Homebrew paint booth questions

68 Coronet are the frosted a lot brighter and do they put out more light them the old fluorescents ?

Since this thread sorta drifted into LED replacements for fluorescent tubes, I thought it would be worthwhile to update the answer to this question in particular. A 2000 lumen LED tube will appear to put out a lot more light than a 2000 lumen fluorescent tube. This was explained by a guy who's a lighting engineer on another forum I frequent.

A fluorescent tube emits light all the way around its surface. With a normal white painted reflector, the generally accepted rule of thumb is that only 70% of the lumens end up as actual usable light in the work area. The reflector has less than perfect reflectivity, and the tube itself blocks a portion of the light that shines upward from being reflected back down to the work area.

But, that's not the only issue with fluorescents. The lumen rating is based on a set of test parameters where the ballast is "perfect" for the tube, but in the real world, production ballasts have variations and inefficiencies that result in the typical tube putting out only about 90% of its rated lumens. At that point, the useful light is roughly .90 x .70 = .63, or 63% of the rated lumens.

And, finally, the high operating voltage of a fluorescent creates a charge that attracts dirt to the tube surface. Once the tube has been in operation for a relatively short time, this dirt will combine with the other light reducing factors above to reduce the actual usable light at the work area to something in the neighborhood of 50 to 55 percent of the rated lumen output.

Per the engineer, all the above are well known factors and they have been included in professionally done lighting calculations for years. OTOH, LED tubes don't rely on the use of reflectors. The light is aimed downward, usually with a 120 degree spread. Standard cheap strip fixtures with no reflector will work just as effectively with LEDs as any high dollar fixture with a reflector. The voltage isn't critical. You can feed a bypass tube with any voltage from 120V to 277V and it'll work just the same. And the LEDs don't develop the dirt attracting charge like the fluorescents do. Of course the LED tubes aren't perfect, and they do have their own inefficiencies, but they're minor as compared to the factors that reduce the usable percentage of light at the work surface when using fluorescents.
 
Interesting reply. I did upgrade to the LED bypass tubes 8ft. frosted 5000 white and like them but don't see a lot more brightness.
 
i was buying a case of bulbs a year. even with that the fluorescent tubes would be down to 50% in no time. slow death so you really dont notice as much. when i run out of tubes i will switch my booth over to led . there's just no comparison .
 
Just remember to look at lumen spec. I've seen 4' leds from 1600-2200 lumens. And more lumens = more watts.
Don't need top dollar brightest but definitely don't want cheapest dim ones.
4000k is pretty much white like most stores, 5000k a tad closer to daylight. Guessing daylight's close to 6000k.
 
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