Problem with gels

Kev M

Kev M

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I've got an idea where I need to create an orange colour cast simulating tungsten lighting but using flashguns. I had a quick play around last night fitted a CTO or half CTO gel over my flashfired away until my exposure was 'right' and the shot had a nice orange glow to it (WB was set to sunny). The light was bouced off the ceiling as it's going to simulate a room light.

What I then wanted to do was under expose this light as I'm going to be adding a simulated reading lamp at a later date which needs to be brighter than the main light (again using flashgun). What I then found was that not only did my picture get darker but with each stop down of the aperture the colour cast became less apparent to the point where it almost looked like there wasn't a gel fitted at all.

Is there a reason for this and if so can anything be done about it or is it just one of those things?

Shifting my WB around isn't an option either, I'm doing test shots with my digital camera but the final images will be shot on film so I need to set this up with a daylight WB.

Cheers,
Kev
 
Hi. Not quite clear yet as to exactly where you're going. If you're happy to answer a few questions, I'll try to throw some light on what's happenning.
First thought, If you are going to end up using film then I would suggest some test shots with film as digital and film will see the orange differently. Which film are you intending to use ? daylight or tungsten ? tranny or neg ?
When you underexposed the digital shot, were you noticing the loss of colour in the darkened picture or did you increase the brightness of the picture in the computer and saw the colour loss there ?
 
I'll probably use provia or astia in the end (daylight, tranny). The shots never made it off the camera soo
I was looking at an underexposed shot on the LCD.
 
Kev, first off - you can alter "white balance" with film. It is called using a colour correction filter, that is what we used to do before the days of digital!

If you stick a warm up in front of the flash, it will match the tungsten from room lights (81B) so everything will be bathed in the similar coloured light - not exactly the same because without a colour temperature meter your tungsten lights could have lost some colour or be a bit darker...but average is 81B.

that is ther easiset way to do it with film....to match this with digi, warm the white balance up. All white balance is is a set of colour correction filters on the inside of the lens (in the camera) instead of on the outside in front of the lens or in front of the flash.

maybe that will get you thinking along the right lines...trouble is, in writing this I have now forgotten the content of your post! I'll have to go back, have another read and come back again.......now, what was it I was doing?:thinking:
 
Remember, as you underexpose a gelled flash, the STRENGTH of the colour increases - over exposing a gel washes the colour out of it - basically you overpower the colour cast.

If you are going to underexpose your flash...get it right setting first without the gel, then use a lighter warm up gel to add the cast....try a couple of different ones to see which matches your idea best.
 
Hi. I suggest you place a Full CTO over the flash to create the "tungsten" look. My technique would be first get both flash sources in place, the room light and the reading light. Get the power/exposures of both to be the same and correct from the camera exposure point of view. Then place the gel over both the flashes, this will reduce the light by one stop. This slight underexposure may enhance the orange look. Bracket the final exposure.
To reduce the room light, as you have mentioned, I would suggest a 2 stop lighting filter placed over the "room" flash.
Good Luck.
 
You can adjust the room light by either dragging the shutter (brigtens the room, burnsout the warmth from tungsten lights, increases shadow detail) or to darken the room, shorten the exposure a tad.

In either case, the flash exposure will be the same.
 
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