How to use a gray card to meter exposure (and 4 other photo uses)

Did you know that a photography gray card has a second purpose? Apart from setting white balance, gray cards in photography are helpful for setting exposure accurately. If you’re a natural light photographer, and you don’t already have a gray card, this’ll show you how necessary they are.

Before I get into why you need a gray card, I’ll start by saying that it won’t break the bank. You can pay as little as $9.99 for this lightweight tool and it’ll improve your photography instantly.

If you’re wondering what type of gray card is the best one for portrait photography, keep on reading or scroll down, I’ll show you the one I use and recommend.

PS:  This post contains affiliate links. Buying something through one of the links won’t cost you anything extra, but I may get a small commission, which helps to keep the site running.

Why use a gray card for metering exposure?

When photographing with natural light and using your camera’s reflective light meter, instead of a handheld incident light meter, a gray card is helpful for accurate exposure readings.

Difficult exposure conditions

Gray cards are especially helpful when faced with difficult lighting conditions or high contrast scenes, like:

  • Photographing in snow, or on a sandy beach
  • Wedding photography when the bride is in white and the groom in black

Why a gray card helps with exposure metering

Exposure metering, and getting exposure right, is a major part of photography (obviously), so it’s one of the two subjects with the most questions.

The other is focus (and I have a focus trick for you further down). There’s also a lot of confusion and wrong information given out about exposure metering, which makes it even more difficult. So, sometimes I think exposure metering is more complicated than it needs to be.

Using a gray card simplifies exposure metering

Because a gray card is medium gray, the tone your camera considers the correct exposure, metering exposure off it will give you an accurate reading. You won’t need to:

  • Look for something in the scene that’s medium gray to meter exposure (like green grass), or
  • Use exposure compensation, or
  • Consider the zone system to determine the level of exposure compensation required. 

How to use a gray card for exposure metering

As I said, a gray card simplifies the process of metering exposure, so here’s how to use it to measure exposure:

  • Either place the gray card in the scene you want to photograph or
  • Ask your subject to hold the gray card up next to their face, pointing back at your camera
  • Fill the frame with the gray card for an accurate reading
  • Meter the exposure using spot metering
  • If in manual mode, adjust your aperture, shutter speed and ISO accordingly
  • For aperture priority mode, or shutter priority mode, set either your aperture or shutter speed, check the camera’s respective setting for either shutter speed or aperture. Lock the exposure
  • Remove the gray card from the scene
  • Take lots of great, correctly exposed photos!

As long as the lighting conditions stay the same, your camera settings can stay the same for the rest of the photoshoot. You won’t need to change your exposure settings, unless you want to change either the depth of field or the shutter speed.

Obviously, if you move from that location or the lighting conditions change, such as the sky becoming overcast or the sun starting to set, meter your exposure again.

How a gray card helps with exposure metering

The subject has a light complexion, so metering off her cheek would give an inaccurate exposure setting and the photo would be 1 stop underexposed. Holding a gray card next to her face to meter off would ensure accurate exposure settings

3 other gray card uses in photography

If you’re not already convinced that your life would be easier with a gray card, here are 3 other ways they’re incredibly useful.

1. Use a gray card to focus

Using a gray card to focus is a relatively unknown use, but it’s a great one!

Have you ever wanted to preset your camera’s focus so that you can take a selfie? What about if you want to use autofocus to focus and then switch to manual as neither the camera nor the subject will be moving? 

You might not do this often, but when you do, wouldn’t it be great to have a handy target for your camera’s autofocus to lock onto?

Some gray cards have exactly that at their center!

Because your camera needs contrast to focus, the target on the gray card makes it easy for your camera’s focusing system to lock onto.

2. Use a gray card to prevent lens flare

If the sun is at too much of an angle for your lens hood to keep light from hitting the front of the lens and causing lens flare, some types of gray cards are a really handy to hold over the front of your lens for shade.

3. Use a gray card as a reflector

Many gray cards have white on the reverse side. In a pinch the white side becomes a handy little reflector for filling shadows. Obviously, as it’s small it’s not good for large subjects, but if you’re photographing something small and need to lift the shadows, the white side is useful.

Exposure metering with a gray card

This gorgeously goofy dog belongs to the girl above. Because I’d already metered my exposure from a medium gray surface (green grass is ideal), it was easy to get an accurately exposed photo of him too in the same location, even though he’s dark and she’s very light. He would have confused the camera’s exposure meter, which would have resulted in my photo being 2 to 3 stops overexposed, if I’d believed the camera.

What’s the best type of gray card to get?

Even though it’s a small investment, not all gray cards are a wise buy. Some might seem like the most convenient choice, but they don’t work as well as others.

After reading about how to use a gray card, you might think that it’s not exactly a technical piece of equipment, so what difference does it make what type I use?

Well, most gray cards are perfect. Just don’t get one that’s too small. It’s so much easier to meter your exposure off something that can easily fill the frame when you’re close or you can easily spot meter off from a distance.

Also, if you want to use it to lock focus, you need one with a target in the centre, rather than a plain gray surface. 

The type of gray card I use and recommend

I use a Lastolite Ezybalance gray card, which I bought about 8 years ago, but you don’t need to spend nearly $40. This one is a much cheaper option that looks the same and is just as good, but costs less than a quarter of the Lastolite one.

As you can see this isn’t an actual card, it’s like a small fold up reflector. You can get actual cards, but they’re often too small, are less durable and oddly often cost more.

Summary – why you should get a gray card

I don’t advocate buying all the gadgets on the market, which is why I don’t do many gear reviews. Photography is expensive and your camera bag is probably heavy enough as it is, but some tools just make sense.

If you’re not already convinced, here’s a summary of why you should get a gray card for photography:

  • Set white balance, especially with a custom Kelvin setting
  • Meter exposure accurately with all types of light
  • Lock focus in low light conditions or for selfies
  • Shade your lens to prevent lens flare
  • Use it as a reflector for filling in shadows
  • Gray cards are small, lightweight and fold up easily
  • Gray cards are cheap

Leave a comment

If you have any questions about using a gray card for exposure metering, let us know in the comments.

Also, I love good news, so if my photography tips have helped you, share that too.

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