Some of you might have noticed this picture in my Flickr pics about the light tent and wonderd what it was. Simply put it is a Gray Card and may just be the cheapest yet most useful tool a photographer can have.

So what is it and why should you have one. Well it’s a gray card I know that doesn’t sound like much but it is a special gray. It is middle gray or 18% gray. Now in order to explaine why this is imporant we will have to get techinal for a moment. All modern cameras use something call TTL (Through The Lens) metering. The metering sensor sees what the lens sees and based of that determans the corrent shutter speed and aperture settings for the correct exposure. What the sensor is realy tring to do is make it so that the majority of the picuter comes out middle (18%) gray this prevents the photo from being overexposed (too much light) or underexposed (too little light).

Now most of the time this work just fine but the problem is that the system is figuring out how much light is falling on the subject by measuring how much light is being reflected by the subject. It relay easy to see that problems are going to accrue if the subject is overly light or overly dark. Now one way to solve the problem is to buy a light meter, you place the meter near your subject and it tells you what to set you camera shutter speed or aperture to. The problem a light meter is that they are not cheap by any stretch, enter the gray card.

Compared to a meter a Gray card is dirt cheep I paid seven dollars for a 2 pack (plus four dollars for shipping). So here’s what you do. Set the gray card near where your subject is. Then using your camera fill most of the frame with the gray card. Let the TTL metering to take off the gray card, because the card is middle gray already the camera get a lot more accurate idea of how much light is really falling on the subject. Make a note of what the TTL metering reads then using the full manual setting on your camera set the shutter and aperture to that reading.

Here are a couple of examples.

The picture on the left was taken with TTL metering, because the subject is in front a very white background the camera gets fooled into thinking that there is a lot more light falling on the subject then there really is. So, things turn out overly dark, the white background turns out grayish and Saber turns dull and sickly looking. The picture on the right was taken using the readings from the gray card, the background is white as it should be and Saber’s health glow comes though. Now according to the TTL metering the picture on the right is over 2 stops overexposed but as we can see it is not so while TTL metering is good for about 80% of picture taking, it’s that 20% that can make a big difference.

Now using a Gray Card for metering is just on of many thing they can be used for and for under ten bucks it is something any photographer should have.

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