Grey Cards

[Richard Lundberg]

Every **** time I google something I run into opinions, controversy, and craziness. I thought I'd better get a decent grey card for Christmas from one of my kids, so there you go. There's a nice selection and price range, I think I want 4x6 white grey black. But I ran into this thing that the original grey card by Kodak was 12 or 13 percent instead of 18.
So, what should it be really, and what is the RGB equivalent of 12%. Is 18 percent wrong, for *** sake?
I've been using the white balance tool in ACR with pretty good results but ordinary white objects in scenes are all over the place and usually there's no reliable grey. I got very good results on a jpg shot of a woman by using the black tool on the sole of her shoe, but that too is unusual.

[Manfred M]

Grey, white, 12% - 18% it really doesn't matter. What does matter is that that card is neutral and you can pull of a neutral colour balance from using it. People all have their opinions and their favourite brands; I happen to use ones made by Lastolite (mostly for video work) and X-rite for photography.

[Richard Lundberg]

I see your point. Why use different brands for video and photo?

[Inkanyezi]

Just to confirm that our preferences vary: I mostly use a piece from a milk container for white balancing, although I also have a WhiBal card.

The purpose is not to find out exposure, but white balancing, and the degree of reflectance is not crucial, but the milk container cutout is about 85 % and I think WhiBal is about 70 %. The reason for using high reflectance is that it supplies more data on which to calculate white balance.

Reasons for one or the other: My WhiBal is the key-ring size, about an inch by two, and it is too small for setting white balance in the camera for jpegs straight out of the camera. The piece of plastic from the container is larger and covers the measurement area in the camera. When shooting RAW, the WhiBal can be used. I haven't bothered to get a larger WhiBal, as the milk container plastic renders a balance that I find pleasing.

[Manfred M]

I see your point. Why use different brands for video and photo?

White balancing a video camera is somewhat akin to doing a custom white balance for shooting jpeg; it is something done in camera. This means you need a large enough target to cover the entire FoV of the camera / lens combination. The Lastolite "card" I use a folding device, similar to folding reflectors that collapse into a small space. This means it is portable and easy to use on location.

For colour, when I shoot RAW, all I need is a neutral sample in the image, so I use the X-rite Color Checker Passport. There are a number of advantages here as when I shoot the whole card, rather than just the grey target, I can do a custom colour profile of the setup using the X-rite software. As well, the target allows me to pick specific targets if I want to bias the shot to the cool or warm side.

[Richard Lundberg]

That makes sense, hadn't thought about video since I trashed my big RCA camera ten years ago.

You're right about the big white object, too, Inkanyezi. I would like a white that's white though. When I worked for an aircraft company the commercial side had orders for airliners in 91 shades of white. We eventually worked it down to 20. Later on, when I was in charge of bids and proposals for an electronics outfit, customers who were all government agencies had placed orders for rack mounted equipment in 14 shades of grey with various blues and greens in the mix. I remember what a fight it was to cut that down.

[Colin Southern]

It depends on what the purpose is; white-balancing, exposure, or both.

For exposure, 12.5% is technically correct. For white balancing, spectrally neutral is the primary property, but after that, the more reflective it is, the better the result (bigger numbers give more accuracy) (so long is it's not so bright it ends up clipping a channel in the exposure). Personally, I use a WhiBal card for white balancing (available in various sizes), and a color checker passport for making colour profiles (necessary if you're serious about accurate colour, but I don't know how many converters that that particular product works with (it's designed primarily for ACR).

[NorthernFocus]

IMO unless you're doing commercial work it's a waste of time. I've abandoned using white/grey cards because every time I do, I'm not satisfied with the results. The thing is, our eyes/brains don't see true colors in nature. They see the color of light being reflected. So if the light falling on the object is warm or cool, then we see a warmer/cooler color. Granted to some degree our brains do compensate, but there is a reason we all seek the magic "golden hour" of sunrise/sunset to shoot in. Use your WB card to correct a sunrise/sunset shot and it will not reflect reality at all.

I've reverted completely to "correcting" color purely to my own mental image of what the scene looked like at the time or at least my memory thereof.

Sorry for blathering on when I didn't really have an answer to your straightforward question. But this is a topic I've been thinking a lot about recently. And I just KNEW you would be interested in my opinion on the topic

[Colin Southern]

IMO unless you're doing commercial work it's a waste of time. I've abandoned using white/grey cards because every time I do, I'm not satisfied with the results. The thing is, our eyes/brains don't see true colors in nature. They see the color of light being reflected. So if the light falling on the object is warm or cool, then we see a warmer/cooler color. Granted to some degree our brains do compensate, but there is a reason we all seek the magic "golden hour" of sunrise/sunset to shoot in. Use your WB card to correct a sunrise/sunset shot and it will not reflect reality at all.

I've reverted completely to "correcting" color purely to my own mental image of what the scene looked like at the time or at least my memory thereof.

Sorry for blathering on when I didn't really have an answer to your straightforward question. But this is a topic I've been thinking a lot about recently. And I just KNEW you would be interested in my opinion on the topic

It really depends on what you're doing more than whether it's commercial or not.

Golden hour landscapes are a great example - one would never want a technically correct white balance for one of those - it's visually correct white balancing all the way for that, but at other times it's really helpful for getting memory colours correct (especially skin tones).

White balancing to a gray card doesn't mean your stuck with the result - it just gives a technically accurate and consistent starting point - 'tog can go warmer or cooler from there (and eliminate tint if using artificial light sources).

[Inkanyezi]

As Colin states, brighter is better for balancing, as long as you don't approach clipping.

Of course it is possible to get also a 12.5 % reflectance card to zone VII or VIII by plus-compensation, but a more reflective target will give you sufficient data when you expose the scene normally. Hence the target is included in one shot in the series, to get the starting point for balancing the whole set. If using a less reflective card, a grey card intended for exposure, there will be less data for the software to calculate white balance.

[Black Pearl]

I just use the inside of my LowePro bag which is a neutral (enough) grey and I have it to hand without carrying anything else.

[DanK]

The starting point is Colin's point: do you want it for exposure or white balance? The 18% is for exposure and, AFAIK, came from the tone curve of some films. As Colin pointed out, it is not correct for digital anyway. The % (where on the tonal range from white to black it falls) is not relevant to white balance, so if that is your concern, you can forget about it. The manufacturers of the whiBal cards are explicit that theirs are designed to be spectrally neutral and not to provide exposure guidance.

I too carry a whiBal (the smallest, which fits in my pocket and which I can hang around my neck during a shoot if I want). I find it invaluable. Often I don't need it, but when I want a reference as a starting point for postprocessing, I take one shot with the whiBal under the appropriate light. It is then literally only a couple of seconds to have ACR or Lightroom adjust for that, and a few more seconds allows you to copy the white balance to every image in the folder. Of course, there is no reason to be dogmatic about that particular color temperature. for example, I find that flowers are often more pleasing when warmed up a bit. However, having true neutral as a starting point is very handy, and using a neutral card is as easy as using anything else (and much easier than some other options).

For exposure, I simply don't find it worth carrying anything. If exposure is tricky, I use spot metering and meter off something the tonality of which I think I know.

[Colin Southern]

The 18% is for exposure and, AFAIK, came from the tone curve of some films. As Colin pointed out, it is not correct for digital anyway.

I haven't worked the maths, but I'm told that the difference between 12.5% and 18% is only 1/3 of a stop anyway.

[Inkanyezi]

Not much maths, if you just think of the ISO number series: 100 - 125 - 160 - 200 - 250 - 320 - 400
So it's slightly more than 1/3, more like ½ f-stop.

[Richard Lundberg]

I don't think you can trust "found" whites in a scene to be spectrally neutral. In one recent image the temperature varied by several hundred degrees when using the balance tool on four different white objects. I doubt that a piece of a plastic milk container is, probably contains blue.
Interesting discussion though. Certainly grey balance is just for starters.

[Glenn NK]

IMO unless you're doing commercial work it's a waste of time. I've abandoned using white/grey cards because every time I do, I'm not satisfied with the results. The thing is, our eyes/brains don't see true colors in nature. They see the color of light being reflected. So if the light falling on the object is warm or cool, then we see a warmer/cooler color. Granted to some degree our brains do compensate, but there is a reason we all seek the magic "golden hour" of sunrise/sunset to shoot in. Use your WB card to correct a sunrise/sunset shot and it will not reflect reality at all.

I've reverted completely to "correcting" color purely to my own mental image of what the scene looked like at the time or at least my memory thereof.

Sorry for blathering on when I didn't really have an answer to your straightforward question. But this is a topic I've been thinking a lot about recently. And I just KNEW you would be interested in my opinion on the topic

Well Dan, now there are two of us - that gave up on WB targets/cards/milk bottles.

I really like that idea by Urban - if it doesn't work out, no monetary loss - but a plastic milk bottle would look strange in someone's Christmas stocking.

Glenn

[Colin Southern]

I don't think you can trust "found" whites in a scene to be spectrally neutral. In one recent image the temperature varied by several hundred degrees when using the balance tool on four different white objects. I doubt that a piece of a plastic milk container is, probably contains blue.
Interesting discussion though. Certainly grey balance is just for starters.

Whilst it's true that the quality of "found whites" (or more correctly "found spectrally neutral objects"), often it's either a case of "use what you can find" or "nothing at all". It's always a bonus when someone has included a reference, but often I get images from others for correction and printing that don't contain such a luxury.

Some people are excellent at nulling colour casts by eye, but I'm not so good -- so usually there's something in the scene (concrete, writing, paper etc) that gets it closer than I can (as a starting point anyway).

It's the "B" solution, but it's still better than only the "C" solution.

[chauncey]

The percentages that you'll mention...do they correlate with the eyedropper in LR?

[terrib]

I just use the inside of my LowePro bag which is a neutral (enough) grey and I have it to hand without carrying anything else.

What a great idea! Thanks for that.

[Colin Southern]

The percentages that you'll mention...do they correlate with the eyedropper in LR?

Not sure if you're meaning me or not. If so, sorry, can't say as I don't use LR (can't stand it to be honest).