ACE Camera Photography Magazine

The Tool for Better Exposures
How to Use an 18% Gray Card
18% reflectance gray card One of the most
useful, inexpensive
tools a photographer
can own is a gray card
Many amateur photographers have never seen a gray card. Others have seen one but don't understand the significance behind gray cards or the many uses they have in photography.

The last twenty-five years of increasingly automated cameras has made it easier for everyone to take good pictures, the downside of auto-everything cameras is many photographers today don't fully grasp how the light meter in their camera works, or when they need to manually intervene to get a properly exposed photograph.

Some background
There are two categories of photo light meters:

Reflected light meters - the type of light meter found in every camera, it measures the light reflecting off the subject. There are also handheld reflected light meters to determine exposure settings for cameras which lack a built-in meter, and spot meters measure the light reflecting off a very small part of the scene. Because dark objects reflect less light than bright objects, a reflected light meter can be tricked by an unusual subject or background.

Incident light meters - a handheld light meter which measures the light falling on the subject. Incident meters are not influenced by the subject's reflectance. Many handheld meters can measure both reflected and incident light. Incident meters can be identified by a white translucent dome over the light sensor. A good quality incident light meter can cost a couple of hundred dollars or more.

Measuring the light
Both reflected and incident light meters are calibrated to measure the light in a scene and produce a medium gray tone, the same value which is represented by the gray card.

Designed Specifically
for Digital Photographers
Perfect-Pix color rendition and gray tone cards for digital photographers

Perfect-Pix Color Rendition
and Gray Tone Cards

Serious digital photographers have the added challenges of white balance control and color management when viewing and printing their images.

Designed by photographer, educator and Gicleť printmaker, Christopher Wade, the Perfect-Pix cards solve many exposure and color accuracy issues faced in digital picture taking.

To learn more about these useful digital camera tools, visit Perfect-Pix.

Many amateur photographers have never seen a gray card. Others have seen one but don't understand the significance behind gray cards or the many uses they have in photography.

The last twenty-five years of increasingly automated cameras has made it easier for everyone to take good pictures, the downside of auto-everything cameras is many photographers today don't fully grasp how the light meter in their camera works, or when they need to manually intervene to get a properly exposed photograph.

Some background
There are two categories of photo light meters:

Reflected light meters - the type of light meter found in every camera, it measures the light reflecting off the subject. There are also handheld reflected light meters to determine exposure settings for cameras which lack a built-in meter, and spot meters measure the light reflecting off a very small part of the scene. Because dark objects reflect less light than bright objects, a reflected light meter can be tricked by an unusual subject or background.

Incident light meters - a handheld light meter which measures the light falling on the subject. Incident meters are not influenced by the subject's reflectance. Many handheld meters can measure both reflected and incident light. Incident meters can be identified by a white translucent dome over the light sensor. A good quality incident light meter can cost a couple of hundred dollars or more.

Measuring the light
Both reflected and incident light meters are calibrated to measure the light in a scene and produce a medium gray tone, the same value which is represented by the gray card.

In a nutshell, a gray card represents the standard reference value which all photo light meters are calibrated against. A gray card reflects 18% of the light which falls upon it.*
The reflected light meter in your camera works well in most picture taking situations but it can be fooled when either the subject or the background is unusually dark or light.

*Short note: We don't want to confuse the issue, but some photographers disagree, arguing light meters are calibrated to 12% gray, not 18%. Here's one opposing view. However, next time you're in a camera store, ask for a 12% gray card and they won't know what you're talking about. Disagreement in photography is the spice of life.

Some examples of tricky exposures
Point your camera at a scene with a lot of snow, sand, water, or sky - the camera doesn't know what it's looking at. Take pictures without adjusting the exposure and you'll get badly underexposed photographs - snow will look dirty and gray, landscapes with big expanses of sky or water will be too dark.

Take a picture of a person standing in the shade with a bright background or with the sun behind them, backlighting their head. This can be very flattering portrait lighting if you know how to use your light meter correctly, but if you don't adjust your exposure to compensate for the bright background, you'll end up with near silhouettes.

You've been given the job of copying some old paintings, old photographs or artwork. How do you properly expose your film to guarantee the copy will match the original?


Solving Difficult Exposures With a Gray Card

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Published February 17, 2000