Using a Gray card to get the w/b for tricky lighting...

[magomago]

Hi all -

I'm actually quite confused over which one to do. I had an experience where I had very odd lighting (a very low low light room where I needed to bounce flash off...but all the walls and ceilings were yellow) and am having trouble correcting it.

so I got interested in using a card for a custom white balance. apparantly white cards are trickier to use as overexposure can easily happen, so the proper choice is a gray card which yields more accurate results. After reading and googling so much I've noticed there are actually MANY different kinds...and I'm not sure which one to use (heck, there are even color checkers!).

18% is the most common one that appears- but I read that this is actually a mistake and that it is for printing....and that 12% should be used. But then numbers like 13% appear randomly.

I'm sure that in reality 12 to 13% probably makes absolutely no perceptible difference. 18% maybe make a minor difference, but doesn't matter in most cases.

But i'm still interested in what is technically the "proper" card to take a w/b reading off of.

 

[magomago]

http://photo.net/bboard/q-and-a-fetch-msg?msg_id=000hry

I think I finally found the answer....so 13% it is

 

[nero2]

magomago, I think you are a bit confused on the subject. Are you talking about white balance or exposure? A gray card's primary use is to meter off of, that's why having a lighter or darker card makes a difference. For WB, as long as the surface you are trying to set the WB is neutral, it doesn't make any difference its value. Keep in mind that for WB purposes, not all gray cards (%18 or not) are actually neutral.

Here are some links on the subject of gray cards, hope they help:
http://en.wikipedia.org/wiki/Gray_card
http://www.betterlight.com/pdf...aper/wp_gray_cards.pdf

 

[magomago]

I know where you think I'm stuck up....but I'm interested in w/b. From the wiki link it states

In addition to providing a means for measuring exposure, a gray card provides a reference for white balance

which is exactly what I want it for....most of the time when its a single light that is clearly defined I won't use it...but in those complex lighting situations, or a situation where I can't nail the color temperature on my own I want to simply adjust the w/b using this In a situation where I can simply snap a pic of the center of the card and then apply it on an as needed basis it makes my life much easier~

btw i'll check out that article later today and post once more~

 

[nero2]

the second link has some reviews of gray cards for WB purposes. Also, check these guys out:

http://usa.gretagmacbethstore....i%20Gray%20Balance.htm
http://www.rawworkflow.com/products/whibal/index.html

there is also the expo-disc:
http://www.expoimaging.net/

 

[Gooberlx2]

18% is the number I remember from my photo classes, but yeah, that's for exposure. I bought a nat'l geographic field manual a long time ago when I first got into the hobby (back in 96 I think). Had an 18% grey cloth included....kinda cool.

ahhh nostalgia. I break out my passed down Pentax Spotmatic sometimes, still works well too. My Elan II was also a great camera. Some day I'll have enough to go for a 30D (or maybe 40D) and get my thumb wheel back.