Gray Cards

March 5th, 2012 § 0 comments

20120303-235205.jpgGray cards are an important tool in a photographers arsenal. They serve two purposes:

1. Exposure
2. White Balance

Ansel Adams helped develop the Zone System that consists of 10 stops of light from black to white. (You can google the Zone System for more information) Zone 5 is considered middle gray or 18% gray. Since cameras (as of yet) can only capture half the zones in an image, the photographer has to choose which zones that would give the best exposure.

Cameras and Light Meters (reflective) are programmed to meter a scene at 18% Gray, but not every scene or object has a gray to meter. The camera or light meter will try to give an approximate reading, but it can often be incorrect. The best choice in this scenario is to spot meter a gray card that is reflecting the light back at the camera or light meter.

20120304-001414.jpgHow do you use it? Let us use the image above as an example. I set a bowl against a dark background and had it sit under a 100 watt shop light using my iPhone camera. As you can see, my iPhone auto exposed the scene and blew out the bowl since the scene was mostly dark. The meters will lighten a dark scene and darken a light scene.

20120304-002221.jpgStart by placing the card in front of your subject. The light reflecting off the card will give a true reading of middle gray, and the photographer can choose the exposure needed.

20120304-002824.jpgI selected the X on the card, with my iPhone, because the focus requires contrasting elements to lock on to, and it was also one of the lightest parts of the card. A slr camera and light meter is different. The spot meter is aimed at the gray for a reading, and the photographer can focus on the X or remove the card and focus on the object.

20120304-003727.jpgRemove the card, and start taking pictures. You may need to adjust the card for better readings, but for the most part, your exposure should be correct.

As for the white balance, the gray card has also changed the color temperature to make the colors true. Tungsten, fluorescent, LED, sun, moon, and other types of light have their own color temperatures that can change the look of an image. White balance is different with each camera, so refer to your owners manual for more information.

Give the gray card a try, and you will be amazed at the differences that are made to you’re images.

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