resummerfield, there was a review of the LED head in View Camera. Alan Ross evaluated it. As I recall, he thought it was okay (but he is still printing with a V54). LED source has problems acheiving high contrast levels as the blue LEDs are not blue enough to generate the higher grades. Also not as bright as the V54.
White LEDs would suffer the same problem as they are blue LEDs with a phosphor to generate wavelengths longer than the blue emitted. Doesn't go the other way, i.e. you can't use a phosphor to go to shorter wavelengths.
There are violet LEDs and UV LEDs, but I have not seen these used in light sources. They are much harder for the human eye to see and not as bright as the blues.
i've actually owned aristo VC4500, VCL4500, D2 and D2H heads along with a metrolux timer...and I use a beseler 45S dichro head and a D2H where I work. My main enlarger at home was first the VC4500 (pre-V54 tube) that I later on had a green tube installed in, to make the variable contrast unit. When I got the metrolux, I mounted the probe to the blue tube, aimed at the green at an oblique angle. I calibrated the first channel (lux 1) for a blend of the two tubes at a setting of 3.5. It works good enough--tends to run at slightly faster pace for the higher settings, and slower on the lower end of the scale, but the output is consistent. It's just like getting used to the settings on the head--the speed of the timer runs faster & slower, just like the numbers represent the blend of the tubes--not a specific grade of paper. Once you get used to it, it's no big deal. I calibrated the second channel (lux 2) for the full blue, or the adjustable blue tube. With this, I can flick the settings over in a snap, and then do burns etc, or use the two channels for green/blue spit printing as well. I've gotten pretty used to it over the years, but it might seem kinda quirky to some.
I bought another VC4500 a few years ago, because it was dirt cheap used, and I thought I could get that upgraded to a VCL--but since it has that new tube (v54) in it, aristo doesn't do that anymore. So, I was stuck with it--I tried using it on my second enlarger, but I liked the VCL so much more...I took it into work, but I liked the dichro head more, so it just basically became a doorstop more or less.... I finally got rid of it last month. There's nothing really wrong with it--it worked good enough, it's convenient with the filters above the lens--but honestly, I find it easier to split print with the filters below the lens on the older aristo heads...if anyone is interested in it, it's up for sale at a camera store, where I traded it.
I didn't think of glass filters. I would still obsess about dust but that is alot cheaper that a VC head and potentially compatable with some of the DIY LED heads with white bulbs.
Originally Posted by resummerfield
the glass filters wont show the dust Jerold. They are not in focus. I use gels in front of the light source of my 138 Durst. Before I got the Aristo head I had an Elwood 5x7 and used just plain gel filters under the lens without any problems what so ever.
Do you have a pointer to such turret filter holders?
Originally Posted by jeroldharter
Sponsored Ad. (Subscribers to APUG have the option to remove this ad.)
My filter turret holds 3 filters and I had it machined for my enlarger. The Durst Latirad filter holder (like this one on Ebay) was the basis for the design. The Latirad holds 70mm filters, and the Tiffen 72mm filters will fit, once you remove the Tiffen metal ring.
Originally Posted by jstraw
It produces whatever light output the controller demands of it. If it be the max then it is the max...
Originally Posted by Loose Gravel
One tube is always at maximum intensity and the other tube is turned down to adjust the contrast. It is the same with every other head. If it is a fixed illumination (undimmable) head then the timing of one of the tubes is reduced in relation to the other. The effect in printing speed is the same.
The ZBE gives the option(s) for various control strategies where contrast can be changed but printing time is kept the same - in this case the lower contrast settings do cut down the light. The same happens with regular VC gel filters without much complaint. The ZBE also has the option of keeping the printing times at their shortest and automatically adjusting the printing time as contrast is varied. And programming this function for the responsivity of various papers. And programming the blue/green balance for various grades for various papers so the same dial setting produces the same contrast on all papers. And scanning the image on the easel and for the selected paper and automatically selecting the best grade and exposure for the image. And, and, and. To compare this with an Aristo ...
Compensating timers/light integrators work mostly, and mostly they work well enough. But so will a plain Aristo if you keep careful watch over heating time and printing duty cycle. Problems with VC cold light heads arise as the lamps age. The differential in light output changes and unless the integrator has a sensor for each lamp the integrator will lead one down the garden path. And individual lamp sensors won't detect the change in the lamps spectra as the lamp ages, for that one needs filters matched to the sensitivity curve of the emulsions or an integrating spectrophotometer.
Whether the features and precision of the ZBE is of use is something everyone has to judge for themselves - as the story goes Edward Weston produced prints with a peice of glass and some sunlight for printing and a raincoat thrown over a card table for a darkroom. The equipment is not the limiting factor.
It seems the owner will be happier with something simpler. But sell the head on to someone who will appreciate it and be willing to keep it running.
Nicholas ~ Just prior to your post, I was able to find the ZBE website, as well as their .pdf manuals for my light source. Reading through the materials, I was amazed at the capabilities of the ZBE. I received it w/out a manual b/c the original owner had died. I've been using it's basic features only b/c I was unaware of the various other features.
I didn't mean to imply that I wanted to dump this light source, nor that I was unappreciative of it. I would love to keep it running but, alas I am not the type who can tear something apart, tweak things, and return it to working order. If I tear something apart, I break it. Period.
I am considering a call to a Canadian company who services the ZBE to see about replacing the light tubes. I read that they are rated for 10K hours of use. I'm certain that the original owner could've easily put that many hours on them. And since the light flickers on occasion, that might be an indicator that they need to be switched.... if anyone makes them anymore.
It seems I may have irritated you w/ my posts. Just wanted you to know that was not my intention.
[QUOTE=SusanK;402887]I am considering a call to a Canadian company who services the ZBE to see about replacing the light tubes. I read that they are rated for 10K hours of use. I'm certain that the original owner could've easily put that many hours on them. And since the light flickers on occasion, that might be an indicator that they need to be switched.... if anyone makes them anymore.[QUOTE]
After thinking about my experience with intermitent cold-light sources - flourescent lamps - the major reason they flicker is that they are loose in their socket and they just need a little wiggle now and then. If the lamps have wire leads then the screw that clamps the lead may be loose. See if you can find an electronic engineer/tech/hobbiest who can open it up and see the connections are tight.
10,000 hours is a _lot_ of hours. There are about 2,000 working hours in a year. Pulling a number out of the air ... I doubt an enlarger has the light on for more than 10% of the time day-in-day-out. That gives 200 power-on-hours/year and it would take 50 years to accumulate 10,000 hours on the lamp.
But the 10,000 figure is most likely based on the factory noticing that if left on more than half the lamps are still burning a year later. A fair middling number probably go belly up after only a few hundred hours.
To see if it's a failing lamp can you see if there is there any blackening at the ends of the lamp?