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expodisc - a small,lightweight and very useful little tool
It is called Digital White Balance Filter, it is not expensive, small, round, lightweight, easy to use and I found it very useful and practical for white balancing in color photography. What is it really? Well, it is just a filter, but a rather intelligently designed filter, consisting of several layers of material of different absorption and shape - the top layer on one side looks like white plastic and the one on the other, outer side looks like an array of transparent macrolenses - as a package, it acts as an ND (gray) filter with 18% transmission. The small lenses on the outside of the filter collect light from a wide range of angles and scramble the color information completely to get a pretty homogeneous light flow into the camera. This light can now be used to set it to neutral - most of the time it works very fine but of course, as with all technical aids, there are limitations as well where the intelligent mind of the photographer cannot be replaced by any tool. The results of using this device are impressive and it is much more convenient to use this tool than a standard gray chart - here a few results to show the difference with/without the expodisc: The first shot was taken in the Botanical Garden in Denver/Colorado, in the tropical green house - the shot with the standard white balance is very good already but if you look closely at the non-green details, they are not really neutral. Using expodisc changed this situation - the overall impression is now that the green leaves are nicely green and realistic and the other details do not show any color shift anymore - nice result
The second example are two shots taken at the South Platte River, South of Denver. It was a sunny day (what else can it be in Colorado....) and here again - the one which was taken without the expodisk shows a sky which is slightly tinted - a tint, which is gone completely after correcting the white balance with that expodisc.
I do agree that the difference between these two shots are not very significant but still visible - in the original file, they are much more visible than on the compressed comparison file, but that is a fact for most web related images - they loose much of their significance after compression, making them small enough for uploading etc. Another interesting situation was just outside of my apartment - the sun was shining at the house in front and the combination of sun and blue sky made the photograph with the automatic setting appear quite cool - but in reality, it was not that cool at all. Using expodisc changed the color rendition significantly and the outcome represents the subjective impression I had - a warm sunny morning. The colors represent what I had seen - the sky was not clear blue (yet) and the front of the house looks more correct as well.
Not all lighting situations are suitable for the expodisc - one example: Indoor lighting of a room - usually one would like to express the mood of the room by keeping the warm tone of the light. In this situation, the white balance expodisc is neutralizing the warm tone and the resulting photograph looks cold - neutral white but cold. Such situations need either the warm-tone version of the expodisc (which is available) or a custom set white balance which retains the warm tone of the light. My conclusion is that for many, very many situations which benefit from a more customized white balance setting, the little expodisc is a very valuable tool which is easier to take out than a gray chart. This device is available in many sizes and shapes - more you can find on the website of the manufacturer, ExpoDisc How to apply and use the white balancing with this little device - you find for most available digital cameras the precise information on the website of the manufacturer. For Photoshop users, there is also an article on that website how to use it for raw files, so no need to explain it again here, just visit the ExpoDisc website
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