White balance three card trick

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Ken Gofton

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Ken
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I've just bought an Opteka Digital Grey Card, and in fact it comes as 3 cards - grey, white and black. While I believe the grey card is the one I should normally use for pre-set white balance, in what circumstances would the white or black be more appropriate?
 
Good question! Any of the three could be used for setting white balance, but a grey card can also be used for setting exposure.

So if you don't have a grey card you could use a white card to set the white balance, but if you do have a grey card then I can't see why you would ever want to use anything else.

Hopefully somebody else will be along shortly to enlighten us.
 
Many thanks to both of you! Can I add a supplementary? My camera's manual says I should fill the viewfinder with the card to set the white balance. However, the camera is new and for now I only have a fairly wide angle lens with it, and the cards are quite small. I find that if I get close enough to fill the viewfinder, I'm shutting out a lot of light and, I imagine, distorting the reading. Should I ignore that instruction, and just get the card in the centre of the viewfinder? Alternatively, I have a decent sized piece of white cardboard - should I use that instead?
 
When I use a grey card I take a test shot with it in the picture close to the point of interest. I can then pick out the grey card during PP and adjust the WB if required that way. Re: filling the viewfinder, I think as long as you cover the area that the camera is checking for the exposure you should be fine. Have a play around and see which works best for you.
 
The immediate task I have on hand is to photograph an artist's paintings for reproduction in a magazine. It's a task I've had to do before - different camera, different artists - so I'm conscious of the need to get the right balance correct. I'll take your advice and try some test shots this afternoon...
 
Just be wary of fluorescent lighting - I've had problems with big shot to shot white balance shifts.
Initially I thought is was the Auto WB on the camera, but choosing a WB manually and applying to the whole set just made the problem worse.
I also had problem shooting art-work on a gorgeous day with fluffy white clouds; the light coming in the window dramatically changed the colour temperature in an unpredictable way.

I'd recommend a grey card next to the image so you can check and correct as needed.
Putting white and black cards in the shot would also make sense so (as already pointed out), so you can check the white and black points on the histogram; there's nothing an artist will hate more than their dark moody painting appearing brighter than intended (or vice-versa).
 
Ken Gofton said:
The immediate task I have on hand is to photograph an artist's paintings for reproduction in a magazine. It's a task I've had to do before - different camera, different artists - so I'm conscious of the need to get the right balance correct. I'll take your advice and try some test shots this afternoon...
Click to expand...

The usual recommendation for white balance is a white card (less chance of noise skewing the reading) though grey is also fine. It's got to be neutral white though, or neutral grey (equal quantities of red, blue and green) and the fact that your Opteka also has black and white suggests it may be more of an exposure reference card and therefore not exactly neutral. They often aren't. Try a sheet of white paper.

If colour accuracy is important, then the best method is to include a reference in the actual picture (eg X-Rite Colour Checker) and correct it in post-processing.
 
Shoot RAW and place your white or grey card beside the painting and include it in the image. If the image is not your camera's aspect ratio you'll want to crop off a bit anyway, so you can put it there. Then you can set the white balance off the card when processing. Be careful that the painting is evenly lit, and that there are no strongly coloured reflections nearby. I once shot a painting under a nice white sky standing on an easel on a lawn, anf got a green tinge from the lawn strongest at the bottom of the painting. Not something you'd ever see with your eyes when on the spot bcause your eyes have such good auto WB.

Anotther way of doing it would be to put a clean polystyrene cup over the camera lens, hold the camera by the painitng pointing back at the camera shooting position, and set white balance from that -- the incident light falling on camera.

Use more than one method. It's so annoying when you realise hours later back at the computer that you did something wrong :)
 
Ken Gofton said:
The immediate task I have on hand is to photograph an artist's paintings for reproduction in a magazine.
Click to expand...

For a task like this, where getting the correct colour is vital, I wouldn't stop at using a grey card for WB. I'd get a ColorChecker Passport and shoot that alongside the painting, then use that to produce an accurate profile in LightRoom.
 
Many thanks to everyone for your input on this query, with some really interesting and helpful answers. I'm intrigued by the use of a polystyrene cup, but I might well invest in a ColourChecker Passport, too.
 
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