using grey card

[Alpha]

but doesn't colour change under different lighting conditions.

You're thinking color target.

X-Rite Original ColorChecker Card MSCCC - B&H Photo Video

 

[KmH]

The beauty of the gray card is that regardless of what colors are lurking around the world, you can trust that your card will stay the same color within its life span.

Boy, don't we wish? The statement is true for most high quality greycards like a WhiBal card www.rawworkflow.com or an X-RITE ColorChecker Passport www.xrite.com.

It won't hold true for many of the cheap gray cards out there.

 

[shmne]

I've only recently gotten a balance card. Grey one side, White the other.

Using the grey side, I understand it should be positioned at / near the subject. Would it be best to shoot a full frame of the card or back off to the framed composition?

What conditons do you choose to meter the grey side or the white? Why?

Cheers

From what I've seen some people like to color balance in camera with white and in post with gray. I only use the gray side, though both can be used. I also prefer using models that have black so that when I apply curves to color correct I can make it three quick clicks.

 

[tom beard]

Thanks Mathews, I just got an 18% gray card, and they come in very handy for indoor mixed light sources such as mixed halogen,fluorescent, incandescent etc. I'm pretty sure it's for setting white balance (color temperature of light) and the colors themselves are irrelevant. My question is, is that you can also set white balance using a white card. What's the difference? Since I'm a Noob, I'll leave it to the members to correct me PLEASE. Tom Beard

 

[Flash Harry]

colors all reflect different amounts of light, can you see colour in a dark room, its all about reflectance, pure white reflects 100%, pure black reflects zero, there's a scale for reflectance in some photo book I had at college but cant remember which one, this is why in mono/BW photography colours will be defined as different shades of grey, greyscale, ring any bells. H

 

[Boomn4x4]

colors all reflect different amounts of light, can you see colour in a dark room, its all about reflectance, pure white reflects 100%, pure black reflects zero, there's a scale for reflectance in some photo book I had at college but cant remember which one, this is why in mono/BW photography colours will be defined as different shades of grey, greyscale, ring any bells. H

Here's a color graph. Anything at the top reflects 100% of light (white) anything at the bottom reflects 0% of light (black) Each shade of color has a reflectance, and any shade that is 18% of the way down from the top, will reflect 18% of the light that strikes it. They aren't reflecting the same frequency of light waves, but they are reflecting the same volume of light waves. And volume of light is what is important to exposure.

Or as a cutout.... anything in this color strip is reflecting 18%(ish)

Any color in that cut out, yellow, green, blue, gray could be used as a metering card as they are all reflecting the same volume of light. If you need proof, take that strip of color into photoshop and desaturate it... effectivly leaving only reflectivity left... the whole strip will be the same shade of gray

 

[Helen B]

Er, I think that you have got that upside-down: an 18% card reflects only 18% of the light hitting it. What you are showing is much lighter - 18% black at a wild guess (when black = 100% black). 18% grey is 18% up from black on a linear scale (when 'black' = 0% reflectance), and roughly 50% up on a luminance scale (which represents human perception).

You do need to be careful when using coloured targets for metering because there may be a mismatch between the spectral response of the meter and the spectral response of the recording medium. That is the advantage of using an incident metering method (that is effectively what grey, or white, card metering is) - it is relatively unaffected by mismatches in spectral response.

Best,
Helen

 

[supraman215]

I just looked up use grey card and found this.

Grey Card Instructions

Don't remember if it was posted already.

 

[Boomn4x4]

Er, I think that you have got that upside-down: an 18% card reflects only 18% of the light hitting it. What you are showing is much lighter - 18% black at a wild guess.

Yes, that is correct. Thank you for the correction.

I'm not suggesting that you SHOULD use colord objects, my intent is simply going back to the OPs question about when to use a gray card and how color is not necessarily relavant to metering.