Sunday, 25 October 2009

Using a Grey Card for Photography

Interesting enough lately I have been seeing more than one discussion on the use of a grey card for photography and if it makes a difference. The topics have been varied from photographers saying they are a waste of money to others who are misleading some on what they are actually used for and  how to use them correctly.
Recently on our Bluedog-Kingfisher Bay Fraser Island Photography Tour we revisited the use of the grey card and Judy has kindly sent in the images below that she took which demonstrates how it works perfectly. Neither of these images has been touched in Photoshop or another editing program.
What we need to understand when wanting correctly exposed images is how light works and how our cameras read light.
Reflected Light:
This is the light our cameras light meter reads. It measures the light reflecting off the subject. A dark object reflect less light than a bright subject and therefore this can trick our cameras light meter.
Incident Light:
Is the light falling on our subject. This was the light our hand held meters usually read. And therefore were not influenced by the subject's reflectance. Many hand held meters can read both incident and reflected light. Incident light meters can be identified by their white translucent dome over the light sensor.
In summing up, the grey card is one of the most useful, inexpensive tools you can have in your kit and knowing how light is read by your camera and how you can adjust your exposure means you are in control. You are the one that can get exposure right in camera – your whites white and your blacks black - which means, you are the photographer!
Tips for Using a Grey Card:
Always position the card parallel to the front surface of your lens.
Don’t tip the card towards the light as it be reflecting too much light and not give an accurate reading.
Don’t tip the card down – then there’s less light, the opposite of above.
Be careful using other grey objects just because they look ‘close enough’. Their reflectance may trick your cameras meter.

This image was taken using what the cameras meter said was the correct reading.

This image was taken using after using a grey
card to set the cameras meter reading.

Images courtesy of Judy Watts

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