Re: Fluorescent Bulbs by JOHN SHARAF on Mar 12, 2002 at 11:18:33 pm
Normal household and industrial flourescent light bulbs go on and off at exactly a 60 cycle rate so that they do not "flicker" to the eye due to persistance of vision effect nor do they flicker in an NTSC video photography system because they are in a multiple of 1/60th of a second.
Conversely, if you were to use your NTSC camera in a country (like Great Briton) where the electricity cycles at 50 cps the effect would be an extreme flicker!
Re: Fluorescent Bulbs by JOHN SHARAF on Mar 13, 2002 at 12:09:31 am
All flourescent globes are considered "discontinuos" light sources. That is that they do not make a straight line in a spectrograph or reproduce all colors equally. Flourescents in particular spike higher in the green responce. In normal use, the human eye/brain corrects this color aberation away, but unfortuneatly photo imageing for stills, film and video does not.
There is a pinkish filter gel known as "minus green" which when applied in the proper amount (1/8, 1/4, 1/2 or full) allows you to whitebalance and then expect an almost full and accurate color reproduction on tape (or film with proper timeing or cc in post).
The photo grade flourescents in 2900, 3200 and 5600K make the necessary correction so that additional minus green filtration is not necessary. That's one reason they're more expensive than a "normal" tube!
Alternately you can use a "plus green" filter gel on your tungsten lites which you add to the predominantly lit flourescent scene and then white balance away the overall green cast.
One final thought is that you should be aware that there are many different flavors even amoungst the normal tubes, such as warm white, cool white, etc. and even in the same location or room various different colors are often mounted. It is in the lighting photographer's best interest to remove the plastic diffusers and look carefully at the nominclature on the tubes and replace those that are necessary to at least have a uniform color to which you apply the proper correction. You'll also find that by leaving off the diffussors during your shoot you'll get more light output from the overhead units!
Re: Fluorescent Bulbs by Chris Sorensen on Mar 13, 2002 at 12:35:18 am
Actually, the reason I was asking is I found some fluorescent work lights on a stand (like the halogens that some people use) that use fluorescent standard base bulbs.
http://www.designersedge.com/worklights.html (bottom of page)
I was thinking of using them as low budget lighting on a DV short since they'd be cool temp, low power and soft light. They come with 4100K bulbs. Didn't know if switching would make the green color thing better.