Erik Moore wrote: speedtrap wrote:
This may be stupid, but I do not carry a white towel around with me.
Sure- practical matters aside, I\'m asking from a technical perspective. I know a grey card will fit in your wallet, and a towel won\'t. Just wondering if 18% grey is better technically than white with details.
Thanks for your input.
Erik,
Grey cards serve two very different functions in the digital world. First, is for exposure as in the film days. Second as a White Balance tool. Larger collapsible cards can even offer a third function as a reflector or cutter.
From a WB standpoint there are indeed some technical differences, as small a they may seem. Most (not all) digital grey cards are a true neutral RGB, where the component color values (Red, Green, Blue) are equal. Most white cloth, including terry cloth towels and T-shirts, have brighteners in them. Brighteners increase the blue component of the RGB values, resulting in a slight color imbalance that is visible to the camera, if not our eye.
Although different camera companies recommend either white or grey for white balance calibration, both will work as a WB reference because they are both monotone colors. Grey tends to handle a wider range of exposure variation because it is mid-tone.
Although it is not as color accurate as a true digital grey card, terry cloth certainly can work as a WB tool , but it\'s main benefit is more as a exposure tool than a WB tool. Terry cloth works extremely well as a highlight warning indicator where texture helps to establish the point where highlight detail is lost.
The value of a \"grey\" card in the digital world may be as debatable as a light meter, but as a \"workflow\" tool it certainly has it\'s place, particularly if you are shooting processed images, such as JPEGs. I personally find a good quality collapsible grey card with white back to be a invaluable WB/Exposure reference tool and a handy fill card/ reflector as well. But when ever necessary, I won\'t hesitate to use whatever is available to me. Even in my film days, I\'d use the back of my hand instead of a grey card if that\'s what it took.
The most important thing is to know your equipment, have a consistent workflow and incorporate tools that maximize your efficiency and effectiveness in achieving your goal.
Good luck.
Oct 20, 2009 at 12:20 PM
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