What is a gray card, and how can you use one in your photography?
In this article, I’m going to address all things gray-card related. I’m going to share the purpose of a gray card, when it’s needed, and – most importantly! – how to use a gray card for beautiful exposure and colors in your photos.
These little accessories start at less than $10, yet they give you a huge amount of control over your images, and they can be invaluable in tricky situations.
So to master gray card photography, read on!
What is a gray card in photography?
A gray card is exactly as it sounds: A card that is gray. More specifically, a gray card is generally middle gray, or 18% gray. They tend to be small, portable, light, and easy to whip out of a camera bag when necessary.
Certain types of photographers never photograph with gray cards, such as street photographers, wildlife photographers, and (most) landscape photographers. But other photographers, including portrait photographers and product photographers, rarely leave home without one. Why? I explain that in the next section:
Why are gray cards important?
Remember how I said that a gray card is middle gray, also known as 18% gray?
This number is important because 18% gray is what your camera’s meter is trying to calculate when it determines a correct exposure for a scene. If you put a gray card in front of your subject and take a meter reading, you will get a balanced exposure regardless of any tonal contrast in the scene.
Now, you might be wondering: What about my camera’s meter? Why can’t I rely on it for a good exposure?
Camera meters are very, very good, but they make mistakes, especially when faced with significant tonal contrast, as well as scenes that are naturally very light (e.g., a snowstorm) or very dark (e.g., a black rock).
The scene below is a tricky one for a camera meter to handle, thanks to the bright highlights on the food and the dark wood of the table:
Gray cards have a second important use:
They offer a completely neutral surface for white balance calculations. Unlike most colors in a scene – blues, yellows, greens, etc. – a gray card has no natural temperature or hue. So by training your camera on a gray card, you can set a perfect white balance for everything you photograph. This is particularly important when you need to faithfully recreate colors in your images, either for commercial purposes or scientific/record shots.
Although the basic white balance settings in cameras can be pretty good, they do tend to struggle at times. For example, tungsten bulbs can vary greatly in color temperature, depending on their quality and power output. This may lead to the tungsten setting on your camera failing to give you an accurate representation of colors, hence the need for a neutral gray card.
Do you need a gray card?
Gray cards are helpful, but they don’t work for every type of photography. For one, if the subject is moving, then a gray card calculation is essentially worthless; within a few moments, the scene will change, and you’ll need to take another reading, and another, and another, which is more than a little annoying. Imagine a street photographer, who goes back and forth from shadow to sunlight while photographing subjects on the move. A gray card would be useless, as the exposure and white balance would need recalibrating from moment to moment.
Additionally, a gray card only works if your subject and the gray card are illuminated by the same light. Yet in certain genres of photography – bird photography and sports photography, for instance – the subject may be far off in the distance. That’s why bird photographers and sports photographers pretty much never use a gray card; there’s really no point, given the distance to the subject!
On the other hand, gray cards are perfect for controlled shooting scenarios. If you’re photographing food, products, or portraits, then a gray card is incredibly helpful. You can get close to your subject, take a gray card reading, and rely on it for an entire shooting session. Plus, gray cards are often necessary in these scenarios, as you must accurately represent the product and food colors.
How to use a gray card for perfect exposures
A gray card is the closest thing you’ll get to a magic bullet; it will give a near perfect exposure in almost any situation. So how does it work?
First, set your camera to spot metering mode, which tells your camera to meter off a small spot in the center of the frame. While this is not absolutely necessary, it will help a lot, especially in circumstances where you cannot fill the entire frame with the gray card.
Next, put the gray card in your scene, right at the center of the frame. Switch your camera over to Manual mode and set the exposure (based on your camera’s meter reading).
Then take the gray card away. As long as the light doesn’t change, you will now have an accurate exposure for all subsequent shots you take of the scene.
Easy, right?
Metering with a gray card: quick tips
Here are a few hints to make the gray card metering process easier and more accurate:
First, after metering, make sure that your subject remains in a similar position relative to the light source. For example, if you’re taking headshots outdoors and the sun is lighting your subject from the front, make sure your subject stays frontlit. If you turn your subject to the side, turn completely around, or head into the shade, that will affect your exposure and you will need to take another gray card reading.
When you’re taking the meter reading, fill the frame with the gray card as much as possible. This will ensure that your meter only exposes for the card and not anything around the edges.
How to use a gray card for a perfect white balance
There are two ways to set your white balance with a gray card:
First, you can set your camera’s custom white balance.
Second, you can use Lightroom (or your favorite post-processing program) to set a white balance for your images (though thanks to the gray card, the white balance will be consistently perfect).
Method 1: In-camera custom white balance
The technique described here is for Canon users. If you use Nikon, Sony, or any other brand, you will need to consult your manual for instructions on setting a custom white balance, though the process will be somewhat similar.
- Take a photo of your gray card. Try to make sure that the card is flat and that it is lit evenly. It should completely fill the frame and mirror the positioning of your subject.
- Open your camera’s menu and select the option labeled “Custom White Balance” (or Custom WB). When prompted, choose the photo of your gray card. Set the camera’s white balance to use the new custom setting and start taking photos.
Note: If the lighting or direction of your scene changes, just repeat the steps above. All of your images will have an accurate white balance!
Method 2: Post-production custom white balance
For this white balancing method, you only need to do one thing with your camera:
Take a photo of your gray card before shooting each new scene.
(It may help with organization if you start off any sequence of photos with the gray card image. This way, you will always know which image to use for a white balance setting.)
So if you’re photographing a food photography setup, you’d place a gray card in the scene, take a single shot, then continue on with your photography. If the scene or the lighting changed, you’d add the gray card once more, take a shot, and so on.
Many photographers use a ColorChecker Passport for this type of white balance process:
Note that the gray card doesn’t need to fill the frame; it just needs to be present in the shot. So you can set up your entire scene, put the gray card in front of your subject, then take a single picture.
Once your photoshoot is complete and you open up the images in Lightroom, the steps are quite straightforward:
Step 1: Select the photo of a gray card and enter the Lightroom Develop module:
Step 2: Select the eyedropper tool in your White Balance settings. Click on the gray card in your photos. This will adjust the white balance for a perfect result.
Step 3: Press Ctrl+Shift+C to copy your settings (Cmd+C on a Mac). Check the White Balance boxes, but leave all of the other boxes unchecked.
Step 4: Select all of the photos you want to correct, then press Ctrl+Shift+V to paste the white balance setting (Cmd+V on a Mac). Now all of photos you took should have a corrected white balance!
How to use a gray card: final words
All of the techniques outlined here are simple and quick, yet they offer a huge amount of control over your exposure and white balance. That’s why a gray card is one of the most cost-effective accessories you can buy!
So if you don’t yet own a gray card, considering grabbing one. And if you do, go ahead and practice these techniques! Test the gray card out for yourself! You’ll love the results.
Now over to you:
Do you plan to use a gray card? Which of these techniques did you like best? Have you done gray card photography before? Share your thoughts in the comments below!
