Spreading a colored gel over a b-board

DavidSloan · September 25, 2004

I have to light a staircase in a dark park. It's a suspensefull scene and the director is working with the theme of red. This is a narrow staircase which leads to a parking lot at the bottom of it. On the left there is a plain wall and on the right there is a tennis court which at the head of the staircase is on the same level but as you go down the steps we get below it. I was thinking about rigging a b-board up high, and at an angle, from the tennis court with a 2k open face shooting right at it. I was also going to spread a red gel over the b-board to give off red ambient light. I guess the question is, is it okay to wrap a gel over a b-board like that..I've done it before with satisfactory results. And I heard that red gels somehow mess with your light readings...is it true, and if so how do I solve that problem?

Kevin Zanit · September 25, 2004

I would gel the light, not the board. You also may want a light with a little more punch because of how much light you will loose through the red gel.

I have never had issues with exposure in red light, just focus. Because red is the last layer on the film, it is prone to some slight focus issues (assuming your shooting film).

Kevin Zanit

DavidSloan · September 25, 2004

Shooting S16mm.

I never heard of the focusing issue. That's a scary one. Is there a way to avoid it or is it a pure gamble?

Thanks

Phil Rhodes · September 25, 2004

Hi,

I understood that the issue with focussing red light is a wavelength thing. Different wavelengths diffract differently, and the setup of the lens is right in the middle - while the red is at one end. If this is correct, eyeball focus in the viewfinder will still be accurate.

Phil

Michael Nash · September 25, 2004

The problem with red light is that it can LOOK out of focus, even when it's sharp. Just keep this in mind if the scene has only red light, and try to provide some high contrast edges for your eye to grab onto.

I've read that it's better to underexpose saturated reds, partly due to the spectral sensitivity of meters and partly because of the way it renders on the negative. That said, I've never had a problem exposing it normally.

Any gel you put on a beadboard DOUBLES the effect of the gel, both in stop loss and saturation of the color. The light has to pass through the gel twice before it reaches the subject. You also get "gel bounce," or hard specular reflections off the glossy surface of the gel.

DavidSloan · September 25, 2004

Any gel you put on a beadboard DOUBLES the effect of the gel, both in stop loss and saturation of the color. The light has to pass through the gel twice before it reaches the subject. You also get "gel bounce," or hard specular reflections off the glossy surface of the gel.

I had no clue, about that. Thank you. I once did a shoot where I had to light a guy in a cell and give him an orange glow. There was no way to light him with an instrument, so far as I could see, so I taped a b-board to a wall and layed an orange gel on top of it. The image came out great. Maybe that's what you call beginner's luck! :D

Laurent Andrieux · September 25, 2004

Maybe but what Michael says is right, anyway. Thelight first passes thru the gel, then reaches the bounce board, then is reflected and passes trh a second time. You can always make the experience that a gel looks more dense if you put it on a piece of white paper than when you look thru it.

Fredrik Backar FSF · September 25, 2004

Hey. there. have found that heavy filtration messes with the light meters making them give strangfe readings. Leaning u towards under exposure unfortunately. Have no way to go around this though....

Good luck anyho.

Laurent Andrieux · September 25, 2004

The best would be to make tests before shooting : key-light and gel tests + focus tests with Foucault charts in the determined gelling...

DavidSloan · September 25, 2004

Is red the only gel that gives cinematographers problems? Are there other colors that I should be concerned with?

How about putting a light red filter on the camera do I face the same problems?

For those who have shot with red gelled lights, could you tell us what the shot was, and what specific problems you experienced? Also, did the director kick your arse! :lol:

Sam Wells · September 26, 2004

" You also get "gel bounce," or hard specular reflections off the glossy surface of the gel."

Which I like to do sometimes.

-Sam

Laurent Andrieux · September 26, 2004

But I agree that it's best to gel the source... Putting a filter on the camera would give a red look to the entire image, why not if that's what the director wants. If he only wants the caracter to be sort of redish, may be make-up could help ?

DavidSloan · September 26, 2004

A DP friend suggested to use a heavy diffusion with the red gel...he claims this helps to "mute" the red, a bit. Supposedly the red "bleeds" and looks muddy if not handeled correctly. Can anyone elaborate on this?

Like Michael, he also recomends to underexpose a bit...about a 1/3rd of a stop from incident reading. I think I definitely have to do some tests with this friggin red gel. Oh these demanding auteurs :rolleyes:

(I should know I'm one myself :D )

Laurent Andrieux · September 26, 2004

Good one ! please tell us what these tests go like...

Great to have the others work for you ! :D

September 27, 2004

When people say "Gels" here are they referring to an actual coloured solution? Because the only "Gels" I have seen are colours acrylics.

Phil Rhodes · September 27, 2004

Hi,

Using diffusion with a strong colour would only mute it if there were other colours in frame; you'd be mixing them together for reduced effective saturation. That might stop chroma clipping but it would make the colour appear to "bleed" more. It might make it less obvious if you had focus problems with deep reds, though.

Phil

Michael Nash · September 30, 2004

When people say "Gels" here are they referring to an actual coloured solution? Because the only "Gels" I have seen are colours acrylics.

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We're talking about sheets or rolls of heat-resistant polyester that are dyed different colors. You know, the stuff you put on lights! :P Don't confuse actual gels with colored celophane like you might wrap gift baskets in -- it'll burn and melt.

Some manufacturers refer to gels as "filters," which is correct but can be confused with lens filters. So most people call them gels.

Pick up a swatch book from the major suppliers; Lee, Roscoe, GAM, Formatt. Just looking through them and comparing them can be educational.

Laurent Andrieux · September 30, 2004

These gels can be considered as films, but they're never called so. The thing is in french we call them the same as the substract for photo-sensitive components : gelatine. Were they made from gelatine (with pigments inside, instead of photo sensitive silver components) before polyester was introduce ? Does anybody know ? what support would have they been put on, then ?