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class="Paragraph" Meters & 18% Grey Card Myth

Published : 5th March 2004


Walter Graff writes:

http://www.bythom.com/graycards.htm


Interesting web page Walter. But as he says, if you calibrate it doesn't matter what percentage gray card you use. Just like the Zone System, I base my calibrations on dmin of the printstock. I adjust to get the maximum (visual) black that is possible before reciprocity sets in.

Steven Poster ASC



>Interesting web page Walter

But as he says, if you calibrate it doesn't matter what percentage gray Card you use.

I thought it was interesting too, hence why I shared it. But like everything else in life we find that references are never written in stone and there is room for error. Or as the article states =8Cwhatever method of setting exposure works for you, use it.

I just wanted folks to see that 18% grey technically is a figment of the imagination, or of any one manufacturer and not another, or as the article states, someone made it up, but who?

>Just like the Zone System, I base my calibrations on dmin of the >printstock.

I adjust to get the maximum (visual) black that is possible before reciprocity sets in.

And you'd be more accurate there than a person assuming 18% was accurate.

Walter Graff
Producer, Director, Creative Director, Cinematographer
HellGate Pictures, Inc.
BlueSky, LLC
www.film-and-video.com



Walter Graff wrote :

> http://www.bythom.com/graycards.htm

Yah, interesting article Walter. My Canon D60 does the same thing, shooting a grey card using the built-in metering and using a separate exposure from my Sekonic produces about a 1/2 to 1/3 stop underexposure, but I thought it was the camera's firmware that was automatically underexposing the image in order to prevent highlight burnouts. The reason behind this thinking was that the earlier firmware on my Canon (1.0.2) didn't produce this underexposure (it shot 18% grey at the middle of the histogram), but when I upgraded to 1.0.4, then I had to deal with this "slight" but rather annoying underexposure problem. It's nice to know I guess that it's actually a mis-calibration in the metering and not some engineers over at Canon thinking I need a bit more overexposure latitude, so they're dialling it in for me automatically.

Jason Rodriguez
Post Production Artist
Virginia Beach, VA



Jason Rodriguez wrote:

>but I thought it was the camera's firmware that was automatically >underexposing the image in order to prevent highlight burnouts.

A digital camera should have a setting that automatically sets the exposure (or indicates it, in manual mode) so that no pixels are blown out -- so that you retain the entire dynamic range for post-shoot correction. Of course, you could ignore that if you want to blow things out, obviously, especially if the sensor's dynamic range isn't as wide as that of your subject.

Jeff Kreines