How high should a fluorescent bulb's CRI be to make great pictures?

[Stephen Pruitt]

Hi there. . .

I was thinking of trying to build some Pruitt-flos for a low-budget feature shoot. The bulbs (compacts) I was thinking of using have a CRI of 82. Is that a sufficient number for great footage? Or do I need something up into the 90s?

Thanks very much.

Stephen

 

[Barry Green]

82 is pretty bad, and unless you're looking at Kinos or other quality brands, it's hard to trust those numbers anyway.

Furthermore, you'll need a high-frequency electronic ballast or you'll run into the same wavy scrolling lines issue that a magnetic HMI causes.

 

[Richard Andrewski]

Its a bit more complicated than that. The higher the CRI, the lower the lumen output and the more you have to overdrive the bulbs to try to get them to output. Achieving a CRI 90 to 95 flo bulb is not that big a deal for a factory with the right rare earth phosphors and the technical know-how. However, this involved taking the green spike out of the bulb and it is unfortunately that spike which gives the bulb its kick in light output as green is the color our eyes are most strong in reacting too. We settled on CRI 87 to 90 range as a good compromise on CRI and bulb output when we were making the Cool Lights 55w bulbs. The Home Depot N:Vision CFL bulbs are around CRI 82 and many have used them with good results. Are they perfect? No, but for the price they aren't too bad either. They're available in 3500K or 5500K.

 

[Policar]

The NVISION lights definitely have a visible green spike, but it's not egregious. The 3500Ks are more expensive than the 6000K or 2700K... Surprisingly, I think these lights (unlike many compact flos) are flicker free!

I'd use them but maybe with a magenta -1/8th and I would definitely take kinoflos before them under almost any circumstances. The only issues with kinoflos is their size; compact flos you can put in budget busters or tape to things and it's flexible. Also, avoid the 2700K. Too orange.