7D and WB calibration with 18% gray card

WickedRay wrote in post #10323266
I don't think I missed this in the thread but a primary reason for using a grey card for white balance is because your everyday "white" papers and card may contain brighteners. These are fluorescent compounds and tend to be quite blue.

Cheers, Ray.

SkipD covered this in the first paragraph of post #6.

SkipD wrote in post #9726411
The problem with trying to use "white paper" as a neutral color reference is that ordinary white paper is not necessarily truly neutral. It is far better to use a product which is guaranteed to be neutral.

A neutral gray card (such as the WhiBal product, for example) is far more versatile than a white neutral reference card. Why? It's because it can be used for both a reference in setting up a "custom white balance" in the camera and it can be used as a reference in the scene. If you put a white card in the scene as a reference, it could be very easily overexposed, blowing out at least one color channel and thus becoming essentially useless.

Since I always shoot in RAW mode when the color of my images is important (which, for me, is all the time), I merely place a WhiBal card (or any other calibrated neutral gray card) into the scene for a test shot. Then, during RAW conversion (a post-processing step), I use an "eyedropper" tool to sample the gray card in the test image. The resulting color temperature and tint numbers are then transferred into the RAW conversion of the rest of the images in the series (in a single batch conversion of the rest).

Do you do this with DPP? If so, can you explain the process with the eyedropper. I'm fairly new using DPP but getting better day by day.

James Emory wrote in post #10324107
Do you do this with DPP? If so, can you explain the process with the eyedropper. I'm fairly new using DPP but getting better day by day.

Open the image in DPP, click on the eyedropper to activate it, then click on your white balance reference, whibal card or whatever and that sets your white balance.Dont forget it only works in RAW

troutfisher wrote in post #10324139
Open the image in DPP, click on the eyedropper to activate it, then click on your white balance reference, whibal card or whatever and that sets your white balance.Dont forget it only works in RAW

Thanks, but what do you then? Do you place the eyedropper on the photo of the grey card then click on it and transfer the eyedropper to a photo and click on it again. I'm confused.

Hendrik C. wrote in post #9861106
Just a quick question about the "select white balance by eyedropper tool"-thing:

Is there any tool to select more than ONE pixel for doing that in the RAW converter of your choice? I'm asking because if you have something like the 50D (I'm currently using one) and you have to deal with medium noise even at lower ISO settings, the chance that you will select a "noisy pixel" instead of a "clear grey pixel" is really high! It would be much better to select something like 30x30 pixel and take the average "white balance value" of them. Any solutions?

Best regards,
Hendrik

Everybody missed the boat on this one. The eyedropper does not select a single pixel whether it is DPP, ACR, or LR. A small area is averaged depending on the image size being viewed at the time. If I am not mistaken, in LR and ACR when viewing at less than 100% the area is 400 screen pixels (not image pixels). At 100% and above, it is 25 image pixels. (or maybe it is the other way around)

Don't worry too much about about being ultra precise since the color of light is not perfectly homogeneous anyway unless you are shooting in a very precisely controlled laboratory environment. When shooting nature and landscape images outdoors on a sunny day there are two strong sources that are quite different in color temperature -- the dominant lighting is direct sunlight which is basically from a point source and then there is the filtered blue sky light which is essentially omnidirectional so all light shadow areas will be illuminated by the open sky lighting. There is also an abundance of lighting that is reflecting off the various environmental features -- green from trees, blue from water, reds and all sorts of colors from rock features such as canyons. The end result is that different parts of the image are being illuminated by light from various sources and that is what gives them interest.

There is a definite downside to trying to white balance lighting in many situations such as nature and landscapes because it will kill the mood that you see before you snap the shutter. For example shooting a rainbow with a dark storm cloud in the background produces a beautiful light that sets the mood of the image. Converting the light to a condition where white is the same as white in daylight will completely kill the image and probably cause the rainbow to disappear. A similar situation exists if trying to WB a sunset. When I am shooting turned wood art objects in the studio, I work very hard to fine tune the WB, but when shooting outdoor scenery and nature images, I try to "romance" the lighting in PP to recreate what I saw in my mind's eye.

If using a gray card for WB make sure that it is not a cheap gray card because the cheap ones are often not neutral. They are intended primarily for exposure so sometimes they are not also satisfactory for WB. Ordinary plain laser copier paper is very good, but do not use ink jet paper because it often has UV optical brighteners which will really screw up WB. I have several different Xrite cards along with WhiBal cards which all work well and produce about the same results as ordinary copier paper.

James Emory wrote in post #10324499
Thanks, but what do you then? Do you place the eyedropper on the photo of the grey card then click on it and transfer the eyedropper to a photo and click on it again. I'm confused.

Sorry I missed that bit. When you have clicked the eyedropper >edit>copy to clipboard. Open the image you want to correct then >edit >paste recipe from clipboard and do that with all the images

Thank you troutfisher, will save/try.

roakey wrote in post #9725367
On page 71 of the 7D instruction manual there’s a description on how to set a custom white balance using a white card. On the next page, it states that an 18% gray card can be used to produce a more accurate WB setting.

What it doesn’t say is how you tell the camera that you’re setting the WB with an 18% gray card versus a white card.

I haven’t been in that part of the camera menu yet, so maybe there’s an obvious way to tell the camera that you’re using a gray card? If not, how does how to set the WB if it doesn’t know what the calibration “target” is?

Roak

You don't, nor do you need to tell the camera. It figures it out on it's own.