View Full Version : Procedure for using a high intensity UV lightbox

1-Aug-2016, 16:25
Up to now I have heard that it was best to turn on your high intensity fluorescent light box on at the beginning of the printing session and off when you're through using it for the day for two reasons: 1. Fluorescent tubes take a while to warm up to full intensity. 2. The bulbs will last longer.

After watching some Platinum printers on YouTube, I see most them using their high intensity fluorescent light boxes on timers just like you would do when using an enlarger. Asked an electrician if turning fluorescent tubes on and off a lot would shorten the life of the tubes and was told yes but only after turning them on and off many thousands of times. Also the warm up time is insignificant in a room with the air temperature of 70 degrees. A relative is a retired electrical engineer, and he told me not to worry about using a timer with today's fluorescent starters and tubes.

Can anyone out there shed some light on which procedure is the best to follow?


Michael Mutmansky
1-Aug-2016, 17:26
He's right on the ON-OFF-ON (lamp cycling) answer. Your lamps will last longer if you only turn them on for the exposures compared to running them all day long. The exception to this is if you are cycling the lamps A LOT, which probably isn't going to happen with a normal exposure unit. If you were at a college and the exposure unit was cycling all day long, I'd think about running them continuously.

He's wrong on the warmup.

I did some tests on this when I used a FL BLB bank, but that was 15 years ago, so I don't have the results and longer. Regardless, the warmup is considerable and does mess with the exposure in ways that are predictable (once you understand them). Whether there is an issue for you partially depends on how consistent you are with your exposures and what level of consistency you demand from your prints.

For example, if you ALWAYS make a (for example) 5:00 length exposure from a cold lamp, then you can probably predict that the exposure will be relatively consistent from one to the next, given the same exposure time.

But... as soon as you want to adjust the exposure, you will have a bit of trouble, because when you go to a 10:00 exposure, you will not double the exposure (1 stop), because the second half (after the first 5:00) will be with a warm lamp. So, you will not be able to do the simple double/half per stop exposure adjustments without doing some testing to try to compensate for the warmup.

Some people will preheat the lamp (run it for 5:00 or so), and then slide the print in for exposure. That helps eliminate the warmup, but it takes more time and attention.

If you are pushing a lot of prints out, you simply can't afford the time and attention that the exposure unit will require to make consistent results, so many people use in integrator. Even if you can afford the time, I believe an integrator will produce more consistent results regardless.

So, it comes down to how critical you are, what your goals are for printing, and other similar variable that can't be defined by anyone else but you.

If you are just starting out, I would say to buy a print frame and use the sun for a little while. Then, watch for a used Nuarc or Amergraph exposure unit in your area when you get more serious. At this point, I wouldn't use FL exposure units anymore, I'd probably build an LED exposure unit if I wanted a diffuse UV source (which I do not, I prefer columnated light sources). They DO NOT have the warmup issue, and you can make them any size you want rather than be limited to the UV FL lamp sizes. They aren't susceptible to over- or under-temperatures like FL either, and they use less energy.

Source: I'm a PE related to lighting and also a pt/pd printer and photographer.