any difference between white card and neutral grey card for white balance?

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Bryanpic114

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Hi everyone,

What is the difference between a white card and neutral grey card for setting the white balance? Thanks
 
There's a slight danger in taking a WB reading from a white card in that if you over expose [or even correctly] you may blow a channel or two in the white area. Your camera or Raw converter tries to balance the RGB values in this area, but if there's actually more red, for instance, than the camera could measure, then the correction will be wrong. Better therefore to measure from a neutral midtone, i.e. grey.
 
Deckard said:
There's a slight danger in taking a WB reading from a white card in that if you over expose [or even correctly] you may blow a channel or two in the white area. Your camera or Raw converter tries to balance the RGB values in this area, but if there's actually more red, for instance, than the camera could measure, then the correction will be wrong. Better therefore to measure from a neutral midtone, i.e. grey.
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What do you mean by channel?

And so its better to ALWAYS set the white balance with a grey card? Thanks for the help.
 
Digital files are made of light in red green and blue (RGB) and these are referred to as channels.
 
Bryanpic114 said:
So where is the "white" area in those channels?
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White is an equal mixture of all three channels. As is a neutral grey and also pure black. When sampling colours in Photoshop the value of each of the three channels will range from 0 to 255 (if working in 8 bit). Values of 0,0,0 will be black, and 255,255,255 will be white. Various shades of grey will be somewhere between.

That's what makes using a grey card so useful. By comparing the amount of red green and blue present, it's possible to see if there is too much/not enough of any of the three colours, and to make adjustments so that all three colours are equal, giving a neutral image with no colour cast, irrespective of the light source being used.
 
Scarecrow said:
White is an equal mixture of all three channels. As is a neutral grey and also pure black. When sampling colours in Photoshop the value of each of the three channels will range from 0 to 255 (if working in 8 bit). Values of 0,0,0 will be black, and 255,255,255 will be white. Various shades of grey will be somewhere between.

That's what makes using a grey card so useful. By comparing the amount of red green and blue present, it's possible to see if there is too much/not enough of any of the three colours, and to make adjustments so that all three colours are equal, giving a neutral image with no colour cast, irrespective of the light source being used.
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Good post. :thumbs:
 
Scarecrow said:
White is an equal mixture of all three channels. As is a neutral grey and also pure black. When sampling colours in Photoshop the value of each of the three channels will range from 0 to 255 (if working in 8 bit). Values of 0,0,0 will be black, and 255,255,255 will be white. Various shades of grey will be somewhere between.

That's what makes using a grey card so useful. By comparing the amount of red green and blue present, it's possible to see if there is too much/not enough of any of the three colours, and to make adjustments so that all three colours are equal, giving a neutral image with no colour cast, irrespective of the light source being used.
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Ok so if I'm understanding correctly, gray will "middle" out all the colors in an image, while balancing white will be on one end of the spectrum, and while black is on the other end of the spectrum. Correct?

And if grey cards are so popular for white balancing, why is it that "white" cards are still being sold and used and even sold together with grey cards?
 
But.........................

Nikons and Canon differ slightly so I have read and have found out myself that for Canon use a white card and Nikon use a grey card, much better skin tones for portraits. It might be different for landscapes. This is my opinion but a theory shared by lots of others.
 
tiler65 said:
But.........................

Nikons and Canon differ slightly so I have read and have found out myself that for Canon use a white card and Nikon use a grey card, much better skin tones for portraits. It might be different for landscapes. This is my opinion but a theory shared by lots of others.
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What is the "difference" that makes a nikon use a grey card and canon use a white card?

Now I'm confused because a moment ago I was told to use a gray card. Now I'm being told to use a white card (I shoot canon).
 
I disagree with Tom, for the reasons already outlined. Canon or Nikon, Sony or anything else, if you clip one of the channels you will get an inaccurate white balance. Now this is a risk, and for fear of confusing you further, you can use white, but only as long as you ensure it is relatively underexposed.

As you're not certain, stick with a grey target, I believe it's the best choice anyway. There are several validated types such as WhiBal cards and varying lens caps, I use a Digital Grey Kard I got inexpensively from Amazon.
 
Or just get a Lastolite Xpobalance and not worry about it. :)
 
It doesn't matter whether you use a grey card or a white card, so long as they are both spectrally neutral and exposed to middle grey or thereabouts. So, point camera at card (grey or white), set exposure to zero EC or zero on the meter for a manual exposure, take a shot and set your white balance.

Think about it - underexposed white is grey. Overexposed grey is white. Meter either at 0 and you'll get the same result.
 
tdodd said:
It doesn't matter whether you use a grey card or a white card, so long as they are both spectrally neutral and exposed to middle grey or thereabouts. So, point camera at card (grey or white), set exposure to zero EC or zero on the meter for a manual exposure, take a shot and set your white balance.

Think about it - underexposed white is grey. Overexposed grey is white. Meter either at 0 and you'll get the same result.
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Well said Tim :thumbs:

It makes no difference what tone it is, so long as it's neutral. Personally I prefer white as it's easier to tell if white is neutral just by looking at it, plus you can busk it by taking a reading off a white table cloth, or back of an envelope, piece of paper or whatever and you'll always be very close, if not perfect.

On the other hand, not all 18% grey cards are actually neutral grey, if you get a couple side by side and compare. Not many of them are exactly 18% grey either, but that's another topic ;)
 
MisterE said:
The interiors of Lowepro bags are a good approximation to 18% grey.
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Unfortunately that's an internet myth. And Lowepro have never claimed it. It's neither 18% (my Lowepro is 0.6 stops lighter, leading to under exposure) nor neutral grey.

If you're stuck, it's better than nothing though ;)
 
HoppyUK said:
Unfortunately that's an internet myth. And Lowepro have never claimed it. It's neither 18% (my Lowepro is 0.6 stops lighter, leading to under exposure) nor neutral grey.

If you're stuck, it's better than nothing though ;)
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You're partially right. That's what approximation means! :p :D

I have five Lowepro bags, and three of them have a slightly darker shade than the other two. The lighter shade is a very close match to a fold-up cloth type 18% reflector thing that Amateur Photographer gave away a while ago. They give the same exposure readings. The darker one has a one stop difference. So it depends which bag you have.

There has been some unresolved internet discussion over the recent years that 18% is a bit of a myth itself anyway. It's not my intention to divert this thread off topic so I shall leave it with just this one link and say no more

http://www.bythom.com/graycards.htm
 
On the other hand, not all 18% grey cards are actually neutral grey, if you get a couple side by side and compare. Not many of them are exactly 18% grey either, but that's another topic
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There are two very different types of grey card knocking about these days. There are the old ones from the jurassic era that were made for exposure metering. These don't need to have equal values accross the red, green and blue channels because such things were not important to film. Then there are the modern colour balance cards, which need to be equal over the RGB ranges but don't need to be an 18% grey for exposure.

All a bit of a head mess.
 
MisterE said:
You're partially right. That's what approximation means! :p :D

I have five Lowepro bags, and three of them have a slightly darker shade than the other two. The lighter shade is a very close match to a fold-up cloth type 18% reflector thing that Amateur Photographer gave away a while ago. They give the same exposure readings. The darker one has a one stop difference. So it depends which bag you have.

There has been some unresolved internet discussion over the recent years that 18% is a bit of a myth itself anyway. It's not my intention to divert this thread off topic so I shall leave it with just this one link and say no more

http://www.bythom.com/graycards.htm
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Haha okay! ;)

The 18% grey thing isn't a myth. That's a universally accepted standard and everybody still references, even if it it originally related to film.

The debate is whether manufacturers actually calibrate digital cameras to 18% grey, and I think there is plenty of evidence to suggest that they don't, even though they never specify this. I think it's tied up with ISO, which seems to be a bit of a moveable feast, and which of course is very marketing-sensitive hence the secrecy.

dazzajl said:
There are two very different types of grey card knocking about these days. There are the old ones from the jurassic era that were made for exposure metering. These don't need to have equal values accross the red, green and blue channels because such things were not important to film. Then there are the modern colour balance cards, which need to be equal over the RGB ranges but don't need to be an 18% grey for exposure.

All a bit of a head mess.
Click to expand...

Fair comment :)

Which kind of suggests, if in doubt, set the white balance from white.
 
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Again, Lastolite Xpobalance. Colour neutral, and black/white/18% on one side, 18%/+1 stop/-1 stop on the other. :)

They're about 30-35 quid (they had 'em as low as £26 at Focus), and worth every penny.
 
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