Color of CFL bulbs

[Zach in Israel]

I have a few CFL bulbs that say on the box they are "Daylight" color. Is there any easy way to figure out how accurate the color is and if it will leave a weird color cast on my film? I guess I could just load some slide film into a camera and take an exposure of a white piece of paper under the bulb and see how it comes out. Is there any other ways to do it?

 

[David H. Bebbington]

I have a few CFL bulbs that say on the box they are "Daylight" color. Is there any easy way to figure out how accurate the color is and if it will leave a weird color cast on my film? I guess I could just load some slide film into a camera and take an exposure of a white piece of paper under the bulb and see how it comes out. Is there any other ways to do it?

There are such things as color temperature meters - if you don't have one (I don't either!), you can probably assume that a "daylight" bulb is about 5500 Kelvin, which means color pix with no filter would be correct but would probably look better with an 81A filter (slight warm-up). I have other CFL bulbs which are sold to counteract Seasonal Affective Disorder (SAD) - these bulbs have a color temperature of 6400 K and I use an 81D filter with them.

Regards,

David

 

[David A. Goldfarb]

Helen Bach was nice enough to lend me two of her color temperature meters, and I tested the CFLs I had on hand. The "daylight" bulbs were indeed balanced for daylight on the red-blue scale but still needed about 30M to correct the green cast. The other bulbs we had were balanced for tungsten on the red-blue scale, but also needed about 30M to correct the green.

 

[MikeSeb]

I find that "daylight" bulbs still somehow look sickly. Guess it's because, unlike daylight--which is a nice mixture of the whole spectrum, blended by nature--fluorescents emit in a narrow frequency range and are rendered "daylight" by filtration and other trickery.

 

[CRhymer]

CRI (Colour Rendering Index) is also important. The higher the number the better. The better bulbs are getting - well - "better", but there is still a ways to go.

Cheers,
Clarence

 

[AgX]

David,

If you have at two-sensor colour-meter a light source consisting only of two lines rather than a continuous spectrum might give a reading for perfect daylight.

A three-sensor meter would be better, better even would be, as Clarence said, to resort to the CRI, best would be to look at the very spectrum of the lamp as indicated by the major manufacturers in their catalogues.

 

[JBrunner]

Cfl's are usually have a dis-continuous spectrum, no matter how they are balanced. They generally include a magenta and green spike, the amount of which varies from lamp to lamp, no matter how they are balanced. I have found them problematic for enlarger use, although Ole has reported good results.

For use with film you could try what is called a "flourofilter"

http://www.tiffen.com/dfx_flourescent_ig.html

....or you can gel all light sources to a uniform green and and correct back to normal after the shoot, which is the procedure I use in mixed lighting situations like when I have to shoot large areas in supermarkets with a foreground subject that I need to light. It's much easier to make my lights match the prevailing light in those kind of situations, and apply a uniform correction after the fact.

 

[ZachInIsrael]

I will give the light a try, two exposures of 35mm film is cheap enough to be worth trying. If not I was going to get some halogen work lamps for something else, maybe I will try those with a filter or for B&W.

 

[John Koehrer]

The halogen lamps should be a 3200k and will work fine with B&W. For color and halogens you can correct with an 80A filter.

 

[JBrunner]

The halogen lamps should be a 3200k and will work fine with B&W. For color and halogens you can correct with an 80A filter.

With B&W stocks you will need to consider a speed adjustment when using 3200k lights because many stocks are less sensitive when being exposed to such a wavelength.

I believe the OP was referring to color stock. If it is indeed B&W load up the cfl's and bang away.