Can someone please tell me what a grey card is?

I've seen it in this forum a couple of times. But don't know what it is, what it's used for, and if it's essential?

Camera light meters 'look' at the scene you are pointing at and evaluate/average all the light. Then it adjusts the settings to try and make all that light equal an 18% gray tone... which is kind of 'average'. So a gray card that is aleady that tone can be shot which makes the camera meter/reading more accurate than if you were shooting a bride wearing white on a whote background. Because all that white would 'fool' the camera into thinking there is more light than there really is and cause an underexposure.

So if you shoot the gray card and note the settings, the next shots in the same light can be locked in by setting the camera on manual and dialing in those setttings and the exposure will be fine and not drift on you everytime a tone changes even when the light does not.

Also, if a gray card is truely neutral in color it can be used to set a custom white balance as well.

Ran_photography wrote in post #6087937
I've seen it in this forum a couple of times. But don't know what it is, what it's used for, and if it's essential?

Heh! Check out the Similar Threads links at the bottom of the page and you will be able to read more than you probably wish!

In a nutshell, a grey card can be used to set a scene exposure (since the camera "reads" an exposure target to be approximately "medium grey") and can be used as a Custom White Balance tool -- if the card is, in fact, neutral grey, then the camera can accurately translate that to "neutral white" for white balance.

Anyone over 50 has to carry a "Grey Card" for discounts on coffee.

stathunter wrote in post #6088005
Anyone over 50 has to carry a "Grey Card" for discounts on coffee.

Hey, now you're getting personal!

stathunter wrote in post #6088005
Anyone over 50 has to carry a "Grey Card" for discounts on coffee.

Unless, of course, you have a gray head (remaining hair plus beard).