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Solving White Balance Issues With the ExpoDisk

by Chris Gampat on 06/08/2011

“I want to get it all right in camera,” is a statement made by many photographers and is what many actually strive for but sometimes fail at. The ExpoDisk was designed to help remedy those problems just a little bit with white balancing issues. As a cost-effective and highly portable option, it has very quickly become an item that I never forget in my camera bag.

What is the ExpoDisk?

The ExpoDisk is a portable little disk that attaches onto the front of your lens and helps you to calibrate your white balance in camera. Theoretically, it will provide you with much better color temperature readings and also much more true to life images. There are two sides to the disk: one with a surface that looks crystalline in structure and the other which is smooth and white.

To use the disk, one needs to make the white side face the front element of their lens, aim the camera and lens at the primary light source, shoot the image, set the white balance to custom, and then white balance off of said image. Here’s a quick demo video I did to show how to do this.

How White Balance Works

To understand how the disk works, one first needs to understand how white balance works. Take a look at the color wheel above. Now imagine that you were shooting in an environment that was mostly dominated by Orange-Yellow light. In order to neutralize the light and obtain ideal color balance, you’d need to add some blue-violet. In the digital world, all you need to do is set your white balance to the appropriate setting. This is much easier than back in the film days where one needed to get color balanced film.

To make a long story short, your camera’s white balance works in an inverse relationship to the light. If you’re shooting with your flash (which outputs very cool light around the blue color) then you’d want to set your camera’s white balance to lean more towards the orange side of things.

This is relative though as advanced white balancing techniques I feel are done in Lightroom 3 and with balancing off of what is called Middle Gray. This is where once finds RGB pixels are close to 50% and the entire image is balanced off of said pixels. This effectively color neutralizes the image and delivers more accurate colors.

Test with Flash

First up, I tested the ExpoDisk with my Canon 7D, 35mm F/1.4 L, 430 EX II and the GoPro Ring Flash Adapter. When shooting with flash, one can assume that this will be their primary light source. When using a flash modifier, one can often get some very quirky results with the ExpoDisk. Indeed, I wanted to use the Ring Flash adapter to photograph the images of the ExpoDisk for this story. So I used to disk to balance my image first by aiming the camera at the 430 EX II with GoPro attached.

The images came out too cool for my liking. However, this wasn’t the end of the test, I decided to try out the 7D, 35mm and 430 EX II with the flash mounted on top. This time though, I aimed the flash directly at the ceiling light in my room, which delivered a very warm light output. On the opposite end of the spectrum, all flashes are balanced to daylight, which is very cool lighting. One of the biggest challenges I often face is shooting with mixed lighting.

So this was the image I balanced off of.

This was the result with custom white balance. Note that for all of these tests, the flash was aimed towards the ceiling.

This is the result I garnered with auto white balance: which is much closer to what would have come out of camera if I had balanced off of the flash to begin with. The reason for this is because of the flash’s cool light output, the camera forces itself to balance the image to be warmer to deliver more life-like color.

Take a look at the histograms in the top right corner.

This image is leaning more towards the bluish side.

And this image is leaning more towards the warmer (orangish) side. As you’ll notice, the bluish image is also skewed more towards the right of the histogram and is also yielding a much more balanced exposure despite both images being shot at the same exposure settings.

So I decided to redo the test and then also show off color neutralizing using the Middle Gray pixel finder method.

The photo above shows custom white balance and once again portrays cooler tonality.

Meanwhile this image displays a warmer tonality and once again what would be achieved if one were to balance off of the flash (this was tested later on by myself to make sure that I wasn’t going crazy). What would happen if you color neutralized it using the middle gray method?

Middle Gray balance (color neutralized)

You’d end up with an image that looks like the above. Here are the other two images for reference.

Custom White Balance

Auto White Balance

As you can see, neutralizing the color yields an image that is a perfect balance of the two. So far the ExpoDisk is giving me results that can be close, but I’m also still finding that the Middle Gray method is still the best and the the disk just makes the post-production process easier.

Test without Flash

My test with the Olympus EP-2 and 17mm F/2.8 took place in the basement of a cafe and the same testing procedures were repeated.

With Expodisk

Without Expodisk

Color Neutralized in post production

With Expodisk

Without Expodisk

Color Neutralized in post production

Conclusions

For the most part, I believe that the Expodisk can get the color balance of an image to be reasonably accurate, although I’ve still proven that the ultimate way is to color neutralize the image in post production. Will it provide JPEG shooters that don’t want to do any post-production with a better alternative to their camera’s automatic white balance algorithms? Absolutely! In fact, if you’re a JPEG shooter there is no reason why you shouldn’t have one in your bag.

For wedding and event photographers, I’d say you should also snag one for yourself unless you want to spend extra time editing hundreds (and sometimes thousands) of photos.

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