Grey Cards

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Philx1979

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How many people use grey cards?

Am i right in thinking they can be used for White Balance setting AND exposure control or just the WB?

I know you can take a picture of the grey card in the 1st picture of the scene shoot and then use a dropper in photoshop to correct WB if you shoot in raw, would this change exposure afterwards or just the WB?
 
I think how useful grey cards are depends on what/where you're shooting.

If you're in a studio you can set your props/lighting up then shoot a grey card to get the correct settings but if you're shooting say a rugby match where the sun's in/out, some of the pitch is in shade and the background varies between trees, spectators etc a gey card isn't that beneficial to set exposure or WB.

If you shoot in RAW then it's very easy to correct WB in PP. You can shoot a grey card and set custom WB on the camera, however as above, that's only good if conditions stay exactly the same during the time you're shooting.
 
Philx1979 said:
Am i right in thinking they can be used for White Balance setting AND exposure control or just the WB?
Click to expand...
Yes, you're right. Take a shot of the grey card filling the frame and that will tell you what exposure you need - so long as the light doesn't change, of course.
Philx1979 said:
I know you can take a picture of the grey card in the 1st picture of the scene shoot and then use a dropper in photoshop to correct WB if you shoot in raw, would this change exposure afterwards or just the WB?
Click to expand...
It wouldn't affect the exposure.
 
Does anyone know what the exact procedure is in both PP and LR please? I would be looking at doing this for 50 pictures so would need to know how to include all 50 pictures with the same command? Thanks
 
You can use it for both - Basically for exposure you have to align the card at a 3rd of the horizontal angle to the main light (e.g the sun) and a third of the vertical angle as well and then meter off the card, preferably using spot metering and then add on 1/2 a stop for subjects of normal reflectance.

Basically it gives you an incident light metering rather than a reflective reading like all camera meters do so you'll get a much more accurate exposure if your taking pictures of a snow capped mountain for instance as that would reflect back more light and fool the camera into underexposure normally. It works on how much light is actually there rather than how much is reflected.

A Kodak R-27 grey card set of 2 10"x8" and 1 4"x5" grey cards comes with a pretty comprehensive but simple list of instruction on how to use them for metering exposure.
 
Just make sure that the grey card is both neutral grey, and 18%.

Some sold purely for white balance are not 18%, and some that are sold just for exposure are not neutral!
 
Are the insides of certain camera bags supposed to be 18% grey or is that a load of old hogwash I read somewhere Richard?
 
fracster said:
Are the insides of certain camera bags supposed to be 18% grey or is that a load of old hogwash I read somewhere Richard?
Click to expand...

Internet myth, though some are close. I have three Lowepros that are all close, but none spot on, mainly too light. Handy as a constant reference, but not for strict accuracy. I've got a Spudz lens cloth that's pretty good ;)

Whether 18% grey is 'correct' for exposure is another question altogether ;)
 
Thought as much, thanks for the clarification Richard.
 
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