Embarrassing confession: I have never used a grey card. Please don't laugh.

Maris said:

The problem comes from the fact that grey cards are not perfect Lambertian reflectors. The"greyness" varies with the angle of the card versus the angle of the light versus the angle of the meter.

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The instructions with the card say to point it midway between the primary light source and the lens axis and meter from the camera position.

Amazing how easy things are when you RTFM (Read The Fine Manual).

- Leigh

Leigh B said:

I don't understand "... without metering the sky". :confused:

An incident light meter has an acceptance angle of 180°.

The only way you could exclude the sky from the measurement would be to point the meter at the ground.

Since the sky is a major source of illumination for the (outdoor) subject, excluding it from the measurement will give a significantly erroneous reading.

- Leigh

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My recommendations are relevant to reflectance metering only. How would one use an incident light meter to get spot readings of the brightest and the darkest areas?

How would one use a gray [grey] card with an incident meter? ==> Ill Elephant!

Some years back Calumet either sold or used as a promotion a plastic 8x10 gray card. It seemed like a clever idea and I cut mine into smaller more manageable pieces. I keep them in my camera bags just in case. On an early fall trip to Yellowstone one evening it was really freezing and early the next morning the windshield was frosted - it came in very handy as an ice scraper. (as well as the original intention with my spot meter - measure twice, expose once)

http://www.jeffreyglasser.com/

Holly said:

I'm so ashamed not to have more knowledge on this, I've only ever understood the use of grey cards in theory and not ever actually put one to use in my work.

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I've been shooting for years and I still don't know what gray cards are used for

IloveTLRs said:

I've been shooting for years and I still don't know what gray cards are used for

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The gray cards are used to match the tone of the sky on any typical day in Rocherster New York.

A friend had a ball cap, it was gray and instead of a ball team or other logo it said 18% on the front of it. We used to meter her head with it all the time. Wish I had a hat like that.
Anyone know where you can get an 18% gray card ball cap?

Does the ball cap really have to be gray or just 18% reflective. Maybe going to a sporting goods store with a light meter and gray card you can find one or one that is off by one stop and just reprogram the meter to compensate.

daleeman said:

A friend had a ball cap, it was gray and instead of a ball team or other logo it said 18% on the front of it. We used to meter her head with it all the time. Wish I had a hat like that.
Anyone know where you can get an 18% gray card ball cap?

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The George Eastman House in Rochester New York.

Rochester New York is the home of the 18% Gray sky.

Grey cards are the cheapest way to turn the foul device known as your in-camera meter into an excellent light meter. Place the gray card just like you would place the dome on an incident light meter, read the card, and then open up a half stop from what the meter says, and you are good.

michaelbsc said:

Let me make a suggestion before we really derail into insanity.

A gray card is a tool, nothing more and nothing less. It is not a magic wand.

If you have a particular problem with your work, then look for a solution to that problem. And *IF* the solution looks like it might be a gray card, then by all means get a gray card and start learning to use it.

But do not get a solution and then start looking for a problem in your work to solve with that solution.

That isn't to say that a gray card may not be just the thing you need. But you haven't said why you think you need a gray card, and now all these old guys like me are making jokes about it.

But again, don't fall in the trap of seizing a solution then trying to find a problem to fit it. First try to identify what area you need/want to improve, then look for the tool to do that. And if coming to understand and utilize a gray card for critical exposure control is part of that solution, then jump all over the gray card.

But a gray card is not a magic wand. Don't dismiss it, but don't put too much value in it either.

MB

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Hmm well it's a relief to know the 'old guys' haven't put much effort into grey cards over the years either from the sounds of it! I really thought I would be shamed and pointed at like a loser confessing that I don't have one

But anyway, I think I need to use a grey card for a kind of ball of yarn reason: when I shoot on 4x5 film, I always seem to screw up my exposures, and now that I will be basically forced to print negs digitally (graduated from Honours, no more free equipment access) I want to make sure I am exposing better, and able to use the grey card as a device for colour balancing in Photoshop once I've scanned.
So I guess I am wanting to be more controlled with my precious exposures and make sure the colours are able to be balanced correctly after scanning, and I figure if I start getting to know grey cards better, I can improve on both those levels?

@Holly. Bet you never expected to stir up this hornet's nest did you?

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Heh, no I didn't! It's fantastic!

Holly said:

But anyway, I think I need to use a grey card for a kind of ball of yarn reason: when I shoot on 4x5 film, I always seem to screw up my exposures, and now that I will be basically forced to print negs digitally (graduated from Honours, no more free equipment access) I want to make sure I am exposing better, and able to use the grey card as a device for colour balancing in Photoshop once I've scanned.
So I guess I am wanting to be more controlled with my precious exposures and make sure the colours are able to be balanced correctly after scanning, and I figure if I start getting to know grey cards better, I can improve on both those levels?

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If you're going that route, you might want to consider one of these:
http://xritephoto.com/ph_product_overview.aspx?ID=1257
which works with both film and in the digital domain with Photoshop, which we don't discuss here. dpug.org is the equivalent venue for those discussions.

Lee

Holly said:

when I shoot on 4x5 film, I always seem to screw up my exposures...

and now that I will be basically forced to print negs digitally (graduated from Honours, no more free equipment access) I want to make sure I am exposing better...

[need] a device for colour balancing in Photoshop once I've scanned.


I am wanting to be more controlled with my ... exposures and make sure the colours are able to be balanced correctly after scanning...

[Michael's editorialized paraphrase] Is a gray card and it's use a good place to start?

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Well, first, I'm not much of a color guy, so take everything from me with a grain of salt.

As I noted early on, now we have defined the "problem" you want to solve.

First, you need to understand several things. Those are (1) color temperature of light sources, (2)color balances of film stocks, and (3)filters to convert light sources from one temperature reference to another. It isn't magic, but it isn't trivial. And there are a lot of great older books floating around on the subject. I would also bet that there are a lot of good internet resources, too. Maybe someone can point them out.

As far as scanning is concerned, Lee is right, DPUG is a better resource. And there are some other good groups dedicated specifically to scanning as well.

But you are correct that your first problem to solve is getting the exposure correct on the film. And that problem is solved by understanding your (1) light source, (2) film balance, and (3) filter selection if the light and film don't match.

For that part I suggest that you first search the archives for stuff on the subjects (which I personally always find frustrating as hell), then after you've confused the daylights out of yourself (or maybe the tungsten lights) go to the Color: Film, Paper, and Chemistry forums and start asking a few questions about how Tungsten vs Daylight film react to various light sources.

As for the gray card, I suspect that you'll eventually end up using both a gray card and something like a McBeth color checker if you are doing very critical work.

I would use a gray card, but I'm color blind!

Jeff