I was looking at the packaging my Ushio T15 came in today when I noticed there was text inside. It answers all questions we have had about whether or not the UV filter is neccessary, as well as a few interesting (I think) facts:

The first sentences:
"Metal Halide discharge lamps emit ultraviolet radiation which is harmful to eyes and skin! Metal Halide discharge lamps should only be used in enclosed fixtures with ultraviolet absorbing filter glass. Failure to do so may cause serious skin and eye inflamation. Do not use these lamps where any un-filtered light is emitted from the fixture. Do not operate these lamps if the ultraviolet absorbing filter glass is broken or not installed."

It also warns about operating lamps with cracks or even scratches in the outer envelope, which surprised me. Apparently these minute stresses can cause the lamp to explode.

If I were you, I would heed the warning of the USHIO company and USE A UV FILTER. Who knows the effect it can have on your eyes after watching the projector for long periods of time. I understand that you are exposed to moderate levels of UV radiation when outside, but we don't really have any tangible data of how this compares with our lamps (that I know of) so If I were you, I would play it on the safe side and use a UV filter.

I hope I don't start a flame war. But I would hate to see anyone get hurt.

Nick

Hi Nick, Your concern is appreciated. This has been discussed many times on these boards. Ushio makes many types of metal halide lamps, and they all contain that warning, even if the lamps have UV filters built in and are rated for open enclosures. It is extremely improbably that any harmful UV would make it out of the projection lens, especially after passing through so many layers of glass on the way out. Also, in all of this time building these, we have never seen an explosion in all of the builds at Lumenlab. It doesn't mean there isn't risk, but it does mean that it is very very unlikely that terrible things will happen. As with anything in life, common sense and safety come first, and I certainly wouldn't tell anyone to look at a burning lamp. But these lamps are pretty durable and have a good record of safety.

So what you are saying is the warning is mainly there so people don't sue ushio?

I understand that the topic has been brought up many times, I hope I didn't come off as annoying. As you have said, common sense is most important.

I figured that this was a standard warning they issue, but I would have never suspected that it was also on the bulbs for open enclosures. This indicates to me that the UV is actually much less severe than they make it sound. But that label makes it seem quite hazardous =D

Your point about the lenses and glass is a good one... assuming that the transmission rates for UV and visible spectrum are the same.

Now that I think about it, your eyes probably get a heck of a lot more UV when you walk outside on a sunny day.

Thanks for the clarification,
Nick

I'ld say that if you are uncomfortable you should use the UV filter. It doesn't hurt.

I don't, but then again, I'm not uncomfortable. From my perspective the light passes through 10 layers of glass with two polarizers and a color filter that probably filters most of the UV. I do agree that there may be some danger for the lcd filters, though. I just don't know what degree.

I actually don't notice any light loss whatsoever with my UV filter. It is placed right after the tempered glass, before the fresnels. I do see a slight rainbow effect, but it isn't that bad.

The only reason I am concerned is because in my previous projector, with no UV filter and a random venture bulb, my eyes burned after extended use of the projector. When I closed them it was the worst, by no stretch of the imagination an intense pain, but it was there. Strangely, I also saw a flickering effect like a strobe light when my eyes were shut.

With the new projector I have no such problems, even though it's way brighter. I attribute this to the UV filter, but it could also be coincidence.

I hope this clarifies my reasons for this posting.

Nick

When my time allows I hope to quantify some of the UV blocking characteristics of the various components within our projectors. I'll post my results here when I get 'em: http://www.lumenlab.com/forums/index.php?s...ndpost&p=126930

Your concerns certainly aren't without justification but one shouldn't get a detrimental amount of UV coming out of the triplet.

The problem would be if someone sits staring at their exciting new bulb REAL close for a long time while it's totally unshielded.

Common sense goes a long way.

One other UV concern I would like to mention is wiring exposed to unfiltered light from the light engine. Most wiring uses plastic insulation that is not UV stabilized, and the insulation will become brittle and break off easily if exposed to UV for long enough. This is why the leads on the mogul are insulated with a more rubbery insulation covered by a woven outer liner. In a past life, I used to install UV light kits in air conditioners (to kill mold) and the manufacturers recommended wrapping exposed wiring with aluminum foil to prevent insulation degradation. I have seen the damage UV can do to nonstabilized insulation.
My concern is that someone gets damaged wiring insulation, and ends up with a fire. Be careful not to leave wiring exposed to the light engine.

It will be good to see some quantified results. I know my school has a UV meter, perhaps they can let me borrow it.

About the wiring and insulation, that is nothing I would have ever anticipated. Thanks for the warning. I will shield my wiring before the next time I run my projector. I would hate to have a short, that ballast puts out a ton of voltage!

Nick

BTW, I don't really consider wrapping exposed wiring with aluminum foil to be a viable solution since it might cause a short or even worse - exposed high voltage. The first time I read the manufacturer's fix in the air conditioner UV light kit I thought it was a pretty risky idea. Best to just reroute the wires to a safer location if possible, or engineer a hard cover out of flashing. Usually in my projectors I route a groove in one of the side panels and cover it with flashing.

I had the same thoughts about the foil. I am going to use some other substance.

I don't think the recommendation was for exposed wires. Copper is not degradable by UV, so it doesn't need protection. The aluminum is for the wire insulation. I wrapped my wires in the PJ with aluminum foil to protect the insulation from the UV. Obviousely, you want to make sure that the aluminum foil does not get close enough to the exposed ends to touch the wire or you risk electrocution or shorting.