Why Auto White Balance isn't

[Inkanyezi]

The myth of Automatic White balance, AWB
With the digital camera came the ability to set white balance, something that in the past was managed in the laboratory when printing, after the photographer, hopefully, had chosen the right type of film for the lighting and, also hopefully, also had corrected any deviance by filtration.

Now there is a little problem when the camera is told to automatically set white balance. There are several possibilities, none of which is certain to give a correct result. Purportedly, the camera shall set White Balance to the light source. However the optical element that takes in light is directed at the scene and will not see the light source. There is no way it can assess the light source; hence it is bound to rely on guesswork.

One of the methods that is implemented in the firmware in many cameras, is to analyse the scene and set white balance by tweaking RGB channels. The problem with this approach is that it does not relate to the lighting of the subject, but the light reflected from the subject. When using this method, there will be a magenta cast in mainly green subjects and a blue cast in mainly yellow ones etc.

So another approach, also used by camera manufacturers is to choose between the fixed settings in the camera, where there's sunlight. cloudy, open shade, incandescent, flash and fluorescent to choose from. Hopefully the camera may hit the right one and the image may come out with correct white balance.

Which one of all possible methods that the camera manufacturer has implemented is hidden to the user.

I'll illustrate with a few images, taken with a simple compact camera at Auto, so all the pictures are a bit under-exposed, due to mainly rather bright subject, but nevertheless, they illustrate the concept. The lighting in all cases is diffuse light from an overcast sky through the window.

First an image taken in my kitchen, where the walls are yellow. The image has a blue cas due to AWB:

Then an image taken in my room, which has blue walls, which render a yellow cast due to AWB:

Then again in the kitchen, but now with white balance set to sunlight:

And lastly, my blue room but white balance set to sunlight:

There are of course other algorithms than those used by this camera, and this one also offers another approach, also automatic, so you won't know which one it will choose. When the light is strong, it uses daylight setting when set to AWB. It is however evident that the camera will not know what's in front of it, and any guess might be wrong. Setting to one of the presets is likely to give a more consistent and better result than AWB.

[Mike Buckley]

Setting to one of the presets is likely to give a more consistent and better result than AWB.

I think that depends on the camera, at least when considering my typical shooting situations using my three cameras. I agree with your statement when using my oldest camera model though not so when using either of my later models, which are two and three generations later. The accuracy of the Auto White Balance in those later models is clearly far superior to that capability on the earlier model, so much so that I rarely use a preset configuration on the later models.

[DanK]

Here's what I think are the two morals of this story:

1. The big one: The automation built into a camera can sometimes help one get the settings you want, but it is not a reliable substitute for knowing what those settings should be, because the computer is just blindly following an algorithm.

2. The specific one: shoot raw, and one can stop worrying about white balance, as long as you have a reference object in at least one shot.

[AB26]

The true moral of the story:

Learn how to use your cameras preset WB.

Thanks Urban.

[Inkanyezi]

I think that depends on the camera, /.../

I think you might be missing the point, which is in the subject line. Automatic White Balance, AWB, may be a more complex algorithm than the one used in older cameras, but new ones also share the fundamental flaw. There is no way for the camera to assess the light source. All algorithms used for setting white balance automatically are based on guesswork.

A better alternative than a preset is to set the white balance with a reference, but the preset will be more consistent than AWB, and we know nothing about how AWB is programmed and what guesses it is based upon at any given time.

[Mike Buckley]

I think you might be missing the point

No, I'm not missing the point of your subject line, which is certainly valid. Instead, I'm offering the reason that I agree or disagree with the concluding statement in your first post, depending on the situation.

[Manfred M]

In the limited context you are writing about Urban, I agree with what you are saying; but given that it represents a small subset of real world shooting, I can’t get particularly concerned about it. This is very similar to reporting how reflective light meters give the wrong readings for certain non-average lighting conditions; true, but so what. There are ways of dealing with these situations.

I find AWB usually does a half-decent job in many daylight situations, other than at times close to sunrise and sunset. Add artificial lighting to the mix and things can get a bit more challenging.

Take this issue indoors where one usually encounters a mixed lighting situation, and the readings can be quite odd indeed. The problem with artificial light sources is that they are so variable. Tungsten light changes colour temperature as it ages, the filament will get hotter as the tungsten gets thinner. Fluorescent tubes are even worse, as there are so many different colour temperatures straight out of the box. Different lamp manufacturers use different phosphors, and again output changes as the tubes age. Here, making the right choices as to where to shoot can be much more important that trying to figure out the theoretically correct colour balance (because it may not exist at that particular location).

The problem with a reference object in a shot is that it only gives a good reading for the lighting conditions it is taken under. If one is sloppy and we get the wrong reading, the colour balance will be garbage, whether we shoot RAW or not. It is not always possible to get a reference shot that meets these conditions, and even then, colour balance has a lot to do with compositional / artistic choices, rather than getting the colour to be “correct”. As an example, I will colour balance portraits to be a bit warmer than what a test shot shows to be “correct”.

[Glenn NK]

Here's what I think are the two morals of this story:

1. The big one: The automation built into a camera can sometimes help one get the settings you want, but it is not a reliable substitute for knowing what those settings should be, because the computer is just blindly following an algorithm.

2. The specific one: shoot raw, and one can stop worrying about white balance, as long as you have a reference object in at least one shot.

Dan - agreed.

To which I might add: adjust the WB in PP to achieve the desired look.

A major advantage of digital over film is that it's far easier to adjust WB, and to use different WB settings to change the effect/mood of the image. Don't get caught up in reality - it rarely if ever exists.

Glenn

PS: just read Manfred's post - good points.

[rpcrowe]

I have no problems with AWB...

1. I will shoot with auto white balance and use a WhiBal reference card in my frame and adjust the color balance in Camera Raw using this reference point...

2. Often, I cannot/will not use the WhiBal card but, this is usually in daylight, travel situations. The AWB of my modern Canon DSLR cameras does a fine job in adjusting the white balance in most general daylight situations but, occasionally I will tweak that to get a result more pleasing to my eye. If I were doing product photography in which totally accurate, dead-on, color balance was required, I might very well do things differently.

3. When I am shooting portraits of my white Maltese dogs, I will frequently dispense with the WhiBal target and use the dog's white coat as my target. After all, I want the dogs coat to be white...

I have recently been working with the NIK software package, since it has been reduced in price as a result of acquisition by Google. The White Neutralizer Filter of NIK Color Effex Pro 4 does a very creditable job of getting color casts out of white Maltese Coats and, of course, white wedding dresses...

I can also use the Custom White Balance option but, seldom take the time or effort to do this...

[Inkanyezi]

Of course it could be argued that "it is a small subset" where AWB won't "do a decent job".

I think most of the arguments miss the point, even though they confirm the statements.

I already declared that there are several approaches, and I illustrated one of the methods that is fundamentally flawed. When the camera tries to set the scene to neutral, it will be severely off when there is a dominant colour. The lighting was not a problem here, and sunlight white balance would set it almost right. What I illustrated with the kitchen wall was that the camera cannot, and will not, assess the light source. If it reads anything at all, it will be from the scene, and frequently such a reading will be in error. That is not a small subset, but it is most of the images we take, somewhere in the ballpark of 100%.

I also stated that there are other approaches. Digital system cameras that I have tried mostly set white balance to daylight when it is set to Auto. Reading responses here, I conclude that "in most daylight situations it does a decent job" would mean that in most daylight situations, daylight white balance is the way to go. "Decent job" here indicates that it does no job at all. And there's where we are again at a full circle reasoning. We're back at the subject line. Automatic white balance, AWB, is not! It is an oxymoron, because the only time it "does a decent job" is when it does no job at all. Then photomag editors complain that the AWB doesn't work well in tungsten lighting.

I might be picky, but if there is a setting on my camera, I would like it to have a function, and I would also like it to have a function that I can understand. Now, I can of course say as someone else, that I don't have any problem with AWB, because I don't use it. It is true, I don't have a problem. But there are scores of people out there that do have a problem. Why don't the colours come out OK when the camera is set to AWB? Why would every camera review state that AWB is so-so, when in fact it cannot ever be or even become a functional feature of the camera? It is more as "everyone else has an AWB setting, so we must include it", whether it makes sense or not.

Of course RAW might be The Right Thing, but then why set the camera to AWB when any of the fixed settings would do? Wouldn't daylight setting work for all conditions when we shoot RAW? At least, it would be consistent. In the past, we had two different films, daylight and tungsten. It should be enough these days too. Cameras even have a flash setting, but I haven't yet seen one, not a single one, that sets a decent white balance with its own built-in strobe or any of the dedicated hotshoe ones. It works fine with studio flash, but not with the built-in ones or the manufacturer's dedicated strobes. Every single one I have tried renders a bluish cast.

I think we should not disregard the fact that the vast majority of casual shooters don't use RAW, and they rely on their camera's automatic features. Most of them pop up the flash when lighting is low or when they are indoors. Some don't even know how to turn off the automatic flash. Even many serious amateurs would prefer bypassing the RAW conversion by letting the camera do it for them, provided it does a decent job. Most cameras do. The feature that does not "do a decent job" is precisely the automatic white balance. Just as when we shot Kodachrome, it is OK in most daylight conditions and off when the riding gets rough.

My more exact point is that, as AWB in fact isn't, the setting should not be there. There should not be an "automatic white balance", as there is no such animal in the zoo.

[RustBeltRaw]

Purportedly, the camera shall set White Balance to the light source. However the optical element that takes in light is directed at the scene and will not see the light source. There is no way it can assess the light source; hence it is bound to rely on guesswork.

Try taking a photo of a subject against a luminous, colored background sometime. I did a candid portrait against a wall of green LEDs once, and his skin was furiously magenta. Even having the light source in the shot is no guarantee of anything. The camera simply looks at the scene's brightest part and calls that white, regardless of its true color. In cases where the scene's brightness is very uniform (such as your walls), the system will also struggle. However, it works just fine in bright, consistent light. Like any tool, it's great for some jobs, but you need to know when to put it down and grab another one. After dark, indoors, or near intense colored lights, I'm always on some kind of manual balance.

[xpatUSA]

Try taking a photo of a subject against a luminous, colored background sometime. I did a candid portrait against a wall of green LEDs once, and his skin was furiously magenta. Even having the light source in the shot is no guarantee of anything.

Quite so. Equally frustrating is when the subject itself is a light source. Some time back, I was taking what watch guys call "lume shots" but with the express purpose of determining the luminance of the glow-in-the-dark stuff. Much correspondence with the well-respected Doug Kerr followed but I don't recall that we ever satisfactorily resolved the question of the correct WB setting for such a shot.

[William W]

I think we should not disregard the fact that the vast majority of casual shooters don't use RAW, and they rely on their camera's automatic features. Most of them pop up the flash when lighting is low or when they are indoors. Some don't even know how to turn off the automatic flash. Even many serious amateurs would prefer bypassing the RAW conversion by letting the camera do it for them, provided it does a decent job. Most cameras do. The feature that does not "do a decent job" is precisely the automatic white balance. Just as when we shot Kodachrome, it is OK in most daylight conditions and off when the riding gets rough.

Well, assuming that the statistics above are correct: that’s all the more reason for HAVING some Automatic Function as an option for all that “vast majority” of people to use. At least that “vast majority” will then get a reasonable result, rather than them having to set the White Balance or Colour Temperature manually.

- OR -

Perhaps we could have cameras set to 5500K (or whatever)?

It could be reasonably argued that the eyes of that “vast majority” won’t discern the various subtle colour casts, anyway.

My more exact point is that, as AWB in fact isn't, the setting should not be there. There should not be an "automatic white balance", as there is no such animal in the zoo

AND - back to the "Subject Line":

”Why Auto White Balance isn't”

Well, it is “automatic”.
But we seem to all agree that doesn’t always “White Balance” correctly.

So the “Automatic” part of the label – “is” correct.
But the “White Balance” part of the label – “isn’t” correct.

So it seems to me the concern is very simple and is all about a labelling issue which is misleading and possibly terribly confusing, but only confusing to a minority of folk who shoot raw, use AWB and then use Colour Temperature correction in Post Production .

This can be remedied quite easily.

If the function were to be kept, then just relabel it “Automatic”: and that would be a more suitable label for the “vast majority of casual shooters don't use RAW" . . . and they could then continue to rely on their camera's (all be they limited and not perfect) automatic features.

For the remainder, the minority, who do shoot raw and correct the WB in Post Production - well, I don't think they'll have much trouble adjusting to the name change.


WW

[Inkanyezi]

Bill, I think you're sniffing at the core of what I see as a problem there. Marketing blurb and esoteric terms, that confuse more than they explain. We have through most times I can remember had a lot of confusion with technolingo that is inadequate, as the present usage of "analogue" for silver salt based photographic processes that were with us for over a century before electronic sensors took over.

I am in fact deeply disturbed by marketroid lingo, which is often misleading. Canon lied to us when they introduced HTP with the EOS 40D, and I won't trust a liar a second time. It was a lie, a blatant lie, there was no such function. I am regarding the "AWB" much in the same way, and it is disturbing, because all players share the disinformative lingo.

When electronic cameras first came to the consumer market, with colour, they invariably were analogue, recording the images on magnetic tape in lines, just as the television tubes did. The CCD sensor was read sequentially and the analogue levels recorded on the magnetic tape. They were not digital, they were analogue, and they used electronic sensors with Bayer pattern. They had a white balance button, and were provided with a white balance lens cap. There was no sunshine setting, no tungsten setting, but white balance was a routine of pointing the camera to the light source with the white cap on and pressing the white balance button, that would balance the output to the tape, so that the recording would show up on the video screen in correct colours.

White balancing did not arrive with digital cameras, but with analogue cameras. White balancing was a routine back then, a very simple routine. Put the white lens cap on, direct it toward the light source, press the WB button, then take off the cap and shoot.

So it is more a semantic issue than a phototechnical one. It disturbs me, that there is a pseudofeature in my camera. If it could be deleted from the menu system, to me it would be a Good Thing. Indeed a normal setting to daylight would be more consistent than AWB that does something - whatever. AWB, just as HTP are just TLA:s with no substance. It clutters the menu of the camera, because there are choices that are useless. In that way it makes life a bit more complicated than if it could be eliminated. Of course I don't have a problem with the "function", as I don't use it. I am just disturbed by its actual existence. There is a menu item cluttering up my screen when I open up the white balance section, a menu item that is useless and should not be there. I would prefer to be able to customise the WB section to the three or four items that I really use, instead of having four or five more that I won't ever use. Too many options, and particularly utterly unusable ones, is not a help to me when I use the camera. So the "problem" actually is that the menu item is there, and that inadvertently it is possible to use it.

No camera manufacrurer will tell you what it does. But it does not set white balance at any time, ever. So far, I haven't seen one that can properly identify tungsten light and set WB accordingly. It does not work any better than daylight slide film would. My "standard" setting is rather "Sunny" than AWB, and therefore I don't use "iAuto", which falls back on the AWB setting as well as everything else automagic. I have learned to live with it, but it is in a way a bit as a pebble in the shoe that you want to get rid of.

[William W]

Well: If I might state modestly that I think I have more than ‘sniffed at the core’ at what is disturbing to you.

I’ll add that, I believe you are in for being disturbed for a long time and in many, many more ways, if you seek the solution to be only the purist and correct use of words, in any marketing, sales or generic description of a process or object, which is for general and public consumption.

WW

[AB26]

Hi Urban,

I think this thread is very relevant and important to those whom wish to improve their skill in “Painting with Light”.

The WB and other camera settings is a never ending debate. I have come to realise there are a few distinct groups within the photographic ensemble. I would like to emphasise that the views of all need to be respected as none can be either right nor wrong due to the very nature of the trade.

The first group is by far the majority. Those whom bought a camera to do very basic image capturing. This is a group using phone cameras and P&S cameras never using any other setting but Auto.

Then there is a group whom bought a DSLR just because they can and they want to look like “photographers”. This group of camera owners also never shoot in any other mode but Auto.

Getting to the more serious amateurs you find a group whom believe that learning how to use functions of the camera is the only source of creating good photographs. This group of photographers will only shoot Jpg and is often referred to as purists.

Another group would be those whom use basic camera settings and believe the computer is more important in creating good photographs. This group only shoot in RAW and then spend hours manipulating images in Photoshop.

Yet another group would be those whom believe both camera and computer have flaws and both have to be used to create good images. This group shoot both Jpg and RAW and believe that mastering settings offered in camera is more important than manipulating images in computer software.

And then there are the Photographers.

The more advanced you get in “The Art of Painting with Light” the more you realise the importance of getting it right in camera. The more you wish to get it right in camera the more you ask questions about settings offered by the tools you are using. The more you learn how to use the tools of your trade the more you use Manual settings. The more you master Manual settings in camera the more creative you can get. Many of the setting are aids in assisting prospective photographers to learn the trade and turn it into an art.

As Bill said: Why not have Auto functions on cameras to offer the vast majority of users the opportunity to be able to get decent results from whatever they do with the camera?

The Auto WB setting is there for those of us whom do not yet understand Kelvin temperature fully and mastered the art of capturing the light.

[pnodrog]

Please define getting it right in camera. Ready for printing or something else?

Urban is correct of course AWB is a myth - It is AWB approximation based on the light reflected from the the scene. In the good old days automatic colour negative printing machines compared the overall colour value of the negative and adjust the RGB printing times to make it conform to a calibrated average (sort of a muddy green). If a white cat was taken sitting on a red blanket then in the resulting print the cat would have a strong cyan cast. It was referred to as subject failure and in the better labs all prints were inspected and when such a fault was spotted the print would be redone with a colour correction applied.

AWB is trying to perform an similar sort of trick and can only make an approximate correction based on a scene conforming to a average range of colours and the camera doing a most likely correction. No doubt some algorithms will try and search for neutral tones in the scene or use scene recognition software to make the assessment. At the best the camera can only make a reasonably educated guess but it is a long long way from fool proof.

[Mike Buckley]

Then there is a group whom bought a DSLR just because they can and they want to look like “photographers”.

I've been trying that for a decade and it has never worked for me.

[revi]

Quite so. Equally frustrating is when the subject itself is a light source. Some time back, I was taking what watch guys call "lume shots" but with the express purpose of determining the luminance of the glow-in-the-dark stuff. Much correspondence with the well-respected Doug Kerr followed but I don't recall that we ever satisfactorily resolved the question of the correct WB setting for such a shot.

That you couldn't reach a correct white balance isn't surprising: there isn't one.
By that I mean, that due to the nature of the light source, you cannot assign a colour temperature to the light.
Colour temperature is defined as the temperature (in K) of a black body emitting light of the same spectral composition as the light in your photo. Such sources have a
continuous spectrum with now sharp peaks.
That works reasonably well for sunlight and incandescent lamps, it fails for fluorescent and phosphorescent light sources. The latter show a spectrum with peaks and holes
(i.e. certain colours are very intense, others are absent).
And the glow-in-the-dark stuff is phosphorescent, and has a discontinuous spectrum. So there is no 'correct' white balance setting, the best you can hope for is getting
close to the visual impression on both the glow stuff and the rest of the watch (not guaranteed at all!).

[xpatUSA]

. . .

Perhaps we could have cameras set to 5500K (or whatever)?

It could be reasonably argued that the eyes of that “vast majority” won’t discern the various subtle colour casts, anyway.

I can attest to that. My brother visited recently and brought his Panasonic point&shoot along. He qualifies as a member of the 'vast majority'. The 2GB card was crammed with 5MB max quality jpegs. On uploading a few to the computer, the blue cast, to me, was glaringly obvious. He himself did not see it until I found one with a neutral color and corrected the color cast. Flipping back and forth betwixt the two made the difference obvious, even to his 'vast majority' eye.

Turned out that, somehow, the WB had gotten set to 'incandescent' and had been left there. I reset it to AWB. The explanation as to why that would be better (for him) did not got smoothly but the image made the point quite clearly. We also found that an image with no neutral colors shot in shade with the WB set at 'incandescent' was almost impossible to correct in PSE6.