grey card?


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catchlights

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#2
Use photoshop set RGB 128, 128, 128, that's 18% grey, you can make a 5R print with white point (255, 255, 255), black point (0, 0, 0) a 18% grey in the center.

Technically are perfect, but all the prints from the labs do have slight color cast.
 

Jul 17, 2005
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Clementi
#3
just to check, this grey card is used to set white balance right? so you place the cam in front of it and shoot? then load the profile into the camera?

can this also be used for exposure/metering?
 

catchlights

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#4
You can use the gray card to preset your white balance, fellow the instruction written in your camera manual.


Or you can shoot a gray card in a picture, when open the image in photo editing program, use the gray (mid tone) droplet to click on the gray card, it will set the correct color balance of the image.


You also use a gray card to do exposure metering, or to check exposure, it will show the peak right in the center of the histogram if the exposure is correct.


This is only a brief usage of gray card, please do a detail search on the use of gray card, because I’m not good in writing.
 

Splutter

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#5
I think the above method by catchlights is just an estimation. The actual reflectivity is also highly dependent on the matrial's surface. There's a reason why greycards cost like $18 and not $0.30. But for normal use, I guess that's the best we can do :)
 

catchlights

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#6
You can tilt the homemade graycard a little to avoid reflection, but this homemade graycard may have slight color shift, even a Kodak graycard also need to replace after a being using for a while.

graycard or expodisc is to help you get a neutral white balance, but this may not the white balance that the photographers are looking for, some prefer cooler tone or warmer tone for some scene or another.

Hope this help.
 

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