ExpoDisc sent me the appropriate size ExpoDisc filter (72mm diameter) for my 28-200mm Canon EOS Lens which I used on the Canon EOS-10D to test this product. To use, you just place the ExpoDisc filter on the front of the lens, as you would the lens cap. While the filter comfortably fits the lens it wasn't as snug as the original lens cap and a few times it popped off while traveling. I'd like to see a squeeze mechanism similar to that used by Canon instead of the three small nubs that are currently being used. I'd also like to see the product ship with its own protective lens cap since the Canon lens cap didn't "grip" well inside the front of the ExpoDisc filter, resulting in the loss of the cap during my testing. This really isn't a problem while using the product as much as it was when traveling with it. The filter never came off during shooting and it includes a 6" tether that you attach to your camera so that you'll never drop or lose it.

How to use the ExpoDisc

The ExpoDisc works with any digital camera that can accept one of the filter sizes available (see bottom of review for sizes available) and allows you to manually set the white balance.

There is something I'd like to stress, and this is true of most products, and that is to READ THE INSTRUCTIONS if you want to get the most out of a product. In this particular case, the instructions are very short, can easily fit into your pocket, and contain important information relating to setting the white balance.

There are two methods for setting the white balance using the ExpoDisc. The Incident Method should be used when there is a single dominant light source, while the Reflective Method should be used when shooting in mixed lighting or when you cannot get an incident light reading.

When using the Incident Method you should stand next to your subject (or in similar lighting) and aim the ExpoDisc (while on the camera) away from the subject toward the dominant light source. This will provide an accurate white-balance reading for the subject you're about to photograph.

When using the Reflective Method you would aim the camera (with the ExpoDisc on the lens) toward your subject in order to get an accurate reading from the mixed light sources that are hitting your subject.

These are the steps to getting an accurate white balance using a Canon EOS-10D.

• Place ExpoDisc on front of lens (take of original lens cap)
• Turn off the autofocus by moving the switch on the lens assembly
• Set the camera to Manual mode
• Aim the camera at the appropriate light source
• Adjust the Aperture and/or Shutter until the translucent gray cap is properly exposed
• Take one picture of this gray image
• Press "MENU" on the back of the camera , scroll down to "Custom WB", click "SET" (middle of rear dial)
• The gray photo you just took will appear. Click "SET" again to tell the camera to use this photograph to set the white balance against
• Switch to shooting mode. Then press the [AF-WB] button on the top of the camera
• Use the rear dial to select the custom WB graphic
• Take the ExpoDisc filter off the lens, frame and shoot your subject

The All Important "Does It Work" Test

This example illustrates a very common type of photograph. An indoor picture with a lot of outside light coming in through the windows. The photograph on the left was white-balanced using the ExpoDisc and shows warmer, more natural tones compared to the image on the right which was captured using the Automatic White Balance (AWB) of the camera.

This comparison was shot under a partly cloudy sky. The Exposure and White Balance for the picture on the left side was set using "The ExpoDisc" while the picture on the right was taken with the Canon EOS 10D set to Automatic exposure and White Balance. Again, the ExpoDisc-balanced image offers a more natural tone. The shrubs and brick show their natural color compared to the image on the right which was captured using the automatic settings.

In this example, you can see that setting the white balance using the ExpoDisc filter helped to bring out subtle color in the flower pedals when compared to the same photo taken with the camera set to AWB (Auto White Balance). It is small differences like seen in this example, or larger variances like shown above, that make using the ExpoDisc worthwhile.

Conclusion

The ExpoDisc isn't inexpensive, and it isn't for everyone. However, if you take your photography seriously, either as an enthusiast or professional, then I highly recommend having this tool within reach. The ExpoDisc will make a difference in your photographs especially when lighting conditions get tricky. It is simple to use, offers better accuracy than using a gray or white card, and can save you countless hours of post-processing when your camera's white balance didn't get the job done.

Nothing's Perfect

I would like to see ExpoDisc offer a better (tighter) mounting method as well as its own lens cap. This would allow you to keep the filter on the camera without fear of it falling off and exposing both the lens and/or filter to damage.

UPDATE (11/03/2004): ExpoDisc now ships the ExpoDisc white-balance filter with a neck strap, giving users the option of keeping the white-balance filter around your neck or under your jacket. This eliminates the need to keep it tethered to the camera while keeping it on-hand and ready to use anytime you need it. With this solution you can still use the original lens cap that was included with your camera without fear of it coming loose if the fit isn't snug on the Expodisc white-balance filter.

Pricing

Prices range from $79.95 - $159.95 depending on the filter diameter needed for your camera. The ExpoDisc White Balance Filter is available in the following sizes:

• 49mm ($79.95)
• 52mm ($79.95)
• 55mm ($79.95)
• 58mm ($109.95)
• 62mm ($119.95)
• 67mm ($119.95)
• 72mm ($119.95)
• 77mm ($139.95)
• 82mm ($159.95)