ExpoDisc Digital Warm Balance Filter

PSA Journal, Jan, 2005 by Stanley B. Ashbrook

ExpoDisc, Inc. introduced their new ExpoDisc[TM] Digital Warm Balance Filter at the PhotoPlus Expo held in New York City this past September. The Warm Balance Filter compliments their current ExpoDisc[TM] that photographers use to establish a precise White Balance at the time of image capture as well as to determine an accurate exposure.

A professional photographer friend of mine has been using the ExpoDisc[TM] to establish a White Balance both for his studio and on location shooting for some time now and says that it saves him hours of post processing computer time.

The new ExpoDisc[TM] Warm Balance Filter produces a White Balance that would be similar if you were to use a Warming filter on your camera lens. In my "film" photography days, I frequently added an 81A Warming filter so as to warm skin tones in portraits and scenery. It was particularly useful in reducing the bluish cast on images shot on overcast days or at high noon and in enhancing sunrises and sunsets. Using the ExpoDisc[TM] Warm Balance Filter, I can not only get this same warming effect but do so with the correct exposure and White Balance.

With my Canon Digital Rebel, I'm currently taking more photographs using Camera RAW. This allows you to adjust both the White Balance and Exposure in the computer. When I open photographs taken using the ExpoDisc[TM] Warm Balance Filter, I cut down on having to make these adjustments, and I only have to provide some minor tweaks, if any. Now I have the option of saving time by opening my RAW images and by-passing the Camera RAW dialog box by holding down the Shift Key. This is also very useful if I want to batch process both Camera RAW and JPEG images.

The ExpoDisc works by installing it on your camera as you would a filter, with the white side toward the lens (see Figure 1). The other side looks to be prismatic and is away from the camera.

[FIGURE 1 OMITTED]

Here's how it works: with the camera exposure and focus set to Manual, point the camera at the light source and adjust the exposure. You'll now get the same result as taking a very accurate incident light exposure reading. Now point the camera at the subject and expose it to record a gray frame with an added warm tone. Use this frame to set your camera's White Balance.

Figure 2 is a shot taken recently on a short vacation to North Carolina. I used Daylight WB and Aperture Priority Auto Exposure. Not only are the cool tones a bit excessive, but also the highlights are slightly blown. Notice the improvement in Figure 3, taken using the ExpoDisc[TM].

[FIGURES 2-3 OMITTED]

One day, I noticed small dark spot on this image and others. This turned out to be a dust spot on my image sensor. To establish if this were true, I used the ExpoDisc[TM] Warm Balance Filter to generate a gray image which made the dark spot stand out. I followed the camera instruction book on how to remove this dust. I then made another gray image which showed that the dark spot was removed. This will now be a reference image to check for possible dust on my sensor in the future.

If accurate exposures and white balances are your goal, then I recommend the ExpoDisc[TM] and its complement the ExpoDisc[TM] Warm Balance Filter.

The ExpoDisc filters work with digital cameras and digital video and are available in six standard filter sizes from 58mm to 82mm. Prices range from $79.95 to $159.95. Also check out their web site is http:// www.expodisc.com/index.html.>

COPYRIGHT 2005 Photographic Society of America, Inc.

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