From www.stormjacket.com



The WarmCards SLR 2.0 set of white balance cards comprises seven coloured and one white targets, in addition to a Kodak grey card. The idea is that you take a reading from one which becomes your reference point, ensuring consistency from shot to shot as your camera’s auto white balance system isn’t constantly assessing the lighting conditions.

With the exception of the grey card, the targets are coated in a matte-finish plastic to eliminate reflections. They are said to be waterproof and washable, and should withstand being used continuously without any damage, while a nylon pouch is provided to hold the cards when not in use.

Taking a custom white balance reading is a fairly painless process, and so using the cards is a doddle. You simply point and shoot, and then set that as a reference (depending on exactly how your camera sets this). The cards make a noticeable difference to pull an image in a slightly warmer or colder direction, though the beginner may need to trial and error the cards a few times to understand by how much each card will shift the images warmer or colder. It’s also quite handy having a white card among the set, should you set an inappropriate setting and want to set a ‘normal’ reading. 

So, their concept makes perfect sense, but it overlooks the fact that most cameras’ white balance systems are already fairly sophisticated. Many have a Kelvin scale for more precise adjustments, and some even an option to set a slight colour bias for a particular image (more magenta, more green etc). For these reasons the cards aren’t quite as ingenious as they claim to be, and £50 isn’t exactly cheap for what’s essentially laminated pieces of card. Whereas years ago they may have been a convenient accessory, now they just appear as a pricey and redundant one.