Tech Check Grey card
This accessory from the days of film maintains its relevance today
What is a grey card?
It’s a simple accessory intended to help you get an accurate exposure. Available in all shapes and sizes, the grey area is a very specific grey that reflects 18% of the light falling on it. This is exactly halfway between black and white, so it’s an official midtone. This is what a camera’s light meter uses to measure the brightness of a scene or subject.
How would I use it?
To determine the correct exposure for a shot, all you have to do is place a grey card in the same light as your subject, and spot-meter from it. This will give an accurate exposure.
If you set Aperture Priority mode, dial in your preferred aperture and point the spot meter at the grey card, then the shutter speed you’re given is what you should set for that scene in that light.
I can see an instant result on my digital camera, so is having a grey card as important now?
With both a rear screen and a histogram display, and the fact there is no extra cost for shooting additional frames either side of your best exposure, the grey card isn’t as essential as it was in the days of film, although it can be useful for getting accurate colours. But because a grey card is perfectly neutral, it can be used as a reference point for accurate colours.
How do I do that?
Either use the grey card as the reference point for the setting or – more commonly – do it later in raw conversion software like Camera Raw or Lightroom. Place your grey card in the scene and take a reference shot using your camera’s raw format, then withdraw the card and shoot your pictures. When you’re making your raw conversions, you can use the grey card shot as a white balance reference by utilising the White Balance Eyedropper Tool.