Safe temperature for operating lights...?

[Patrick Kaplin]

Ok, I don't have much experience with placing light outdoors during colder seasons. Having recently moving to Canada, I can say I have a whole new appreciation for winter chill!

 

So, what are the dangers of operating lights outdoors during cold temperatures. Say about -10 degrees C. Should I be concerned about bulbs blowing out because of the extreme temp.? Is there any site to get information on this?

 

Thanks in advance!

[Chris Keth]

I've heard that in really, really cold temps you should leave lenses on HMIs and close the barndoors on all fixtures so it insulates the globe and slows cooling to prevent the globe popping from temperature diffences in the glass. I don't know how true or necessary this is.

 

I've had tungsten fixtures and kinos out in weather down to -5F or -10F without any special precautions and they were fine.

[Ralph Keyser]

The concern seems to be less with bulbs/globes and more with the lenses. Some gaffers that I've worked with have dropped a stack of scrims into lensed instruments and closed the barn doors long enough to heat everything up prior to turning them off. The idea is to have something warm on both sides of the lens to reduce the differential cooling and avoid cracking the lens. This is probably more of a problem with large lensed instruments (5K and up?) Other folks just turn 'em off :)

[Michael Collier]

I have shot down to -25, and other than putting some scrims in the light as they cool it doesn't seem to be any problem. I would note that you should wear gloves of some kind, on one shoot a friend of mine got frostbite instantly when he went to pick up a mombo combo stand that had been out all night. Even thin gloves will help prevent instant frost bite. Try a thin glove/heavy glove combo and you'll be fine.

 

now that I think back, I would say its really not a concern once it gets really cold. Those lights and lenses never heat up in tempature that cold, so temp differential isn't really a concern. Big guns are another story though, not sure about those

Edited November 26, 2008 by Michael Collier

[Marc Galerne]

I've heard that in really, really cold temps you should leave lenses on HMIs and close the barndoors on all fixtures so it insulates the globe and slows cooling to prevent the globe popping from temperature diffences in the glass. I don't know how true or necessary this is.

 

The bigger wattage the lamp the more lens breaking problems. What causes breakage on lenses is the thermal shock. It's is the temperature difference between the hottest area on the piece of glass and the coolest. Basically, it's temperature on the center of the lens (hottest) and the edges of the lens. When using a Fresnel fixture 4K and up (to be on the safe side) always start your fixture in spot mode as it is the position where the bulb is the farthest from the lens. You let it heat up for 5 minutes and THEN start going to flood. Same thing when you turn off: go back to spot and close the barndoors and put scrims.

The rule is AVOID THERMAL SHOCK.

[Patrick Kaplin]

Thanks everybody, my concerns are laid to rest :-) Good to know for the big lights too. I never would have known that that's the proper system to use for 4ks and up. Is it good practice to use scrims in the 4ks and up as they cool to help reduce the thermal shock problem as well?

[Michael K Bergstrom]

For 4k's and such, know what lens you'll be using and have the lens in place while the head heats up, other wise you'll crack the lense if you pop it in a hot light. And a 4k lens is not cheap at all. Another issue not addressed yet is the fact that the header cable can also get very cold, and if laid on snow or ice, you need to check the cable for breaks or wear just like if you were dealing with rain or water. When you go for wrap, be very careful with the header cables, because when you wrap the cable you can snap the cables inside if it's cold enough.

[J. Lamar King IMPOSTOR]

I recommend dropping scrims into any HMI or big Tungsten unit before turning it off in the cold. Just be sure on the PAR's that the scrim doesn't rest on the lens, that almost guarantees a crack. If possible put the lights away in a warm truck or building. Even the scrims won't help if the light stays out and allowed to keep cooling. I've seen 18K's that were cooled off to the touch, left in a stakebed and the lens cracked sometime over night.

[DJ Kast]

Good to know! I start shooting in the woods of wisconsin this weekend and it'll be chilly.