Being wrong on a graycard

I recently replied to a post called, "Do you use a gray card only for high contrast scenes?" Located here....
http://forums.dpreview.com/forums/read.asp?forum=1002&message=31221806

The answer I gave was very incorrect.

I tried replying to that post to admit my error, but no matter how many times I tried to do so, it would not let me. So now I have resorted to making my error even more known by formulating a free standing post to call even more attention to myself.

While I am a bit surprised that I have been shooting for this long and did not know this, I admit to being wrong. And for a very long time apparently. While I hate to admit being wrong, because a bruised ego can smart for a very long time, I really need to admit I am.

A long time ago, a photographer took me under his wings as I was learning the ropes. This is where I got the knowledge. That a gray card was used for getting a white balance. He never elobarated further, and I never knew enough to ask, or to doubt his word.

I have been using the same gray card for I don't know how many years, to white balance the camera before the wedding ceremony and the reception. (It works better than a simple white piece of paper, by the way.) And I have never used it for anything else. I have never read anything on a gray card, so I have never been corrected on this error. I had no reason to read anything, as I thought I understood.

I have been corrected now. Thankfully, I have not passed that information along to others, or I would feel like cr@p about now. But before I -do- turn out any information in the form of tutorials, I always check my facts anyways.

But I have to tell you, this is quite embarrassing. I stand here before all the senior members of this forum and apologize for giving very wrong information. I assure you, there was no doubt in my mind that I was correct in this, or I would have not said one word.

To the OP of thatoriginal post, I promise you that I don't make it a practice to spout off without fact checking first. I just KNEW I was correct and had no reason to doubt the information that was passed on to me years ago. My sincere apologies.

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Are you quite certain that a grey card works better for white balance than an ultrawhite piece of paper? I have camera manuals that recommend either one. I have tried both and can't tell any difference. The main issue is the surface used to calibrate the white balance must not contain any color components other than pure white and black.

I can only speak from experience on the 5 DSLR cameras I have owned. Yes. White does fine. An 18 percent gray card works better. The manual does say both. And both work. The gray card seems to produce a better choice out of the two. But try it yourself and you make the call.
--
Free stuff for the beginners. No charge. Really. Of
course donations are accepted... KIDDING!

http://freephotographytutorials.blogspot.com/

I suppose this little gap in knowledge could fall into the category of an "unknown unknown". Something that you didn't know you didn't know.

At least you have a positive attitude towards learning, which is admirable.

Regards,
Peter

Cedarhill said:

Are you quite certain that a grey card works better for white balance
than an ultrawhite piece of paper? I have camera manuals that
recommend either one. I have tried both and can't tell any
difference. The main issue is the surface used to calibrate the white
balance must not contain any color components other than pure white
and black.

Click to expand...

It may depend on how it is used. If the card (either white or grey) fills the entire frame, the camera will adjust exposure accordingly and the result should be identical.

If however, the card is placed some distance away, within a larger scene, and a spot WB measurement is made, the white card may be overexposed very near to clipping and at this extreme, the results may be incorrect.

Even something as simple as a piece of paper requires some skill to operate successfully.

Regards,
Peter

The only way I have ever done white balance is to fill the entire field of view.

I was going to correct your statement first, but seen it was you. I didn't post a disagreement because you had me thinking I could be wrong, even though I knew I was right.....at least 96% sure. If it came from you, then what the heck have I been thinking?

I use a grey card, actually a grey/white/black target. This way I have multiple choices. I have my model hold the target and I make sure she is also in the frame. This way, when I do my WB adjustments, I have her skin tone to view as a reference as well as the colors of her outfit.

Personally, I find seeing the model helps A LOT in setting WB.

--

The greatest of mankind's criminals are those who delude themselves into thinking they have done 'the right thing.'

• Rayna Butler

Happens to all of us, being caught out. We could be champs alone, but in this world of the internet, there are so diverse levels of knowledge, skill and questions could be both in depth and naive at the same time.

BCJames said:

I have been using the same gray card for I don't know how many years,
to white balance the camera before the wedding ceremony and the
reception. (It works better than a simple white piece of paper, by
the way.) And I have never used it for anything else. I have never
read anything on a gray card, so I have never been corrected on this
error. I had no reason to read anything, as I thought I understood.

Click to expand...

I have a "classic" grey card, made by Kodak I think. It has two sides, 18% grey 9or should we call it 12% - again some with a prodigious sense of history and accuracy will tell) and the other side is white. Was white just the "back" of the card or was white a genuine effort to provide white?

I am pretty sure that the grey was for reflective meter reference point, and eventually since each serious photographer would have it in his kit, that because a reference point for white balance. Remember, in the days of film, we couldn't just twiddle the white balance - the film was already loaded as daylight or tungsten balanced film. And we could not do a Live View or Review check on the spot.

But the white side of the card? And whether if everything were to start again, you could use white or grey or black as a reference point for electronic WB.....?

--



Ananda
http://anandasim.blogspot.com/

i think you gave the correct answer to use gray for white balance purpose.
http://whibalhost.com/_Tutorials/WhiBal/01/
http://www.rawworkflow.com/whibal/

but gray is also used for exposure meter as different purpose too. gray has two different purposes.
1). white balance

2). in old time, use the sekonic exposure meter to measure the gray paper when people wear black or white dress. cuz film camera was confused to measure person's white dress will go underexposure (face look too dark) or person's black dress will go overexposure (face will look pale).

--
cuong aka buzz
--
carl zeiss lenses do matter to me.

GodSpeaks said:

I use a grey card, actually a grey/white/black target. This way I
have multiple choices. I have my model hold the target and I make
sure she is also in the frame. This way, when I do my WB
adjustments, I have her skin tone to view as a reference as well as
the colors of her outfit.

Personally, I find seeing the model helps A LOT in setting WB.

Click to expand...

I can think of two separate ways of using a neutral target such as the grey card to set the white balance.

One method is to take the shots in RAW mode and the adjust the WB in post processing. I suspect that is what is being described above. A grey target is preferable in this case, as a white one could be over-exposed and be unreliable. In this case, the reference shot thus taken needs to be saved and used later when processing a batch of photos.

The other way to set WB is to use the camera's Custom or Manual adjustment of WB which is useful in shooting either JPEG or RAW images. In this case the white/grey card should be the only thing in the frame during the adjustment. The camera may also have an option as to whether to read the entire frame or the centre spot when adjusting the WB. In this case, though the shutter button is pressed, no actual photograph is saved, the WB value is simply stored in the camera and used for subsequent shots.

Of course, it would be possible to use both the above methods, one does not exclude the other.

Regards,
Peter

Cedarhill said:

Are you quite certain that a grey card works better for white balance
than an ultrawhite piece of paper?

Click to expand...

"Ultrawhite" paper typically contains optical brighteners that make the light reflected by the paper bluer than the ambient light. Additionally, if any of the color channels is saturated then you can't get useful white balance information off the white surface.

sherwoodpete said:

The other way to set WB is to use the camera's Custom or Manual
adjustment of WB which is useful in shooting either JPEG or RAW
images. In this case the white/grey card should be the only thing in
the frame during the adjustment. The camera may also have an option
as to whether to read the entire frame or the centre spot when
adjusting the WB. In this case, though the shutter button is pressed,
no actual photograph is saved, the WB value is simply stored in the
camera and used for subsequent shots.

Click to expand...

The Canon 450D manual states to use spot metering and to ensure that the spot frame is filled with a white subject. A photo is then taken and when setting Custom WB you tell it to use that photo. I've delete protected the photo for indoors in my house.

This thread has now somewhat confused me as to whether a grey card would give a better result and also how to know what is white.

AnthonyL said:

sherwoodpete said:

The other way to set WB is to use the camera's Custom or Manual
adjustment of WB which is useful in shooting either JPEG or RAW
images. In this case the white/grey card should be the only thing in
the frame during the adjustment. The camera may also have an option
as to whether to read the entire frame or the centre spot when
adjusting the WB. In this case, though the shutter button is pressed,
no actual photograph is saved, the WB value is simply stored in the
camera and used for subsequent shots.

Click to expand...

The Canon 450D manual states to use spot metering and to ensure that
the spot frame is filled with a white subject. A photo is then taken
and when setting Custom WB you tell it to use that photo. I've
delete protected the photo for indoors in my house.

This thread has now somewhat confused me as to whether a grey card
would give a better result and also how to know what is white.

Click to expand...

Unfortunately that's a camera I'm not familiar with. However, it is the nature of spot metering, that whatever is placed with the spot meter zone will be metered and exposed as if it were 18% grey. In that sense, there is really no difference between white and grey (or even black, as long as there is sufficient light available).

In this case, there should be no problem with individual colour channels saturating or clipping through over-exposure, as the spot metering should reduce the exposure of a white target accordingly.

The other issue is that raised by markkuk, of some whites being different to others. Some paper is whitened by the use of optical brightening agents. These function by absorbing invisible ultraviolet light and emitting visible blue light (somewhat similar to fluorescent green, pink, orange and yellow which can look unusually intense). Such ultra-white paper may not be the most suitable target.
Regards,
Peter

Ananda,

Thanks for making reference to the 12% issue! Few people know about that. Our Kodak and traditional gray cards do have a true 18% reflectance, but our nice expensive handheld and in camera meters (most of them anyway, are SHOCKING** - calibrated to 12.5%! I recall that the official Kodak gray card says we should compensate (open up) by a half stop. I always wondered why my incident readings were always a half stop different than my gray card readings and scratched my head for a long time until I read that fun little factoid.

Another thing, people typically just memorize the 18% number for middle gray. I believe it scales proportionally to exposure. Thus:

2.25% is the darkest with the least (almost non visible) detail (Zone 2)
4.5% is very dark with some usable detail (Zone 3 -2 stops from middle gray)
9% is dark gray (Zone 4 -1 stop from middle gray)
18% is middle gray (Zone 5)
36% is light gray (Zone 6 +1 stop from middle gray)
72% is white with some usable detail (Zone 7 +2 stops from middle gray)
144% is white with the least (almost non visible) detail (Zone 8)

So to shift the tonal portion of a scene that our meter tells us is middle gray to make it appear as light gray for example (in tone, not color - when we shoot in color or course), we need to open up how much? With film I believe we'd say open up one full stop, right? But with digital, I think we need to open up just 1/2 stop.

Why is this? I think the zone system was devised for film and is unlike digital with its linear behavior. That 1/2 stop difference can become significant to digital when using a meter to measure an 18% gray card and not factoring in the 1/2 stop adjustment when we decide to use the zone system as a reference to shift tones - especially on the high and low end of the scale.

So do I have this right or did I mess up anywhere in the analysis?

Regards,
Mike

--

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AnthonyL said:

The Canon 450D manual states to use spot metering and to ensure that
the spot frame is filled with a white subject. A photo is then taken
and when setting Custom WB you tell it to use that photo. I've
delete protected the photo for indoors in my house.

Click to expand...

The color balance in your house will vary depending on the light coming in from the windows. If you're really particular, you should recheck it when you shoot.

I'm the OP of that gray card question. Thanks for clarifying and starting another discussion. I was admittedly confused after your reply but have learned more about using gray cards from both threads.

Greg Nut said:

The color balance in your house will vary depending on the light
coming in from the windows. If you're really particular, you should
recheck it when you shoot.

Click to expand...

Thanks. I meant at night with the lights on but point taken.