White Balance with the ExpoDisc
By James Menges
4 Nov 2008
Digital SLR cameras have given us greater flexibility to deal with light color temperature and white balance control because they can process image data for a variety of different color temperature conditions. Today's cameras have a multitude of White Balance control settings including Auto White Balance, Pre-set (Incandescent, Florescent, Sunny, Cloudy, etc.), and custom controls and settings. Experimenting with White Balance settings can result in a range of effects, making it just as easy to distort natural light as it is to capture it. Setting the camera on Auto White Balance gives reasonable results, but is sometimes far from optimum settings. The resultant unnatural red, yellow or blue tints are time consuming or impossible to correct in post-capture software on the computer.
An ideal solution is to White Balance your camera for each shooting condition using the ExpoDisc Digital White Balance filter. The ExpoDisc, which is made by Expo Imaging, is easy to use with any digital SLR that allows custom White Balance settings.
The ExpoDisc turns your camera into an incident light meter, enabling direct measurement of the light source. It should not be used to read reflected light off your subject, but should read the light that falls on the subject. You point the camera at the light source you are trying to balance.
Available in standard sizes from 52mm to 95mm, the ExpoDisc snaps onto lenses, so there is no need to fumble with a screw thread each time you use it. You can get the size for any specific lens, or buy for the largest lens you have, which can be held in front of the smaller lenses during the calibration process.
The ExpoDisc is more convenient than using a grey card for White Balance. Since it covers the lens you don't have to worry about filling the frame, card angle induced reflection, or dealing with cumbersome grey cards. As long as you can operate the White Balance custom setting features on your camera, you can use the ExpoDisc.
There are just a few simple steps to use the ExpoDisc:
1. Determine what your shot will be. Identify subject position and direction of light source. Set the camera for how you will take the photograph: ISO, aperture, and shutter speed.
2. Install the ExpoDisc on your camera lens, and set the camera to Manual Focus. (the camera may not be able to auto-focus with the Expodisc on which prevents some cameras from capturing an image)
3. Set your camera's White Balance custom controls. This process is specific for each camera make and model. Refer to your camera's operating manual or refer to ExpoDisc's DVD or website for details on how to set a custom white balance on your camera.
4. Position the camera to where your photographic subject is located, and point the camera at the light source. Press Shutter release, which will capture the White Balance setting.
5. Remove ExpoDisc. Reset camera to auto-focus if desired, and take the photograph of your subject.
I used ExpoDisc with my Nikon D80 under various conditions, and compared against the Auto White Balance setting. When shooting outdoors in bright sunlight, the Auto White Balance control closely approximates a natural image. When taking pictures in the shade or at the extremes of daylight, the proper White Balance settings achieved with the ExpoDisc brings out richer colors. When shooting under Tungsten lights, the Auto White Balance completely misread the color temperature for both the still life and portraits. I was able to manually experiment with the White Balance control settings on my camera to get a neutral balance for the studio lights, but it was faster and easier to use the ExpoDisc and take a single setup shot.
The ExpoDisc comes with a neck strap for easy use in the field, a case, a Quick Start Guide and DVD with tutorial video clips and White Balance setting guides for most cameras.
The ExpoDisc is available on-line and at leading camera stores. Like many products, I found a big disparity in prices at retail outlets. I ended up ordering from the manufacturer on-line and promptly received my product within 3 days. Prices range from $69.95 to $169.95. For more information on the ExpoDisc check out Expo Imaging's website at www.expoimaging.net
The ExpoDisc is easy to use, works in mixed and difficult lighting situations and saves you time in post-capture adjustments on the computer. It is a valuable tool to have in your camera bag.