18% Grey Card & camera metering system


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thomas990

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#1
i've just read this article by thom hogan:
http://www.bythom.com/graycards.htm

what thom hogan mentioned was about the 12% grey instead of 18% grey.. and in this case, nikon calibrate their camera metering system to 12% grey.

myself do not own a grey card but intend to do so.. but i have to make this clear before hand.

according to thom hogan, when we manually set exposure base on the 18% grey card, we have to open up 1/2 stop. so how does it correlate with the camera metering, for instance when i do not meter on a grey card but on the subject itself directly? do i need to compensate my exposure?

the fact is, i normally compensate my metering by -0.3. cos the original metering is a bit too bright for me. is this proper?

any kind soul pls advise, thanks!
 

#4
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according to thom hogan, when we manually set exposure base on the 18% grey card, we have to open up 1/2 stop. so how does it correlate with the camera metering, for instance when i do not meter on a grey card but on the subject itself directly? do i need to compensate my exposure?

the fact is, i normally compensate my metering by -0.3. cos the original metering is a bit too bright for me. is this proper?
What Thom Hogan is trying to say is that Nikon cameras meter using a 12% Grey ANSI standard rather than the 18%. So this would mean that the histogram would show a peak on the left of the center (is underexposed). This is based on spot or center weighted metering on an 18% Grey Card.

Only professional photographers who want to ensure a consistent exposure across many photographs in the same location would use a grey card as a metering reference.

For normal folks, there is no need to worry about that underexposure bias from Nikon.

Just apply your exposure adjustments accordingly. As little wolf mentioned, if the exposure is okay to you the photographer, than it is the correct exposure!
 

theRBK

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May 16, 2005
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#6
I have also found the metering system in my D200 to underexpose by ~1/2 a stop and have it permanently adjusted upwards 1/2 a stop... found it works for me and have been using it like that since I got the camera... YMMV
 

#7
I have also found the metering system in my D200 to underexpose by ~1/2 a stop and have it permanently adjusted upwards 1/2 a stop... found it works for me and have been using it like that since I got the camera... YMMV
The following article has all the mathematics worked out, for those who need the scientific proof.

http://www.richardhess.com/photo/18no.htm

Basically, what this gray card expert is trying to say is at the bottom of his article:-

"Using the 18% gray card as a metering reference will cause approximately 1/2 stop underexposure as the reflected light meter is assuming 12%. "

Thanks for confirming this!
 

thomas990

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#8
What Thom Hogan is trying to say is that Nikon cameras meter using a 12% Grey ANSI standard rather than the 18%. So this would mean that the histogram would show a peak on the left of the center (is underexposed). This is based on spot or center weighted metering on an 18% Grey Card.

Only professional photographers who want to ensure a consistent exposure across many photographs in the same location would use a grey card as a metering reference.

For normal folks, there is no need to worry about that underexposure bias from Nikon.

Just apply your exposure adjustments accordingly. As little wolf mentioned, if the exposure is okay to you the photographer, than it is the correct exposure!
thanks a lot. it's useful to me :)
 

thomas990

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Jan 28, 2007
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#9
I have also found the metering system in my D200 to underexpose by ~1/2 a stop and have it permanently adjusted upwards 1/2 a stop... found it works for me and have been using it like that since I got the camera... YMMV
hmmm i tuned it down by 0.3...
 

#10
hmmm i tuned it down by 0.3...
I've come across some internet articles stating that not all cameras (even the same models) are metered the same way.

By way of analogy, it's like using a rifle in a shooting range. Some rifles tend to shoot their bullets upwards or downwards or sideways, so the shooter has to make the corrective adjustments.

Maybe your camera is biased towards overexposure???
 

thomas990

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#11
I've come across some internet articles stating that not all cameras (even the same models) are metered the same way.

By way of analogy, it's like using a rifle in a shooting range. Some rifles tend to shoot their bullets upwards or downwards or sideways, so the shooter has to make the corrective adjustments.

Maybe your camera is biased towards overexposure???
sensible enough :)
so it's all down to individual camera liao.
 

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