIFFUSION LIGHT sources. And modern multicontrast papers are usually tested with dichroic diffusion light sources with 3200K halogen bulbs.

-- K H Tan (kahheng@pacific.net.sg), December 26, 2000.

I just got a dichro head and love it. Thanks to all who hounded me about the old condensor head. Stuff that took many attempts to print now print easily. James

-- lumberjack (james_mickelson@hotmail.com), December 26, 2000.

Craig: I have considerable experience with both cold light and dichroic heads. I have a cold light at home and used a dichroic enlarger at work for years before I retired. In my humble opinion, the dichoric heads are a little easier to use and give the same results as a cold light. They do not have to warm up as does a cold light and the light output is a bit more constant as the cold light changes as it heats up. Filtration is also easier. On the negative side, they are much more expensive to purchase and the bulbs are a bit expensive and don't last long. A cold light tube lasts forever and is relatively inexpensive to purchase. I use filters with mine without much problem, but you have to make your own adjustments to the filters. I do not have the head made for filters, just the standard head. Without filters, the contrast is about a grade two or three. I print most of my stuff without the filters. The difference between dichoric or cold light and condenser light sources is considerable. With the cold light or dichoric, the highlights don't block up, there is much less spotting and the prints seem to glow. I hate the thought of having to go back to condensers. I have made direct comparisons between prints from both sources and the cold light or dichoric wins hands down. I use an Aristo cold light on an ol' D-II Omega and it does everything I want an enlarger to do.

Regards,

-- Doug Paramore (dougmary@alaweb.com), December 27, 2000.

I too have a cold light at home and dichros at work. There is definitely a beautiful glow to the cold light. I do recommend, if you go with Aristo's, get the more powerful version. I toyed with the idea of trading in mine and going with the daylight version but my development is tuned to my system so I'll stick to what I have for now. You will very much enjoy cold light and you'll see an amazing difference in your prints. Do one thing before you disassemble... Make a perfect print with your condensers and then make a perfect print with you new cold light... and let us know if your a "convert"! Cheers

-- Scott Walton (scotlynn@shore.net), December 27, 2000.

I'm only going to add to what's been said above, since it all sound advice.

I found it difficult to focus and compose with my Zone VI VC head.

1) Most cold light sources have no yellow light, the human eye is most sensitive to yellow, and least sensitive to blue. So your image is compose of colors to which your eye is least sensitive. Diffused dichroic heads don't suffer from this. They produce a fairly "white" light. The result is more light to see, but less actinic light (the light the paper is sensitive to.)

2) With cold light heads, anytime you are printing smaller than the full area of the head, you are wasting light. For example, a 4x5 head is about 6" in diameter. For 4x5 you are using 71% of the light, for 2-1/4 x 2-1/4, you are using 20%, for 35mm you are using 5%. This wastes a lot of your light. No problem for printing, if you can stand the long exposure, but the image can get very dim (at least it did for me) and composing & focusing was a pain. With consensors you can get different condensors to maximize the usage of the available light (Beseler's "cone of light" produces a similar result) and with diffuse dichroic heads you can get different mixing boxes to use more light.

Finally, if you do opt for a cold light head, though, make sure it has blue and green phosphors for printing VC as well as graded papers, unless you intend only to print graded, in which case blue is OK.

The variability of light

-- Charlie Strack (charlie_strack@sti.com), December 27, 2000.

I forgot to delete "the variability of light". Ignore it.

-- Charlie Strack (charlie_strack@sti.com), December 27, 2000.

The difficulty about which you've probably heard is the variability that you can experience as the head warms up and cools down. (As it's used.) To combat this problem, later models included a heater to help maintain a constant temperature. Installing a sensor and using either the Zone VI or the Metrolux compensating timer will eliminate this variation. (Or, purchase a diffused head with the sensor already installed.)

Frankly, I prefer the condensor head for printing 2 1/4 or 35mm negatives. It's a matter of personal taste; neither is correct or incorrect.

If you decide to proceed with the diffused head and don't want to shell out the $400 that a compensating timer can cost, call the technician at Arista. He's knowledgeable, and he will suggest a regimen that you can use to help control the variation.

-- neil poulsen (neil.fg@att.net), December 28, 2000.