Mwendell

Would someone please help me understand how to properly use a Gray Card to set the correct exposure, instead of a lightmetter?

For example; your shooting a person standing up with a very bright top half background and a very dark bottom half of the frame. You want the person to be exposed correctly without blowing out the top and bottom halves.

If you can, give me some other scenarios where a gray card would be especially helpfull.

PS. I think I should have started out by asking everyone to explain how a Gray card works.

Thanks to those of you who take the time to reply with any help.
Mwendell

ShakyShutter Loc: Arizona

Technically speaking the gray card is for use WITH a light meter.
The light meter may be inside your camera or handheld.
The gray card is used mainly to provide a standardized reference that equates to the middle step of a 10 step gray scale.

How the average user should use it... now that is the question.

LarryD Loc: Mojave Desert

Gray cards are most often going to be used for getting correct color or setting a custom white balance.. not usually for getting a correct exposure with a wide dynamic range scene..

When you have a scene with a bright upper and dark lower, you meter on the part you want to be correctly exposed, such as meter on the sky if you want blue and puffy, well defined clouds, and let the foreground go dark.

You can also meter both or several areas and use the average setting, but that will not guarantee non-blown highlights..

Landscape photographers frequently use a graduated neutral density filter that is a couple of stops darker at the top fading to clear at the bottom..

steve40 Loc: Asheville/Canton, NC, USA

Gray cards were used with film, to determine an exposure under difficult lighting conditions. But today are mainly used for neural white balance, with problematic lighting. But under the conditions that a very broad dynamic range exists; usually its easier to expose for the subject, and let the rest fall where it may. Of course there are graduated neutral density filters, and bracketed exposure HDR, that will take care of such situations but are not always convenient.

Sometimes the best thing is to try to find better light conditions, or just simply pass the shot by.

beacher Loc: Butler, PA

You are mixing apples and oranges. Exposure is all about how much light enters the camera. White Balance - WB - is about how the camera interprets that light. You set the card next to or as near to the subject you're shooting, and take a test shot making sure you have that little bullseye in your viewfinder centered on that card. You then use this test picture as the reference for your custom white balance setting on your camera (RTFM for this). This lets the camera know how much light is reflected back to it, thus allowing it to adjust itself accordingly. You've used the settings cloudy, partial shade, bright sun, office lighting, indoor lighting, etc? Well, this is just a more accurate setting for the same parameter-- a here and now, as opposed to an average, setting. Hope this clears it up for you...

Dun1 Loc: Atlanta, GA

A grey card is used to set or correct the white balance. The light metering is set based on your settings. In most instances if you select AWB (Auto White Balance) you can be pretty well within limits. You can also buy tools or extras to correct the white or color balance on the camera, Expo Disc, Color Rite etc.
http://www.expoimaging.com/
http://www.petergregg.com/

JKF159 Loc: Arkansas

I'm not really familiar with using a gray card for white balance but I know that gray cards were in use long before there was any such thing as white balance.
The gray card is 18% gray. A reflective type light meter like the one in your camera is set to assume the subject is 18% gray. Everything is not 18% gray. If a subject is white the meter, in an effort to make it 18% gray, will underexpose by a couple of stops. If its black then overexposure will be the result. You can use the card to meter off of to give the light meter a standard that it was set for. The card must be in the same light as the subject.
The card will not keep you from blowing out highlights or having shadows that are too dark, it only can tell you what the exposure of the shadows and highlights should be. If this exceeds the exposure range of the camera then one or the other will be too light or too dark.
The reason 18% gray is used for meters is that a clear blue sky viewed at a 90 degree angle from the sun is 18%. Also green foliage in sunlight is 18% gray. This could represent a large part of a landscape photo.
TIP: Use the palm of your hand as a gray card. Meter your hand in the same light as your subject then open up one f stop. Your hand is more portable than a card and you always have it with you. It works very well.

snowbear

Since grey cards came from the film era, they were originally used for setting the exposure; you don't set white balance with film. If you are outside, a quick substitute for a grey card can be green grass, which is fairly neutral.

Most cameras have a feature for adjusting white balance by photographing a plain white surface. You could use a grey card for tuning white balance in post-processing, but you could as easily use a white object.

Edit: JFK159 beat me to it :)

beacher Loc: Butler, PA

meters are set for 12% reflectance not 18%. Gray cards are 50% black and 50% white, middle of the pack. Their reflectance is a flat 18% . Other colors -- like green grass -- can be blown out depending on the lighting. Or depending on other chemicals or minerals the grass may be exposed to. The whole idea of gray cards is to balance neutral colors. In jpg or tiff, for example. In raw really doesn't matter much, because you can adjust post process. WB doesn't really come into play until you process the raw file. There are plenty of references for this if ya just google. These forums are for short answers, not blog length dissertations. You can't really cover all the nuances of some question/answer situations. Not trying to be rude, apologize if it seems that way. Nature of these forums, stifles the emotional aspect of answers :lol: , the nuances of speech.

GENorkus Loc: Washington Twp, Michigan

I really wouldn't worry about using a gary card unless your unhappy with the final print and have to have "gray". Generally todays cameras are pretty close on auto as long as you don't use really warm lighting like tungston etc.

Should you want to use a gray card, as a simple suggestion go to a store that sells paint and pick up something that is close. (I've found several close grays with the name including "smoke".

As another close "gray" you can use an old gray colored sweat shirt or a piece of a gray colored underground plastic pipe.

Your editing program will get you close.

marmesto Loc: Hamburg, NY

I had completely forgotten about metering off the hand absent a gray card. Thanks for the reminder.

XJoeyX Loc: San Antonio, TX

What is neural white balance?? :lol: Sounds like you might need a medical degree to acheive this... Hehehehe

-Joey

ShakyShutter Loc: Arizona

PS. I think I should have started out by asking everyone to explain how a Gray card works.


Advise you seek learn'n about the gray card outside this forum you will simply become more confused by this discussion.

JKF159 Loc: Arkansas

Sorry for the lengthy post. I really thought I was being brief. I took your advice and googled gray card. Here is a couple of quotes from what I found.

1. "A major use of gray cards is to provide a standard reference object for exposure determination in photography."

2. "This topic deserves a discussion of its own, but for the purposes of this tutorial simply know that each camera has a default somewhere in the middle gray tones (~10-18% reflectance). "

I am aware that gray cards are used for white balancing, I just dont know much about it. All I was pointing out is that gray cards were used for accurately measuring exposure long before white balance was an issue.

Yes, different subjects like green grass can be blown out (overexposed), however if you metered off of a gray card that was setting in that grass then the grass would not be blown out. That is what the gray card is for.

The origonal question was how to use a card for exposure. Somebody else brought up white balance. There are many other details that could be addressed concerning this but to keep it brief I'll stop here.

Mwendell

Beacher, you don't need to apologize and I don't think your rude. You're just flat wrong. JKF159 used 16 lines to answer my question, which was 9 lines. You took 18 lines to answer, so who's the blogger now? After all the name of this particular forum is "Main Photographer DISCUSSION", and some discussions just happen to be a little longer than others. I really believe that JKF159's reply was good one and he gave us a good Tip or two. Your two combined Blogs, excuse me, that should be Replies, were rather smug as though you were out to prove to everyone that you know more about the subject than any one else. I consider your statement, "These forums are for short answers, not blog length dissertations." to be a slam on JKF159's reply. If you believe in what you said in your second reply, you could have skipped everything in both your replies except for one sentence you wrote, which I quote "There are plenty of references for this if ya just Google".

I think we both have too much time on our hands, when we should be out shooting. When you have some time you should apply for the position of Forum Monitor, you would be good at it.
Kind regards,
Mwendell