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Why use in-camera filters for changing white balance (say 200T stock in daylight) instead of simply changing the printer lights in post? (Before DI)


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In practice, it was not a big deal to correct out the blue cast, but your printer lights were very skewed with the blue printing at very high numbers.  If you had an accidentally overexposed shot, there could be a chance of hitting the 50 light value for blue and not being able to shift colors anymore without retrimming the printer, but that was pretty rare.

The image of the corrected shot wasn't exactly the same as if you used the 85 filter, skin tones might look a bit paler for example.  You might also have more blue haze in daytime shots from the lack of UV filtration that the 85 filter also provided.

I did several features without the 85 filter on tungsten stock in daytime, but they tended to be winter movies or horror movies where I wanted to leave the image timed on the cool side with less saturated reds. In other words, I wasn't going to have to try to time the scene warm when it was cold on the negative.

It also depends on how many filters you plan on using in the mattebox, if you don't like stacking glass and you plan on always having a diffusion filter, for example, then at least for day interiors, it might be better to avoid the extra glass of an 85 filter that could cause double reflections.  Outdoors where likely an ND would be required, it makes less of a difference, you might as well use the 85ND combo filters.

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I read somewhere, which of course I cannot find, that if you don't correct tungsten balanced film while shooting outdoors, you cannot recover greens properly. Is that correct?

It's also worth pointing out that you should use correction filters on digital cameras, wherever possible. Especially if you're shooting highly compressed formats. The small effort will be worth it.

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Sort of the opposite, many cinematographers felt that greens plants outdoors in daylight were rendered more richly if you shot without the 85 filter on tungsten stock, particularly John Alcott said this about shooting “Barry Lyndon” and “Greystoke” this way, and the greens are very nice in those movies.

And there is even less reason to use an 85 filter on a digital camera since sensors have a native bias towards daylight balance (the blue channel has to be pushed to balance them for tungsten.) Some people used to advocate blue filters for shooting in tungsten light for this reason, like with early Red cameras, but as noise has improved, this has become less necessary though you’d still have a cleaner blue channel if the light is closer to daylight.

You should record close to a balanced image by selecting the correct WB on the camera if recording to a compressed format with a low bit rate and 4:1:1 color subsampling just because you don’t have a lot of flexibility after that to make heavy corrections.

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