color of light question

[mark]

What color will a red or blue or green led light be on color film? Will they photograpgh as these colors or would I have to filter for each one to keep their color?

 

[Nick Zentena]

Don't know about LEDs but

Blue will look yellow on the negative.

Or do you mean the print? Or something lit by the LEDs?

 

[Donald Miller]

It depends on the type of film...if transparency the colors will be the color of the LEDs and if negative film they will not be...filtering should not be necessary.

 

[mark]

I mean in the final print.

Donald, Why would they not be the same with color neg film?

 

[htmlguru4242]

I believe that Donald is talking about the colors appearing on the physical strip of film. With color negative film, the colors would be inverted on the strip of film, as it is negative film. On slide film, the colors would be correct.


The LEDs, if photographed, will be of the correct color (obviously accounting for the slight inaccuracies that occur with all color films) on the print. Whatever color you see will be close to what will be on the print.

 

[mark]

Cool, thanks guys, found a neat idea and want to try it out.

 

[nworth]

Green, yellow, orange, and red LEDs are narrow line width sources. They should reproduce fairly accurately on color film, although the brightness may not be the same as you see with your eye. You can make a fair guess by looking at the published sensitvity curves for the film. Blue, violet, and "true green" LEDs have braoder spectra. They will still probably look OK, but you could get some funnies. White LEDs are usually a combination of a blue LED and a yellow phosphor. The emitted light is really quite blue. Most produce a decent white source light for daylight film, but some show maked dropouts in certain colors.

 

[127]

You'd need to combite the spectral response of each film layer with the spectra of the LED. I'm not at all convinced that narrow band emitters will record at all well...

An led which emits only light in one of the films spectral bands (ie affects only one layer) cannot be recorded accuratly - the film only records the intensity FOR THE LAYER.

There's no way to differentiate between two different LEDS that trigger the same band to the same extent. If a green led only triggers the green layer, then there's no way to know WHICH green it was, just that it's green and how bright. It'll be green on film, but not the same green. Any LED that's completly within the green band would look exactly the same on film.

Typically we get away with it as real world sources have broad spectra, and trigger all three layers to some degree.

Ian

 

[htmlguru4242]

Mark, what exactly are you trying to do here with the LEDs?