18% Gray Card

CS
Posted By
Chuck_Snyder
Jun 8, 2004
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338
Replies
8
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Closed
I’ve been trying to understand the concept of the "18% gray" card which is used as a benchmark in film photography and enlarging. What makes it 18%? It’s certainly not 82% black; it seems very close to middle gray (50% K), at least on my poorly calibrated monitor. Is it appropriate to use an 18% gray card as the midpoint/exposure point for digital photos? I’m not getting this one…

Chuck
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JF
Jodi_Frye
Jun 8, 2004
Chuck, here’s a real mind twister 🙂

<http://www.cameraguild.com/technology/gray_card.htm>
EW
Ed_Wurster
Jun 8, 2004
Chuck wrote:
I’ve been trying to understand the concept of the "18% gray" card which is
used as a benchmark in film photography and enlarging. What makes it 18%? It’s certainly not 82% black; it seems very close to middle gray (50% K), at least on my poorly calibrated monitor. Is it appropriate to use an 18% gray card as the midpoint/exposure point for digital photos? I’m not getting this one…

The grey card is held at a 45 deg. angle to the light source, and the photographer takes an incident meter reading of light reflected off the card. The grey card approximates an average skin tone. I think the card is supposed to reflect 18% of the light that hits it.

Here’s a recent rec.photo.digital thread about it: http://tinyurl.com/ysz5n

Ed
CS
Cliff_Skidmore
Jun 8, 2004
18% or 12% see:

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

another link:

<http://www.garageglamour.com/tips/graycard.php>
GD
Grant_Dixon
Jun 8, 2004
Chuck

There are not proper exposures just appropriate exposures.

A light meter whether in a camera or hand held sees the world as an 18% grey card. It you are shooting a coal bin or a polar bear in the snow the light meter doesn’t see the black of the coal bin or the white of the polar bear but an 18% grey. So if you trip the shutter in one case the image will be under exposed and the other over exposed. So in comes the 18% grey card, think of it as an incident meter. By metering of the grey card you will get the true measure of the light. You may then adjust up or down to get more or less detain in you image. For 95% of exposures if you meter off a grey card and also off the image (reflected) then the appropriate exposure is the value that is midway between these two methods.

In my Photograph of the day the Secret Garden and Dame’s Rocket where metered with an incident light meter that would be the same as using a 18% grey card.

Grant
BG
Byron Gale
Jun 8, 2004
….and everyone scoffed at my "tone balls" post!!

Dick Smith "Tone Balls" 3/25/04 3:25pm </cgi-bin/webx?13/0>
LK
Leen_Koper
Jun 8, 2004
If you buy the Kodak -which is extremely expensive for a piece of cardboard- neutral grey card, use it just only for determining the exposure and NEVER to balance the grey tones of the image. The colour isn’t neutral grey at all.

Leen
CS
Chuck_Snyder
Jun 8, 2004
Thanks, all. It’s starting to sink in….until I forget it again….

🙂
JF
Jodi_Frye
Jun 9, 2004
That sounds too familiar

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