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Fluorescent with gells, as good as halogen?

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Ben Edwards
Fluorescent with gells, as good as halogen?
on Apr 7, 2010 at 9:16:19 pm

I have been trying to get my head around why video shot under florescent does not seem to look at good as video shot under halogen/tungsten (when white balanced) and realised maybe I should use gells to change the colour temperature.

I did a search in this forum for 'Fluorescent gells' and got nothing back, so either I have totally lost the plot or maybe I am onto something.

Is it something to do with the fact that even if you white balance properly when you use gells you will get a different image depending on the gell. I guess a red gell will make reds brighter as they reflect more light on reds (or have I got this the wrong way round).

So continuing this train of thought there should be a gell that you should use with florescent light for interview that (for example) warm thee image up a bit without looking yellow. I would like to use florescent as it used less power and produces less heat but will that be to the detriment of the image?

I have invested in 'Lighting for Digital Video and Television' by John Jackman (2004) and when it arrives am hoping this will answer some of my questions but any advice/links would be gratefully appreciated.

The final thing I should add is am am trying to get as truly portable set-up that I can carry but this may be asking a little too mutch.

Regards,
Ben


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john sharaf
Re: Fluorescent with gells, as good as halogen?
on Apr 7, 2010 at 9:33:52 pm

Ben,

Not sure if you mean to use the "practical" fluorescents in the ceiling or "Kino Flo" (or equivalent) photo grade lights?

To use the overheads to illuminate a portrait, as in a typical interview shot, the lights are not in the ideal place relative to the face. What happens is that they top-light the nose and cheeks and not the eyes, creating what is often referred to as a "raccoon eye" effect. They can however be white balanced to create an almost accurate color. I say almost because they are a discontinuous light source with a green spike in particular. Fluorescent gels, such as they are, are meant to either eliminate the green spike (minus green), or add the green spike to tungsten balanced lights that is then white balanced out.

Photo grade fluorescents are tubes that are designed to minimize the green spike and be either 2900K, 3200K or 5600K in color. In addition they are often coated with a plastic cover to control the spilling of glass when handled oughly and broken. In addition, Kino Flo ballasts make the lights flicker, or go on-and-off at a higher frequency both to increase there output and to make them flicker-free at various shutter angles and frame rates.

It's been mentioned many times here in this forum, but a rather elegent solution to shooting in a practically lit fluorescent interior, like a school or hospital, is to borrow some of the 4' tubes that populate the overheads and use them on the floor in 4' Kino Flo instruments; now every light is the same color and the floor lights can be used in a conventional portrait lighting location (into the eyes). Simply white balance and voila. The final touch would be to turn of or flag off the units directly overhead to eliminate the top lighting on the subjects nose.

Kino Flo units, especially the 4'Fourbank is a great portrait light, by virtue of it's large size and soft quality.

JS



JS







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Ben Edwards
Re: Fluorescent with gells, as good as halogen?
on Apr 7, 2010 at 10:03:27 pm

Thanks for the reply, I meant the florescent bulbs sold for video and photo work of the colour tempritures you mentioned.

what I was wondering was is it agood idea to put gells on them to warm up the colour a little.

Ben


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john sharaf
Re: Fluorescent with gells, as good as halogen?
on Apr 7, 2010 at 10:11:15 pm

Ben,

Using gels "wastes" some of the output of the light. I prefer to use 2900K Kino Flo tubes and set the camera at 3200 preset. This equates to using a warming gel like 1/4CTO on the light without diminishing it's output.

JS



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Richard Crowley
Re: Fluorescent with gells, as good as halogen?
on Apr 16, 2010 at 3:19:37 am

Or use a blue-tinted "white balance" card to "cheat" the camera warmer.

OTOH, does "not seem to look at good" have a better definition? Exactly WHAT doesn't seem to look as good? Could it be CRI and not color temp?


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