gray card question

[pasknucklehead]

Hi guys, just starting to learn white balance with my new gray card. Pretty much have it figured out, but was wondering something simple, how big does the card have to be actually? I got an 8x10, but can't imagine having to haul that size around with me. I know it has to measure the same light as what I am shooting in, and I know I must shoot directly at the gray card, but am I correct in saying that the card must fill up the whole screen in my viewfinder for it to be accurate?
Thanks everyone, oh, something else, now say I was to photograph something pretty near me, and something further away, will the gray card also take into consideration the distance and the lighting be the same further out than just doing a portrait photo? Thanks
DC

[reval8r]

An 8x10 gray card is plenty big enough, DC. It doesn't have to fill the whole view finder screen, but most of it. What I like better is digital calibration target. The better ones can be folded up and put in your pocket or stored away easily in your camera bag.

Here are a couple of reasons I like the targets better, they are a true 18% gray, it’s almost impossible to find a card that is true. With the target you not only have gray, but a neutral white and black as well to verify your exposure with the camera’s histogram. With digital, this is important so you will not be blowing out highlights. The gray card with help with white balance, but leave some guessing about the exposure. If you are shooting something that is white and exposing off a gray card, the white will be gray unless you compensate for the exposure reading.

Also, I wouldn’t get too hung up on making every image with the correct white balance. Setting the correct white balance on that truly beautiful sunset will kill the mood you saw when you took the image. It would take away that nice warmth for those beautiful orange, red and gold tones.

Play around with different white balance settings under different lighting conditions to see what you get. Examples, I shoot most outdoor portraits with a white balance set in cloudy mode and most night shoots with a tungsten white balance. In studio, I shoot most portraits with a custom white balance off the target.

I generally only use a target on portrait or product photography. I find these the most critical to get right. I always start with an image of the calibration target as a reference for corrections in post.

[jerryph]

Though grey cards are a good tool to have around, I use any of 2 other techniques:

- A simple white paper and take a picture of that. Adjust white balance until it looks pure white. Problem with this and a grey card is that they can be easily lost or misplaced.

- The back of my hand. One time I took a grey card, adjusted it and then took a pic of the back of my hand and compared histograms. My hand is off by a near 1.5 stops. Matter of fact most caucasian hands will be off by 1 to 1.5 stops. I now never again need a grey card and it is a LOT harder to misplace a hand than that card.

Oh, by the way, the card has to fill as much of the frame as it can, the more, the more accurate the adjustment will be if you are using auto WB adjustment. But if you are doing it by eye, enough of the frame so that you can see it clearly. 1/2 the frame or more is good enough.

[pasknucklehead]

thanks guys, will definitely keep those ideas in mind. dc

[Angela2932]

Jerry, could you explain using the back of your hand a little more? If I shoot Raw, how do I adjust the white balance by 1 1/2 stops? Is a stop equal to 1000? (in Camera Raw?)

[jerryph]

Degrees K are colours (from blue to orange... cold to warm tones), and not stop values, which are relative brightness values displayed in the picture. There are 2 issues you need to address and they are exposure and white balance... both can be easily handled using this technique.

Let's say that I am in a badly lit area... a hockey arena for example. They use some ugly sodium vapor lights there and I know that no matter where I go inside that arena, the WB is going to stay more or less the same.

Now, I can shoot in RAW, leave WB in auto and adjust in post process later, or I can take 15-30 seconds and take a few shots to adjust WB and be set for all the rest of my shots in this place.

Basically I look for something white that the lights are shining down on and get close and do a couple of shots adjusting the white balance manually until I see white in my camera LCD screen (the boards of a hockey rink are nice and white, but do not use the ice, there is sometimes a lot of blue in there that you may want to catch!).

I am also pretty good at estimating close by now... I can walk into a room, my bedroom for example, look at the light and know that 2600-2800 are near perfect. I adjust the WB, take a shot, confirm it is very close and leave it there as I shoot for the whole time that I am in the area.

Now if I was in a location like a gym that did not have a white wall for me to test on, I could cheat, pull out a piece of white paper and do what I did above, but since I already see what the colour is, I can get pretty close before testing. Yet to be sure, I still walk out to somewhere into the lights, and take several pictures of my hand (I can usually get WB and exposure down in about 5-10 shots).

I take the shot, look at the colour of my hand on the LCD and histogram location peak, adjust and shoot again until it is really the colour I know my hand is (not too orange or blue). Of course, while there, I adjust the exposure so that you get the right amount of light for the gym (height of histogram peaks) vs the WB location left to right (hand tone for proper WB).

The "trick": When I take a shot of my hand in the lights so that the skin fills most of the frame (focus is not all that important) and look at the histogram, your hand should highlight the histogram at about 1 stop darker than the center of the histogram and if your exposure is correct, the height of the histogram peaks in this area will be near the top without passing it, and of course you can see how well your hand is lit in the LCD picture as well.

That's basically all there is to it... no black magic, no secrets.

Now, understanding how to read a histogram in greater detail can get a little long to write here, so I suggest you google "how to read a histogram" for a little more info. :)

[Angela2932]

Jerry, this is wonderful information! I'm SO printing this out and tucking it one of my books! SO, when you say "adjust the white balance", are you meaning that you go to the white balance setting on the camera and choose one of the options (tungsten, cloudy, etc), or are you meaning you go to "custom" and choose the "pre-measure" (On Nikon D40) setting or the "use this photo" setting? It almost sounds like you're saying there's something where you can dial in the actual numbers (like 2600-2800), but if so, I'm not sure I even know where that IS on my camera!

Sorry if I'm sounding dense; I think I almost have it, but it never occurred to me before to take a picture of my hand, or something white, and then make adjustments. I understand how to use the a white card for custom white balance, and how to use the little eye dropper in Camera Raw in the post processing. But I think you're saying you make an adjustment directly to the camera right after taking the initial photos!