Newbie lighting question from artist

[Kath]

Hello all. Please forgive me if I'm posting in not the best place....I am looking for some expert advice and have scoured the web and found you all finally (and I've done a search here and still can't find this answer).

I am an artist using two 85w 5200K 90 CRI compact flourescent bulbs in my studio set-up as my general lighting so that I can see the greatest range of color in my painting (the room is painted dark so there is no glare -- not white walls looking like the afterlife with all that light). I am having these bulbs hardwired into my ceiling, and could not find a ready-made fixture that could handle the 85w times two, and found a lighting store to rig up a fixture. I don't care that it's not pretty.

Others I study with are placing those same bulbs in their studios into their overhead ceiling fans where the sockets are rated to 60w each. We cannot find information on the heat output of these types of bulbs to see if this is safe. The assumption by others is that the heat output is so much less than incandescent that it's OK, but some are thinking that the 85w still is reflecting the heat generating of an 85w incandescent, not much less.

Is this OK?

(So much info here -- thanks! This will help immensely in learning about lighting for special lighting effect set-up for subject matter.)

 

[BVH]

:welcome:

You seem to be going after a light that is as close to daylight as possible. I'm wondering why you wouldn't go with a more "full spectrum", (98 as opposed to 90 CRI) closer to daylight color (6500K as opposed to 5200K) bulb? To me, it would be much easier to buy a typical $15.00, 2-tube, T8 fluorescent fixture at any Home Depot, Loews or similar store and then buy two of the 6500K, 98 CRI tubes from the site linked below. Then you'd never need to worry about the heat issue and you'd probably get a little more light. A bonus is that most store-bought fixtures are UL Listed. I bought three of these for my office and love them.

http://www.budgetlighting.com/store/agora.cgi?page=lumichrome_full_spectrum_lamps.html

 

[Kath]

Thanks so much for the reply!

I should go for a higher CRI, you are right, and just had trouble finding them. The reason I didn't go with tubes this time is that the size of my room would have those spread out over a larger area to get the same wattage total -- I see those only come in 40w each or so, so more tubes required. This doesn't allow the artwork to be far enough away from the light source to allow for no glare / shine / reflection on the wet areas. Right now in my 12' x 12' space I can have the art far enough away from the bulbs that I am not looking at "shine" or glare from the wet areas. Others have smaller rooms that they are lighting.

And the reason I chose in the 5000K range instead of higher is to reproduce daylight at noon. I will experiment with higher ranges, and will probably swap out bulbs after mixing colors to see if I still see the entire "gray scale" or "brown scale" etc I've just made, and how it looks different. But I'll start with this range for now.

So that is why we are questioning the "shortcut" of sticking an 85w cp in a 60w socket.

 

[VanIsleDSM]

I suppose it would depend on whether the fixture's limiting factor for the 60W rating is power or heat. Most likely heat I would imagine.

An incandescent produces alot of heat, true. However only about 4% of this heat is conducted heat, the other 96% is IR radiation that will not contribute to the heating of the bulb or fixture, not directly anyway. Some of that IR will be absorbed by the bulb itself, and the socket area, and then conducted into the fixture, but much of it is just projected into the room.

An 85W fluoro will make less heat per unit of power going in, but almost all of this heat stays in the lamp, very little is expended as IR radiation.

So the answer? I'd say there are too many variables to figure it out mathematically.. and the best bet I would say would be to put the 60W into the fixture and take some temp measurements, then the same with the 85W fluoro bulb.

My guess? the 85W fluoro will run slightly cooler than the 60W incan around the bulb base.

 

[Kath]

That is a great answer. Thanks so much. Actual temp reading is a great idea.

I'll see if I can do that myself in the next few days and post the answer back.

 

[red_robby]

what is the wattage rating printed on the bulb? is it labeled 85W?
if it is, you should not use it in a 60W rated fixture for an extended period
of time, change the fixture or socket if you want to keep that using that bulb.