By: Erik Vlietinck
Sun, April 15, 2007 - 5:17:00
Pros: 0

http://www.expoimaging.net
Score: ">

Perhaps the most difficult part of shooting beautiful colour photos is setting up the camera correctly so that it will “see” colours accurately. The human eye will accommodate to various conditions of light, and even when we see a white wall under greenish fluorescent light, we will still be able to recognise it as white. A digital (and analogue) camera is not that intelligent. It will simply record the light bounced back from the wall, i.e. green. Correcting this is easy with the ExpoDisc.

Most serious amateur photographers and certainly professionals, will calibrate the camera whenever the light conditions change. They will use the camera’s white balance feature to correct for lighting conditions. Traditionally, such a white balance calibration is done using a GretagMacbeth ColorChecker colour chart. GretagMacbeth has a number of these charts, of which the latest and probably the best is the Digital ColorChecker SG. But these charts cost a lot of money and they are bulky to carry with you. A better alternative is to use ExpoImaging’s ExpoDisc, a special contraption to set white balance and do a whole slew of other things.

The GretagMacbeth ColorChecker SG can be used to just set white balance or to calibrate your camera across all colours the chart contains. With it, you can create a camera colour profile. However, most photographers will balk at creating one except for studio environments where lighting conditions are totally under control. When shooting outside or in environments where lighting conditions may change beyond their control, all they can do is set the white balance correctly and take it from there.

Granted, GretagMacbeth and others make colour charts for that purpose too. These colour charts are small, and usually made from a material that will fit a smaller budget. Still, even with these small credit card sized colour charts, it takes a photo shot with the chart right in front of the lens and pointing away from the light source, so that the chart catches all light. Not very handy and even then, errors will occur.

Carefully Crafted, Simply Useful

It is much easier to have a contraption that you just snap onto your lens barrel, that has been calibrated to strict specification, and which allows you to do more than just white balancing.

The ExpoDisc is a disc that resembles a lens filter. It can be attached to the lens barrel. It contains an odd-looking grid at one side and a uniform white surface at the other. It comes in a nice black cardboard box with a lovely little green-and-orange frog painted on the box’s top, a pouch, a chord to attach the disc to so that you can wear it around your neck, a DVD-rom, and a calibration certification card.

The ExpoDisc comes in various lens measures, ranging from 58 mm to 82 mm --for prosumer cameras, ExpoImaging has another (non-calibrated) contraption with clamps that “grasp” the lens barrel. And it’s not new --despite it being a contraption that is only modestly marketed, the ExpoDisc actually was invented by the current Company President’s grandfather, George A. Wallace.

ExpoDisc takes on the assumption that you will not use the camera’s built-in Auto White Balance feature. That is indeed the best to avoid, but with RAW photography it is less of an issue. However, as I could experience myself, even with RAW photographs the ExpoDisc is a true help for very little money, as it does three things well: it allows you to save time by setting an “As Shot” white balance, to see where there’s dust on the sensor, and whether a lens is troubled by serious or reasonable vignetting.

Avoid Auto White Balance

As a rule of thumb, I always set my camera to one of the fixed white balance settings when I go out on a shoot. The Auto White Balance is like a moving target: with every light change you’ll get different results, sometimes even within an interval of as low as a couple of minutes. Additionally, most cameras’ automatic white balance feature is not as accurate as it should be.

So, the rule is to set the white balance to something resembling the lighting conditions of your environment as close as possible. With RAW, it will save you some time when opening the photo in a Camera RAW application. Even then, it will sometimes produce less-than-optimal results with some cameras. The ExpoDisc on the other hand, takes the guesswork out of setting white balance and eliminates virtually all white balance problems by handing to you three methods with which to “calibrate” your photos (I’m deliberately not saying “camera").

The first method that you can use the ExpoDisc with is the equivalent of the GretagMacbeth chart: shoot a photo through the ExpoDisc while pointing it at the most important light source in the scene. Now shoot your photographs and afterwards in Photoshop, you can use the ExpoDisc’s photo as a white balance reference for all the shots taken under the same circumstances.

The ExpoDisc makes this easier because it’s small, hangs around your neck, will fit your lens (or when it doesn’t, you’ll have less difficulties in clamping it manually to the lens than when you have to focus on it by using one hand to hold the chart and the other to press the shutter). You’ll also find the risk of having an over-exposed white balance reference shot to be very small, because the ExpoDisc is not 100% bright white --it has an 18% light density.