A grey card is a flat card in a neutral mid-grey that gives your camera and editing software a known reference. Photograph it in the same light as your subject, then use it to correct color casts and judge exposure with confidence.
What It Does
Different light sources tint a scene: daylight, shade, and household bulbs each lean toward a different color. Because the card is neutral, any tint in its image shows you exactly how much to remove. Cameras also tend to guess brightness from an average, and a mid-grey card is the target that average is built around.
Using It for White Balance
- Place the card where the light falls on your subject, facing the main light source.
- Fill the frame or a good part of it with the card, in focus is not required.
- Take one frame and note which frame it is.
- Either set a custom white balance from that frame in your camera, or later click the grey area with the white balance tool in your editing software.
- Apply the same correction to every frame shot under that light.
Using It for Exposure
Meter off the card in the same light as the subject and set your exposure so it appears as a middle tone. This works well for scenes with large bright or dark areas that confuse automatic metering, such as snow or dark fabric. Some cards also have a white side; follow the maker’s guide for which side suits which task, since the details differ between products.
Handling Tips
- Keep the surface clean and free of fingerprints, and avoid bending it.
- Avoid glare by tilting the card slightly if the surface reflects a light or window.
- Store it flat in a pocket of your bag away from sunlight, which can fade materials over time.
- Re-shoot the card whenever the light changes, such as when clouds move in or you step indoors.
Many photographers also place the card in the first frame of every new location or lighting change. When you sort pictures later, that frame acts like a marker, showing where one lighting setup ends and another begins. In video work the same idea applies: a few seconds of footage of the card at the beginning of a take provides a neutral reference for color matching later.
FAQ
Is a grey card necessary for every shoot?
No. For casual pictures, automatic settings are fine. It earns its place for product work, copy work, and any set where color must match from frame to frame.
Can I use something grey from around the house?
You can try, but many surfaces carry a slight tint. A purpose-made card is more reliable.
The Short Version
Shoot the card in the same light as your subject, then use that frame to set white balance and check exposure. It is an inexpensive habit that saves editing time.