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Overexposing film for more detail.


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Hello! Firstly,I would like tho appologise for my bad spelling, since english is not my native language.

I am planning to do my first project on s16mm film in near future. Since it would be my first experience shooting motion picture film, i have been scouting the depths of the internet for tips, and i often come across a recomendation to overexpose by 1-2 stops, to bring out the detail in the shadows, since negative film can retain highlights much better. So i would like some other professional opinions on this. Is this a common practise? What is the lattitude of motion picture film (Kodak 500T for example). One dp friend that i know told me that its safe to assume that film wil retain information within 3 stops of overexposure, and 2 srops of underexposure. Any opinions on this?

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Film negative does record information on a gamma curve -- basically at the extreme ends, the amount of density increase relative to exposure amount starts to flatten out (lower in contrast). However, if the stock has almost 15-stops of dynamic range, overexposing doesn't increase that, you are just trading highlight detail for shadow detail. But it is true that with the latitude for bright highlights, often it isn't a bad idea to give the negative more exposure to improve the shadow information.

But within limits -- I think a 1-stop overexposure is more than enough if you are simply trying to get a normal image but with cleaner shadows. Too much overexposure and your negative gets very dense and it takes more light for the scanner or telecine to push through it and sometimes you can end up with electronic noise in the highlights on some systems.

Also keep in mind that if you are overexposing to reduce grain, the large grains in the stock are what determine its speed -- 500T has larger grains than 200T. Overexposing just exposes more of the smaller, slower grains in between the larger ones, giving the grain structure a tighter appearance. But the large grains are still there, they are the first to react to light. So you may be better off switching to 200T rather than overexposing 500T by rating it at ISO 200 if grain reduction is your main goal. However, the overexposed 500T would have more shadow detail.

Personally I find that rating 500T at ISO 320 is generally enough to improve the look of the stock in terms of grain and shadow detail. Rating it at ISO 250 would be about the most I would do (I did a whole feature where I rated 200T at ISO 100 but it took a lot of light!)  But that assumes you aren't prone to accidentally underexposing a lot.  Everyone finds a method of rating stocks that works with their natural tendencies while giving them the consistent results they want (assuming they are consistent in their tendencies...)

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David is spot on of course. 

I generally over expose around a stop if I need it, but a lot of times I can't over expose. I'm if anything running out of exposure indoors in limited lighting. If you can "over expose" in a dark scene, that would be wonderful, but it's just not possible most of the time. 

For me, rule of thumb with any shooting is to make sure it's lit properly first. Don't rely on over exposing to see shadows, rely on lighting to insure you have good shadow detail. 

The more you over-expose, the more there will be a slight color shift as well. So you have to be very mindful about that, don't just over expose because you will hate it in post to deal with it. 

One stop is about all ya need. 

Some people under-rate stock to flatten it out a bit. It's very common with 250D, it really flattens out the image, makes it less contrasty, but you've gotta use much flatter lighting. 

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On one shot on a Super16 short film, the A.C. forgot to stop down the lens on an exterior, but for production reasons that was the required take. The over exposure had to be compensated for in both the interneg and the 35mm print,  the shot held up, but that's more of a rescue than a method that should be used.

One stop over exposure should be enough.

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