The Grey Card

     Exposure is the scariest part of using a camera. You only get one chance per shot, and unless you are using a Polaroid or a DigiCam you will not know if you muffed it until at least an hour after pressing the shutter. Even with those two "instant" systems you will still not be able to go back in time for a second chance. So how can you be sure every exposure will be correct? How can you know for sure that you have each and every shot perfect? To be honest, you can’t. Every exposure is a guess. Let me repeat that with a little emphasis:

EVERY EXPOSURE IS A GUESS.

     You can guess the exposure by yourself, or you can have a friend do the guessing, or you can let the camera guess, or a hand held light meter guess, or the nearest ouigi board, tarot deck, crystal ball, chicken bones, or runes. It’s all a guess.

     Some methods and some guessers are more accurate than others - I rarely carry chicken bones these days. The crystal ball is a bit heavy and delicate for a walk in the woods too. I alternate between letting the camera do the guessing, and doing it with a little help from the camera and a singularly handy device - the Grey Card.

     At ten to fifteen dollars a pair, grey cards are probably the cheapest camera accessory you can buy. Yet few people bother with them, as they are a bit bulky and tend to slow down the shooting. I recommend a grey card as the first accessory for every student, and then proceed to show them how to get along without it. It’s kinda Zen like.

Using Your Grey Card

     When I first wrote an article on the grey card, I left out the basics, assuming everyone would have access to a good explanation either in a book, on a website, or packaged with the card itself. That was a mistake on my part. It turns out there are few good explanations available to most people, most of the time, in most places. So I’m including the basics this time around. If you already know how to use a grey card, please skip right to "The Grey Card Walk."

     The meter in your camera can be very simple or very sophisticated. It can be a simple center weighted, simple partial, simple spot, not so simple multi-spot, really un-simple matrix or full blown, evaluated, levitated, oxygenated, poly-unsaturated, zoned, honed, and be-moaned, 16 point by 35 spot, tri-weighted calibrated RGB, CMYK, SXY LSMFT with hemi heads and demi monde super meter. For the rest of this lesson I will assume you have a simple center weighted meter - and are using it.

     I am also assuming you have your camera in manual exposure mode, and have turned off any exposure compensation. Why don’t you check these details while I light up my pipe. Auto-mation is a wonderful thing, but it can spoil the heck out of a photography lesson.

     With your camera reduced to manual exposure lets take a picture of me standing on Franklin Street, facing the afternoon sun. I’m wearing a black sweater and standing in front of a big white Chapel Hill Transit bus. Move up close to me, so my face fills your viewfinder. Not bad looking for an old codger, eh?

     Now adjust your camera until the meter tells you the exposure is correct. Without changing the camera setting move the point of focus down to the black sweater. The meter isn’t so happy with the exposure any more, is it? Take a note of your first reading and then re-set the camera until it reads correct for the black sweater. Now move until the white bus fills the frame. The meter just got un-happy again didn’t it? Three different objects, three different readings - which one are you to believe?

     None of the above.

     Hand me the Grey Card. I’ll hold it up next to my face while you take a reading from it. Of the four readings you’ve taken, this is the one most likely to be correct.

     Meters can be very sophisticated but they don’t have a single spark of intelligence. They are merely devices that measure the light that falls upon their sensors. They are calibrated to read off a subject of average reflectance - which is exactly what a grey card is - a subject of average reflectance. Yes, there are smarter meters, but you turned yours off at the beginning of this lesson.

     Can you believe the reading you get off the grey card? Unless you have reason to dis-trust your camera meter you most certainly can - most of the time. In general it will usually guess close enough. You can try this out by stepping back until you have my face, my sweater, and some of the bus all in the frame. You will probably get a reading fairly close to the one you got from the grey card, as now the black, white and pinky/tan objects in the frame added together come close to averaging out at the same level as the grey card. Average?

     Your meter is called an averaging meter. It measures the light from all the areas it sees, and gives an average reading. Since most front lit scenes (remember I’m facing the sun and you are facing me) will end up with the dark and light shades averaging out to the same reading you would get from a grey card. In actuality the grey card is not really necessary for these average conditions.

     What if I change from a black sweater to a white shirt though? Now we have a problem. There is nothing in our picture with a dark value. We cannot find the average reflectance because everything in the frame is of above average reflectance. If we believe the meter we will surely under-expose the picture. The grey card will save out bacon, by giving us an "average" for our metering.

     No matter how much light falls upon it, the grey card remains the average. Being half way between white and black it IS average colour. If we want to take a picture of the bus only, and know our meter will be fooled by the great expanse of white, all we have to do is hold up the grey card, in the same light as the bus, and take our reading from it. The same is true if we wish to photograph the sweater alone, or my face, or anything else. All we have to do, is put that card in the same light, take our reading and Bob’s your uncle.

     What do we do if we’re in a hurry, and can’t take the time to meter off a grey card, or the card is back in the car, or lost? We can’t always have a grey card handy, and we frequently have no time to use it. It’s time for a little walk.

The Grey Card Walk

     This little trip should be one of discovery for both of us. You carry the camera and therefore the light meter, while I carry the grey card. I’m not really necessary, but I do come in handy. When I’m not around to walk with you, do it alone. I’m really only a movable stand.

     We’ll start on West Franklin Street and work our way east. It’s mid afternoon, and as usual, a bright sunny day in downtown Chapel Hill. We know that the light meter wants to see something with the same reflectance as that grey card, but nothing out here is that particular shade of grey… Or is it?

     Lets try the street surface. The bus finally left so we probably won’t get run over in the bus stop. I’ll lay the grey card down in a sunny patch, and you compare the reading it gives you to the reading you get from the concrete itself. What is the difference? Is the street lighter or darker than the card? By how much? If you didn’t have the grey card, how would you go about getting the correct meter reading using the street surface? I’m not going to give you the answer. I just hold the card. Take your time and compare. You know that lighter subjects reflect more light and will under-expose, while darker subjects reflect less light and over-expose. Which is this piece of street going to do?

     Okay, now lets look for other greys. The sidewalk is lighter than the road. I’ll set the card down and you can compare it again. What’s the difference now? How would you meter if instead of an 18% grey card you had a Sidewalk Grey card? How does the sidewalk compare with the street?

     All very well and good you say, but not everything in the world is grey. The defunct burrito restaurant is dark brick colour, and the empty Hardees is light tan. There’s a brown phone pole, a yellow take out joint, white, blue, green, and every other colour imaginable - except for the street and the sidewalk, there is nothing grey in the entire town. How do we meter them?

     Actually, it’s quite simple. Your light meter does not care about surface colour. It cares about reflectance. Everything reflects a certain amount of light, but the colour of that light is quite unimportant. Take one reading off the bricks and another off the grey card as I hold it up to the side of the empty burrito place. How do the readings differ? Now lets try Hams Bar. The building is off white, but the plate glass windows are quite dark. Try each, and compare to the grey card. Now try metering an area that takes in some of the white wall and some of the dark glass. Compare.

     As we work our way up the hill we will stop at every new colour, new kind of object. We don’t have to limit ourselves to things that can’t move. How about the delivery van, the cars parked at the gas station. There are people about. Some of them will not mind holding the card while we do our comparisons. Brown purse, blue blazer, white tee, green dress. What about the doggie? Nice doggie. Does the doggie bite? Perhaps we don’t need to meter the doggie.

     At the corner of Columbia Street. There is another big white bus, and a driver in dark blue. Across the street is the row of newspaper machines, in orange, green Carolina blue, black, and white. Meter them all. We’re on a roll.

     We can cross Franklin here too and get cooler on the shady side of the street. How about the sidewalk here? Is it darker than the one we metered in the sun? Obviously it is, but there is another question to ask ourselves. Is it darker in relation to the grey card, than the sidewalk in the sun? I give no answers. I just hold the card. You tell me.

     By the time we get to the Coffee shop you have a pretty good idea of how to use a grey card for proper exposures, and how to get those exposures from substitutes. Now would be a good time to look for a substitute that’s always close to hand - Very close to hand.

     In fact, it is your hand. Not the back, though, meter your palm. How does it compare to the grey card? Is this a neat trick or what? We metered the palm because it will not tan. Your palms will be the same reflectance summer and winter. The back of your hand will not.

     We’ve arrived at the Coffee Shop. I’m hot and getting a little cranky so I’m going in for an iced tea and a little Vivaldi - it’s usually Vivaldi at the coffee shop around this time. You job is to try out a few more grey card substitutes. How about the trees in the church yard, the wall, the skateboards, students, whatever?

Your Next Assignment

     Tomorrow you can head out into the woods with the card, or take it to a monster truck rally if you like. For a while the grey card should be your constant companion. Use it on anything you can get to hold still. Try it at all times of day. Does the sidewalk have the same relationship to the grey card at sunset that it had at noon?

     Even after you know every single thing that can substitute for the card, keep one in your car. It doesn’t take up much room, and you never know when you’ll find a new place to try it. How about that dim little bar with the pool table? You can never know too much when it comes to metering.

P.S.

You did remember to meter your camera bag , didn’t you?