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Anselm Havu

Exposing When Using Color Effect Filters

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Hi all,

 

I was wondering how one would go about exposing or even using color effect filters like color gradients, Coral, Antique Suede or Day for Night optical filters while shooting on a digital camera and delivering in color.

 

For example, say that you are using an Antique Suede.

  • Wouldn't depriving the sensor of blue light be very destructive to the raw image? To my understanding the blue channel displays the most noticeable noise the most often. If so, how would you combat this?
  • What are the advantages of doing such an important color decision in camera rather than in post apart from the "stops people from messing with your image" argument? Are there any clear optical or overall quality differences?

Thanks in advance!

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I wouldn't over think the technicalities on color channels. The same was true for film, to a certain extent that you could over-expose (or under) certain color layers-- and in truth that's part of the effect.

 

As for the advantage; well 1, keeping control of your images is VERY important. It's often easier and more consistent to throw a filer on (costs less) than time spend in post doing it. Optically, any glass will chance the optical characteristics you're recording. You can see how the effect is being rendered "In real time" (granted you can kinda do this with a LUT; but you'd need to have made that LUT before hand and keep it around forever in-case of reshoots). If you have a reshoot, you don't need the LUT/correction you made on set, you can just use the same filter (will be pretty close). Many filters come in varying densities. You can see how exposure choices can change the effect on the day (or better in prep). And most importantly, because, well, you really want to do all you can to make the rest of the film process easier for those down the line. What I mean is, you have limited time and budget for EVERYTHING on set and so often the job is really about finding that happy medium where you choose the most effective path to the look you want.

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I wouldn't over think the technicalities on color channels. The same was true for film, to a certain extent that you could over-expose (or under) certain color layers-- and in truth that's part of the effect.

 

As for the advantage; well 1, keeping control of your images is VERY important. It's often easier and more consistent to throw a filer on (costs less) than time spend in post doing it. Optically, any glass will chance the optical characteristics you're recording. You can see how the effect is being rendered "In real time" (granted you can kinda do this with a LUT; but you'd need to have made that LUT before hand and keep it around forever in-case of reshoots). If you have a reshoot, you don't need the LUT/correction you made on set, you can just use the same filter (will be pretty close). Many filters come in varying densities. You can see how exposure choices can change the effect on the day (or better in prep). And most importantly, because, well, you really want to do all you can to make the rest of the film process easier for those down the line. What I mean is, you have limited time and budget for EVERYTHING on set and so often the job is really about finding that happy medium where you choose the most effective path to the look you want.

All that makes sense to me. Thanks for your reply!

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The blue information would only show grain / noise from underexposure IF you tried to add blue back into the image, but since the whole point of using these warming filters is to make the image warmer, odds are that you'd just let the blue information stay where you exposed it.

 

However, since with a digital camera, the blue channel is cleaner in daylight-balance and in film, the yellow layer (for blue information) is slower / finer-grained with daylight-balanced films, I'd work from a base of daylight if possible before adding the warming filter on top of that.

 

If you're using a digital camera, you can even try setting the color temperature to something higher than 5600K, like 7000K, for a warm look outside and then you could use a weaker Antique Suede or whatever on top of that.

 

But in general, I wouldn't worry too much about blue channel noise if you plan on having desaturated blues anyway.

 

Also, if you're worried about noise, it cuts both ways -- if you shoot neutral and add the warmth in post, you are basically pushing some color channels harder to shift the image away from neutral, risking some noise. If you shoot warm and leave it warm in post, your noise per channel should be the same as if you shot neutral and left it neutral because basically you haven't altered any of the levels in the channels.

 

I do often lean towards the idea of getting halfway there to the look in camera and finishing it in post -- so make it warm in camera and then make it even warmer in post if you decide it is necessary. But it's really a judgement call, sometimes you just need to go for the look you are imagining, especially if being stylized is the goal anyway.

 

Now if you are doing blue screen work, then you shouldn't add a heavy warming filter that corrupts the blue information. Indoors, you'd light the blue screen neutral-to-blue and light the foreground warm if that's what you want.

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