Lighting Stuff

[pmark23]

Oh yeah, baby!

I ordered a carton of Osram film fluorescents from Germany -- only $10 each, including shipping! These will be used to build a unit of 20 lamps to simulate diffuse sunlight through a large window.

Ballasts are dual electronic Chinese. About $3 each. The only other ones available here are German for $70 :shocked: . Since I need 20, I'll be going for whatever's cheapest and works. The Chinese ones may need a bit of modification to stabilize the HF. They're quiet and don't get hot though.

The ballasts are rewired to overdrive the lamps by 2X, resulting in 1.5 times the output. The lamps are regularly 36 watts (2850 lumens) -- 200 tungsten-equivalent watts. Overdriven each will pump-out 300 tungsten-equivalent watts per tube. 20 lamps will produce a tungsten-equivalent 6K fixture, and only consume 1kW.

Still experimenting with ballasts, but things look good so far...

 

[3xm]

keep us posted!

 

[Andrew Brinkhaus]

Looks interesting. Have you researched overpowering the OSRAM tubes? I can see that shortening their life dramatically.

 

[pmark23]

For $10 a tube, I don't care if they burn out twice as fast -- even four times as fast. If I only get 5000 hours out of them instead of 20,000 hours they're rated for, that's still several years of use on a set.

On the aquarium forums (these guys are overdriving fanatics) people have 4x overdriven lamps running continuously for a year.

 

[Cool Lights]

This kind of stuff is great for green screen lighting too. So the frequency wasn't high enough? Was it flickering at some shutter speeds in your camera? What did you do, modify the circuit to get it to go higher frequency?

 

[pmark23]

No, the frequency is fine, just that the two sides of the circuit drift out of sync, and you get trippy pulsating patterns through the tubes. It doesn't show up on video though, and they don't flicker.

The patterns go away when the tube warms up, so maybe it's nothing to worry about. Still testing...

 

[Cool Lights]

Thats a common phenomenon and so I wouldn't worry. Its particularly the case in the winter and can take a bit longer during the warm up period for it to go away. Not much can be done about it really.