How do you set white balance?

[lunaticitizen]

Here y'are, Leo

https://x3magazine.com/not-all-white...created-equal/

It's quite interesting with a good few illustrations ...

Thanks, Ted. Like Manfred I also am wondering if it's also the same with a Bayer sensor.

[lunaticitizen]

Carefully said, the problem is not so much gray card versus other cards, but rather colour neutrality. Unless the target says it is spectrally neutral it may not be, I have a number of gray targets that are both spectrally neutral and 18% gray (assuming that the card suppliers are being honest). If the supplier is reputable; companies like WhiteBal, DataColor, X-rite, etc. I believe them because that is the business that they are in (and they use stable inks and substrates). An inexpensive card from an unknown source on Amazon, eBay etc, you are taking your chances.

Then why do you think X-Rite has a separate white balance target if their 18% gray balance one is already spectrally neutral? Oh I guess this was just like Dan said, to remove the possibility of white balancing to color noise if the image is underexposed? I guess this hypothesis is easy to verify.

That being said, these solutions may be good enough for the work that you do. Unless you are doing commercial work and are trying to get the exact Pantone colours on a client's logo, close enough is generally good enough. I have known a number of wedding / portrait and event photographers who do shoot JPEG out of necessity. None of the good ones use AWB because the camera will not give them a consistent WB and the images will have a different WB across the shots that they have taken. The ones I have spoken with do one of three things; shoot a present (daylight, for instance), shoot at a constant manually set colour temperature (set the camera to 5600K and use that setting) or do a custom white balance and stick with that unless the lighting really changes. One trick I did learn from a commercial event photographer is that if you use your camera's custom WB function and use the scene you are shooting, the white balance you get is often good enough.

The other question, in my view, is to determine what is good enough. If you look at your camera spec, you will probably find that the range of AWB is more limited than setting a manual WB or using one of the presets, especially at the warmer and cooler ends.

Finally, if there is a "white", "black" or "gray" area in your image, you can often pull off a decent WB from them in post. A car tire is usually black, street signs are often white (as are paint lines on a road) or wedding dresses, concrete or asphalt are often fairly neutral. It may not satisfy everyone, but are often good enough for a starting point.

Those approaches sound very reasonable. Thank you.

[xpatUSA]

It seems that the Sigma software is set up slightly differently than how the Bayer sensor based software does this. I don't know if this is necessary or that someone went out of their way to make things more complicated than necessary.

Straw Man alert! ...

The Sigma/Foveon raw-to-RGB conversion is made necessary by the panchromatic response of the three doped silicon layers.

I know that Sigma uses Bayer sensors in some of their cameras. Is this approach used for those sensors as well, or is this something necessary for Foveon sensors?

I do not know how WB is handled in the two Sony-sensored "fp" series cameras. The article I linked to predates those two models by a good few years.

At the end of the day, both types of cameras deal with red, green and blue data. The de-mosaicing step is not necessary for the Foveon based cameras, so why the additional complication of having to choose the type of WB?

"Red, green and blue data" does not tell the whole story. The two types of camera sensors have significantly different spectral responses.

Sigma/Foveon, of necessity, does it right. For my SD9, the panchromatic raw data is firstly converted to XYZ D55 color space - not RGB - with a 3x3 matrix. Next, a separate 3x3 matrix WB correction still in XYZ space is applied. Then, and only then, is an XYZ to RGB transform applied.

The SD9 only outputs raw files, so all of the above is done in Sigma's SPP conversion software.

http://kronometric.org/phot/sensor/f...len%20Rush.pdf

See figure 3 and figure 4 for the difference between the Foveon and the Bayer sensor responses.

The process outlined in the article bears a strong resemblance to what I went through in the colour "wet" darkroom when making subtractive process colour prints. The film type (daylight or tungsten) was determined [to be] the starting point and making minor tweaks in the printing process with single or pairs of yellow, magenta and cyan filters is how colour corrections were made.

OK.

[rpcrowe]

I own several different sized WhiBal cards since Donald originally told me about them. They are expensive for what you get, however I have been using the first card I purchased for around ten years and it is still going strong. Pro rating the price of that card over that long period results in what is IMO a negligible cost.

OTOH: unless absolute color accuracy is needed, some of the less expensive color balance cards available on eBay might do the job fairly well...

After-all, if a black car tire or the white stripe on the road (or in my case the white coat of many of my dogs) will suffice to get you marginally close to the correct white balance, a cheap WB card should do the same. Better than nothing especially when shooting RAW.

I really like wearing a WhiBal or other WB card on a lanyard around my neck when doing portrait shots. It is very easy to hand to the subject to hold or place in the scene with a dog (I haven't been able to teach my dogs to hold the card - YET) and having the card on a lanyard ensures me that I will have it available...

[xpatUSA]

Thanks, Ted. Like Manfred I also am wondering if it's also the same with a Bayer sensor.

Only one way to find out, I guess, Leo.

Assuming that one's camera has WB presets and that one can use a color-picker for color-balancing in post.

[DanK]

Only one way to find out, I guess, Leo.

Assuming that one's camera has WB presets and that one can use a color-picker for color-balancing in post.

I think Manfred's question was specifically about Sigma cameras with Bayer sensors.

I think the answer in the case of most cameras with Bayer sensors is clear: if you are shooting raw, the preset has no impact whatever on the color data in the file, and it doesn't alter the effects of balancing with a spectrally neutral part of the image. It just adds metadata. Does anyone have information suggesting that this is not correct?

If one is shooting JPEG, all bets are off because a very large amount of data are lost in the initial conversion to JPEG, and that conversion is determined in part by the present.

Leo, I find this thread a little puzzling. If you want really fine-tuned control over color, I think would help a lot more to shoot raw than to shoot JPEG and then worry about the differences between white-balance tools.

[xpatUSA]

Originally Posted by xpatUSA Only one way to find out, I guess, Leo.

Assuming that one's camera has WB presets and that one can use a color-picker for color-balancing in post.

I think Manfred's question was specifically about Sigma cameras with Bayer sensors.

If that is intended as a rebuttal, I find it quite difficult to imagine that Sigma's handling of the Sony sensors is significantly different to that of any other Bayer CFA-equipped camera.

[DanK]

Not a rebuttal. I know nothing about Sigmas use of those sensors. But afaik, the WB setting on my cameras has no effect on the results of using a neutral area for WB. Then again, even though I have read and heard this countless times, it may not be true. I could test it, I suppose.


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[xpatUSA]

Not a rebuttal.

Glad to hear it, Dan.

I know nothing about Sigmas use of those sensors. But afaik, the WB setting on my cameras has no effect on the results of using a neutral area for WB. Then again, even though I have read and heard this countless times, it may not be true. I could test it, I suppose.

I too could shoot my G9 at my colorChecker card but that would raise the specter of lighting and the resistance of this Forum to numbers and graphs outside of the realm of the Real World ...

[lunaticitizen]

Leo, I find this thread a little puzzling. If you want really fine-tuned control over color, I think would help a lot more to shoot raw than to shoot JPEG and then worry about the differences between white-balance tools.

Dan, my original motivation was to test the dedicated WB sensor of my camera. The preliminary result is that it's good enough for my living room. I've yet to try it outdoor. But even if the conclusion is that the WB sensor is not accurate enough, I don't have any real interest in using proper custom WB as a part of my workflow.

Ultimately, I want to understand how cameras do automatic white balancing. I've read some textbooks and papers but there is a lot of math required and I haven't really done any advanced math in a professional setting; I'll need (a lot of) time to understand them.

Here is an example of the paper.
Lam, E. Y. and Fung, G. S. K. 2008, Automatic White Balancing in Digital Photography, <https://courses.cs.washington.edu/co...iteBalance.pdf>

[xpatUSA]

I too could shoot my G9 at my colorChecker card but that would raise the specter of lighting. etc.

Well I did anyway and learned a good lesson**



** the lesson being "if shooting JPEGs, get as close as you can in-camera to the scene WB!".

The WB's were Shade, Daylight, AWB, Tungsten. The lighting is a cheap warm white LED strip.

Each pane above was color-balanced in RawTherapee on patch #22 Mid-Gray. Each patch #20 Almost White was measured as a*,b*:

Shade: 20.6, -47.8
Daylight: 13.9, -41.5
AWB: 2.6, -10.3
Tungsten: 0.3, -14.3

Those familiar with the CIELAB space will know that those numbers should be 0,0, same as was patch #22.

I have to say that I didn't expect such bad results!

[DanK]

Or another lesson: don't shoot JPEG.

Re an earlier part of this thread--whether the in-camera settings matter with raw--I did a simple test. As I thought, it doesn't matter.

I shot a print of a test image, along with a whiBal (bottom left) in the same lighting--natural light indoors, with no direct sunshine--with the camera set first for 2500 K and then for 6000K. I then balanced both simply by clicking on the whiBal card in Lightroom. Pardon the blur--this was a very slow shutter speed, and I should have attached a remote shutter release. However, since color is the issue, not sharpness, I won't bother redoing them.

Original, shot at 2500K:




Original, shot at 6000K:




Balanced, 2500K:




Balanced, 6000K:



To be fair, in real life, it's not one click, as one doesn't want the whiBal in the final image. In Lightroom, it entails one click to balance the photo with the neutral card, one or more clicks to select the images to sync, and a couple of clicks to sync the white balance. I haven't timed it, but it's just a few seconds. A great deal less time than fussing with custom white balances, and it works, all the time.

[Manfred M]

Dan - your experience echos mine, but that being said, I virtually always shoot JPEG + raw because images I post to social media are often SOOC (sRGB JPEG), so the white balance needs to be "good enough". The raw files goes into the "serious photography" folder where I process the best images for posting here, printing, etc.

That means that there have been times, in tricky lighting, where I have gone for a custom white balance. Most of the time, I stick with one of the presets, because that gives me a consistent look across the range of images (JPEGs).

Everyone has different needs.

[xpatUSA]

Everyone has different needs.

True!

Today, the last thing I needed was a perfect color balance:

Lightning Struck Cedar:


I'm not into clearing brush just for a picture, sooo ....

... I cranked up the red channel, down with the green channel, et voila:


The shattered tree stands out a bit mo' better ...

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