Expodisc white balance with the KM Dynax 5D

The custom white balance function on the Konica Minolta Dynax 5D could not be quicker to use; turn the left hand top dial to the custom symbol, press the button in the centre of the dial, press the shutter after aiming the camera at your white or grey target. Custom WB is now set until changed with a new reading, or returned to fixed or Auto WB.

Many DSLRs have a two or three step process including menu accessed ‘buried’ commands, but in future we can expect to see more designs adopt this simple external control approach and ‘one press, one shot’ sequence (this article was written in October 2005 for f2 magazine – my prediction didn’t come true and the KM 5D remains one of the fastest DSLRs for getting a custom WB entered!).
The main delay then encountered in getting a custom WB is going to be finding your white or grey target, placing it at a suitable distance, framing it and shooting the measurement exposure.

Here, the ExpoDisc Digital White Balance Filter from Expoimaging (distributed by Flaghead – www.flaghead.co.uk) provides a rapid failsafe solution. Just clip it into the lens filter rim, aim so that the prevailing light on the camera is similar to that on the subject, and fire.
It is not actually quite so easy. The opal filter can set AF hunting backwards and forwards, so you must be able to press a button to turn off AF, or set the camera to ‘shutter release priority’ so a firm press on the shutter button fires it whether or not the AF has locked on. You must also be able to remove any lenshood, or work without a hood. We used a Sigma 70-200mm f/2.8 EX DG lens with a 77mm fit ExpoDisc, and it was not practical to juggle the hood and the attachment, despite the neck lanyard for the ExpoDisc.
Each different filter thread of lens might require a separate ExpoDisc, and at prices from £70 including VAT (58mm, the cheapest size) that could be prohibitive. There are some digital lenses which will have cost you less than this device. It is certified for colour transmission and made with professionals in mind – the kind of who once would have used a colour meter, done clip tests of their E6 stock and fitted CC correction filters.
As to whether it works, even a quick test in typical outdoor garden conditions showed that the standard ExpoDisc gathered and corrected the green reflected light from foliage and grass. The improvement in skin tones from this is visible in JPEG shots; those who shoot RAW would presumably be able to make corrections by eye when converting. Here, again, you get this slight glitch in the marketing concept – the sort of user who spends £70 to get white balance perfect also tends to prefer RAW to JPEG.

The KM5D daylight preset shows a subtle green tinge to skin tones from surrounding foliage
There are times when JPEG is essential, and RAW+JPEG can only be made more useful by having an optimum colour JPEG.

The standard Expodisc JPEG is just that bit warmer, removing the green cast by rebalancing the WB
Expoimaging make both a standard and a Warm version, intended for portraits. I found from the test shown below that the Standard actually gave a better neutralisation of green casts on skin than the Warm. The Warm component added a yellow shift rather than a magenta one, and yellow can emphasise green.

The Warm ExpoDisc JPEG adds a yellow warmth – this does not lose the slight green tint most visible round the mouth, and a pink warmth would have been preferable in this situation where the cast to be removed is greenish. It’s still preferable to the rather cold greenish original shot on daylight WB.

Many popular DSLRs have a pinker skin colour than the Dynax 5D; a lack of yellow strength is typical of CCD and CMOS Bayer sensors and using a yellow warmth makes sense. With the Konica Minolta camera used for the test yellows are in no way lacking, and a pink warmth (like a Haze 1B filter) would have been preferable.
Whatever the case, it works and there is no doubt that a custom white balance does improve outdoor skin colour. For some users that alone will justify the cost of one of these simple precision accessories.
Thanks to our daughter Ailsa for surviving yet another job as a test-target!
– DK