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DPChallenge Forums >> Tips, Tricks, and Q&A >> White Balance Question
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10/22/2002 10:32:07 AM · #1
This most recent challenge, and another one elsewhere on shooting white subjects, has prompted me to learn and explore more about the use of white balance for different light sources. I have begun experimenting with custom wb settings.
I have two questions for this group:
1. how many people routinely shoot a reference card, esp indooors?
2. do you shoot a white card or a gray card?
10/22/2002 10:37:20 AM · #2
A reference card for white balance needs to be white. Grey cards will not register your white balance properly. They are used for metering...

I generally use a white card for setting up my balance when working in a controlled environment. It's not foolproof though... sometimes there still need to be some corrections done with software...
10/22/2002 11:01:33 AM · #3
Originally posted by jmsetzler:
A reference card for white balance needs to be white. Grey cards will not register your white balance properly. They are used for metering...




I would have thought so. I asked because I have seen two posts elsewhere where the person preferred grey cards. Didn't make a lot of sense to me, but that's why I asked. Perhaps because PhotoShop lets you select a grey point in levels.
10/22/2002 11:03:33 AM · #4
i do the indoor ref thing all the time. i have to because my artificial light wb settings on my camera invariable yield hideous color casts, whereas the manual setting is really nice and true.

usually i use white coated inkjet paper because im too cheap and lazy to get a real white card ; ) ..

but you can get a kodak card that has reference gray on one side and reference white on the other. i think you can order it from bhphotovideo.com for about 4 bucks.

10/22/2002 11:22:15 AM · #5
A white card is used to set the white balance if your camera allows you
to set a custom white balance. Put the white card into the scene/ under
the light source and set the white balance and off you go.

An 18% grey card is used to get correct exposure under that light source,
as your camera meter assumes the scene it is metering on will be 18%
grey. Typical scenes are not so a grey card can be used to get a correct
exposure setting for the light, which can then be modified to suit the
particular scene (over expose for whiter scenes/ under expose for darker
scenes)

White cards are only of use for digital cameras, grey cards are useful
for both digital and film cameras.

Something I also use quite a bit is a card I have with arrays of complimentary
colours on it. (I.e., blue squares with yellow squares beside them and
that sort of thing - at various saturation levels)

I set my white balance on one of these squares and get a filter with
the effect of the other square. This means for the space outlay of
a 4x6 card, I have the equivalent of 50 colour filters in my bag.

Just another fun thing to do with a digital camera. As an example,
this shot was taken after metering from a yellow tone, to give a
blue tint to the shot. The light and background are actually white :

<img border=0 src="//www.pbase.com/image/6091872/medium.jpg]
10/22/2002 11:51:21 AM · #6
Great tricks, Gordon! I work in printing; I wonder if it would make sense to print up a card with the specific color swatches arranged on it...? Having a color wheel/chart would help pick the right combo...
10/22/2002 12:24:27 PM · #7
When I set white balance I use the grey side of the card.

Equal parts of red, green and blue light make white light, if I use 18% of red light, 18% of green light and 18% of blue light I will get 18% of white light. And I know that the grey side of the card is manufactured to do just that.
10/22/2002 12:43:05 PM · #8
Originally posted by GeneralE:
Great tricks, Gordon! I work in printing; I wonder if it would make sense to print up a card with the specific color swatches arranged on it...? Having a color wheel/chart would help pick the right combo...

I spent 10 minutes in powerpoint and photoshop coming up with this card:

<img border=0 src="//www.pbase.com/image/6208147/medium.jpg]

The full size version can be found here.

This made by varying the saturation across the horizontal access, and
walking around the hue degree angle on the vertical. Free to use for
non-commercial purposes.

To use - simply set your white balance by pointing at one of the
squares, and you should get a filter effect that looks like the
adjacent colour.


* This message has been edited by the author on 10/22/2002 2:52:13 PM.
10/22/2002 12:44:29 PM · #9
Originally posted by daysez:
When I set white balance I use the grey side of the card.

Equal parts of red, green and blue light make white light, if I use 18% of red light, 18% of green light and 18% of blue light I will get 18% of white light. And I know that the grey side of the card is manufactured to do just that.


That's true - I guess I didn't think about it like that. The white
balance isn't looking at the brightness, just the hue and saturation.
10/22/2002 01:16:24 PM · #10
White balancing off a non white card was exactly what I did for thisshot. The light casting the shadows is coming from a projector so it's pretty close to daylight.

re shooting a gray card - as well as the "common" use of metering off a grey card, I believe they are sometimes shot to provide a reference point. Shoot the picture and include a gray card somewhere near the edge (so you can crop it out later) where it gets the same lighting as your subject. In Photoshop "levels" there are 3 eye droppers. The left one allows you to select a pure black point on the picture and balance off that, the right one is for pure white, the middle one is for 18% grey. Click it, then click on the gray card.
10/22/2002 03:26:47 PM · #11
The camera doesn't know whether you are holding an 18% gray card in front of it or a 100% white card in front of it. The white balance setting has nothing to do with exposure it only has to do with the color balance or hue. That's why if you use a yellow card the camera will compensate and remove that much yellow from the image to create a blue hue in your image. I'm pretty sure the camera's white balance meter will meter a gray and a white card equally as long as their color balances are the same. I carry around a light blue card in my camera bag and I can WB meter it when I am shooting a sunset to increase the oranges and reds.

T
10/22/2002 05:29:06 PM · #12
Originally posted by timj351:
The camera doesn't know whether you are holding an 18% gray card in front of it or a 100% white card in front of it. The white balance setting has nothing to do with exposure it only has to do with the color balance or hue. That's why if you use a yellow card the camera will compensate and remove that much yellow from the image to create a blue hue in your image. I'm pretty sure the camera's white balance meter will meter a gray and a white card equally as long as their color balances are the same. I carry around a light blue card in my camera bag and I can WB meter it when I am shooting a sunset to increase the oranges and reds.

T


that's a good use for a warm-up filter. The other commonly used one
is to darken skies for black&white shots. A lot of the better known
Ansel Adam's shots use that for more interesting clouds
10/22/2002 09:00:08 PM · #13
Thanks to all who have posted here.
I've learned quite a bit - and I have a lot of things to try.
04/15/2004 12:19:51 AM · #14
Updated link:

' . substr('//www.pbase.com/image/15668913/small.jpg', strrpos('//www.pbase.com/image/15668913/small.jpg', '/') + 1) . '

Message edited by author 2004-04-15 00:20:05.
04/15/2004 01:03:59 AM · #15
Thanks! Did we set a recond for gap between posts?

Message edited by author 2004-04-15 01:04:35.
04/15/2004 02:40:06 AM · #16
Originally posted by daysez:

When I set white balance I use the grey side of the card.

Equal parts of red, green and blue light make white light, if I use 18% of red light, 18% of green light and 18% of blue light I will get 18% of white light. And I know that the grey side of the card is manufactured to do just that.


Correct, white card and grey card will work equally well for white balance is most circumstances. Only in low light the white card will be more accurate, just because it reflects more.

Another tricks for easy (reasonably accurate) white balance is to put a white disposable coffee cup on your lens, point your camera at the light source and set the white balance. I always carry one in my camera bag.
04/15/2004 05:27:33 AM · #17
I use a chart I found, modifed in CorelPhotopaint, for all colour testing. This chart contains all the primary colours and their complements at full saturation, also with 50% white and 50% grey added. As it is a .png file you can blow it up as big as you like with no degradation and it makes a good check card when printed at A3. Photographed in good light, having first taken a plain white shot to get the colour balance right, it will give you an idea of how your camera performs over a range of colours and saturation!
Unfortunately, I can't upload it to DPC so you can get if from here //62.128.210.205/halweb/pictures/Canon/chart.htm
I have uploaded a .gif version version:' . substr('//images.dpchallenge.com/images_portfolio/8643/thumb/70319.jpg', strrpos('//images.dpchallenge.com/images_portfolio/8643/thumb/70319.jpg', '/') + 1) . '
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