Hello!

I need some advice on this. When using a gray card to set exposure, suppose you're shooting at a distance. For example, suppose the subject is 50 feet from the camera. I assume the proper thing to do is to have an assistant hold the gray card where the subject would be (50 feet away) and then take the reading from that distance. Is that correct? I would assume standing close to the gray card would give an inaccurate reading...correct?

Why are you using a gray card to set exposure for video?

Grey cards have their uses, to be sure, but aren't commonly used in video.

But to answer the question, if the card is in the same light as the subject, it can be close to the camera and properly reflect exposure values of the distant subject.

The more common exposure tools:
Waveform display, if offered by the camera.
Histogram, same.
Zebras at 100% for whites, or 70-75-80% (depending) for caucasian facial highlights.

Why a gray card? It may allow you to properly park an average exposure, but doesn't help you understand the exposure of highlights, which can get ugly real fast. All the commonly used tools give you highlight exposure values.

OTOH, a gray card can be used for white balance, and sometimes that middle exposure value is informative, but that's really a special application; controlling highlights is usually the thing.

A mid gray card probably more useful when shooting log, rather than when shooting traditional linear video. Although, it's not the most convenient method of setting exposures.

Hello!

I need some advice on this. When using a gray card to set exposure, suppose you're shooting at a distance. For example, suppose the subject is 50 feet from the camera. I assume the proper thing to do is to have an assistant hold the gray card where the subject would be (50 feet away) and then take the reading from that distance. Is that correct? I would assume standing close to the gray card would give an inaccurate reading...correct?

To answer your question, yes. You need to get the grey or white card under the same light as your subject. If the card is too small have the camera operator roll the focus out on the camera to try an fill the viewfinder with as much of color of the card as possible. If you look on Amazon, you can get different size fold up reflectors for a very reasonable price. The white side of the reflector is great for white balancing and many of them have silver and/or gold sides as well that are great for bounce lighting.