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Are effects gels meant to be used with tungsten or daylight sources?


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I'm interested in some effects gels such as 183 Moonlight blue, twilight blue and a few others, the light that I want to use it with (aputure 300d mk2) is daylight only, not sure what source you meant to use it with to get the desired 'moonlight blue' effect.

 

Trying to find the answer to this everywhere but no luck.

Wondering if anyone could help, thanks!

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The white balance of the light should match the white balance of the camera to get the intended result from the gel. 

So if your light is 5600K, set your camera to 5600K. If your light is 3200K, set your camera to 3200K. 

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I’ve always felt that effects gels work best with tungsten sources, mostly because of their origins in the theater, where tungsten sources were the norm. There’s also the problem of using gels on discontinuous sources, which can have unexpected results. That said, these days, as long as your white balance matches your lamp, as Satsuki says, it shouldn’t make too much difference.

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There are some specific effects that only really work with certain things. If you want a deep, powerful blue, like Lee's 181 Congo Blue, then it's vastly easier - certainly much, much more efficient - to drive it with HMI than tungsten, and you'll discover that the vast majority LEDs actually don't contain any Congo Blue so you can't really filter them for it. It's deeper than most blue LED emitters, deep enough to create something like a blacklight effect. It's also frequently out of gamut for both cameras and monitors which can create ugliness.

The other thing to watch out for is what happens if you put very deep longwave (red) gels on tungsten, as for a darkroom scene or something like that. Most gels seek to pass IR to reduce overheating, so the sheer amount of IR pollution can become a much larger, more noticeable proportion of the whole than without the filter. Often this manifests as everything looking desaturated and more purple than red.

These are pretty edge cases, though, and usually it's straightforward. I would reiterate Stuart's note that weird light sources, including LEDs, can have unpredictable results, even quite good LEDs. You might have a quality LED light that matches a real tungsten light well, but they may not react the same way to gels.

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1 hour ago, Phil Rhodes said:

weird light sources, including LEDs, can have unpredictable results

One example of this is using CTO on HMIs. Older globes can have a pronounced green spike which is often largely hidden by the blue in the lamp. When you put CTO on it, the blue frequencies are cancelled, and the green suddenly becomes very visible. I've been told in the past that one reason for this is that CTO is designed to convert Daylight, not HMIs. LEE actually make a specific gel to do this (LEE 236). Similar things can happen with cheap LEDs

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  • 2 months later...
On 1/22/2021 at 6:09 AM, Stuart Brereton said:

One example of this is using CTO on HMIs. Older globes can have a pronounced green spike which is often largely hidden by the blue in the lamp. When you put CTO on it, the blue frequencies are cancelled, and the green suddenly becomes very visible. I've been told in the past that one reason for this is that CTO is designed to convert Daylight, not HMIs. LEE actually make a specific gel to do this (LEE 236). Similar things can happen with cheap LEDs

That's a wonderful bit of info. I noticed that effect when CTO-ing a window and punching a 4k HMI through it. I assumed it was due to the lamp's age, but an inherent spectral green spike in the metal-halide mix makes a lot of sense.

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