Gray Card in the beginning of each scene theory

Jae Solina · March 31, 2016

Good morning! I am currently reading the "Cinematography: Theory and Practice: Image Making for Cinematographers and Directors" and came across information I cannot quite understand.The book says that "the proper way to shoot a gray card reference is as follows. For a tungsten lit scene, position the gray card so it fills all or most of the frame. Have your gaffer light it with a unit that is near 3200 kelvin. The light should cover the card as evenly as possible with a single light." What would be the point of using the gray card as reference if you arent using the lights/environment of your scene and is using a separate light to light the gray card? Am I missing something? I want to learn how to shoot the gray card in the scene so that i can use it as reference later in davinci. Apologize for my english I am foreign. Thank you.

David Mullen ASC · March 31, 2016

The grey card is to provide the colorist or timer a "boring" neutral reference that does not need to be interpreted artistically, the exposure is obvious to anyone. If you just had a scene without the grey card and it was lit to be very warm and dark, the colorist would not know what levels to transfer the scene at -- he could make a guess or he could start by neutralizing the warmth and making it white, and brightening the scene to be a "normal" level.

But if he had a normally or correctly (for the ASA rating you wanted to use) lit grey card at the head, lit for whatever you wanted to be neutral, then he could balance the transfer for the card and when the warm, dark scene popped up next, he would know that it was intentionally warm and dark. If the card was exposed normally but the scene was underexposed by one-stop to feel darker, then that should be clear to the colorist after he balances the transfer for the grey card.

I say "neutral" because there are times when you might want the grey card lit with something other than "white", to get the colorist to shift the overall color bias of the footage that follows. A classic example is when you are shooting under a lot of uncorrected fluorescent lights in a grocery store and you want to colorist to time out the greenish color cast, so you'd shoot the grey card under that lighting (conversely if you wanted to keep that cyan bias from Cool White tubes, you might want to shoot the grey card under a normal 3200K tungsten light).

Another example would be to shoot the grey card in a tungsten-lit scene, but with a 1/4 Blue gel on the light for the grey card - when the colorist sees that blue-tinted grey card and corrects the blue cast back to neutral grey, the following scene after the card will look warm because he had to add warmth to the card to get rid of the blue. So this is one way of getting a warm tint added to the footage without using warming filters. It's similar to white balance tricks in a video camera, white-balancing the camera to a light blue card so that the scene looks orange-ish.

Jae Solina · March 31, 2016

Mr. Mullen thank you once again. When are you writing a book? Would love to read it. Very nice examples. That makes so much sense now. I think i might be misusing my grey card. What I usually do is record the greycard in front of the actors face then make that neutral in post by adjusting raw wb and tint and then add my taste of color afterwards. Its difficult sometimes to white balance without a greycard especially when using output 3d luts for they have built in color. How does the pros do it? Record in raw, have an onset monitor with 3dlut capability, light the scene so that they will get exactly what they see then in post use the same lut they used in the monitor on set?