Let's Have a Real Conversation about White Balance
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Hi folks,
Yes it’s been a while since I wrote anything. Full time work is what pays for the ability to do this kind of stuff and I am incredibly grateful at how busy it has kept me for the last six months. With good luck, it will only get more busy.
This time I want to have a frank conversation about white balance. This is clearly an area of concern and misunderstanding based on the regular influx of questions here, at the camera club and on the Community forum over at KelbyOne where I am a moderator. Let’s dive in.
What is White Balance, Really?
When it comes to work as image creators, whether for stills or video, white balancing can take the form of a noun or a verb. Let’s start with the verb usage as it conveys the message very clearly. The process of setting white balance or white balancing an image or clip exists to remove a colour cast, with the intent to render the image as if shot under a light with a colour temperature of approximately 5500 degrees Kelvin, aka daylight. This very popular choice is still a completely arbitrary one that the artist can make or not make. Why?
Because there is no such thing as “correct” white balance.
I accept that such a statement flies in the face of many web articles, opinions and software mcmarketing. I am ok with that because regardless of what the adherents may say, there is no such thing as “correct” white balance.
As in many aspects of art, there are preferences. My dear friend, the superb instructor and photographer Scott Kelby, very often teaches his flash students to use an orange gel on their flashes to warm up skin tones. Whether he chooses a ⅛ CTO, ¼ CTO or any other gel is a personal preference. There are folks who absolutely strangle their nether regions because what he is doing, is not “correct”. Such statements are wrong, because his choice is correct for him. He is the artist and can do whatever he wants and the rest of the world’s opinion is not relevant unless he was judging his own values and work based on the commentary of others. He does not, which I find immensely commendable. By the same token, I find myself using gels on lights often, not for “correctness” but to help tell the story that I want to tell.
Thus white balance is a preference, an opinion, and a choice that a creative makes in order to achieve an artistic goal.
Why a Grey Card?
The purpose of including a grey card in an image is two-fold and these outcomes can be bound together or completely separate based solely on the decision of the artist involved. A grey card provides a neutral reflectance reference. This means that in light that is consistently 5500 degrees Kelvin and has no changes in luminosity across the face of the card will return under perfect conditions RGB valuations pretty close to 127 for each of the red, green and blue channels.
I have encountered some folks who near apoplexy when their grey card RGB measurements are not all exactly equal. Considering the very low cost of grey cards in general and the variety of sources for them, it would be immensely surprising if they were all, or any, were perfect. Inks, dyes, and paints all change over time. This is why the Spydercolor Color Checker has an indicator to tell you when the device’s accuracy has really moved past acceptable. Your $4 grey card does not. I have seen grey cards used as plate holders, backgrounds, drink coasters, writing bases and numerous other activities which could impact the accuracy of their reflectance.
The second use of the grey card is as a reflected light source for a reflected light meter. By filling the frame entirely with a grey card, your in camera meter, or external spot meter will be reading an entity that by design is as close to middle grey as is reasonably possible. Since all reflected light meters work on the basis of using math to provide exposure readings that would render middle grey as middle grey, this is a useful, although not necessarily required metering tool. Use of one when the reflected light from the subject will not mathematically mean to middle grey is a huge advantage. Consider a snow field or a bride in a white dress as examples of this situation. This use has nothing to do with white balance and is all about getting an accurate exposure reading for that specific scene. Of course the grey card must be lit by exactly the same light as the subject, or the meter reading has a high probability of being inaccurate.
From a white balance perspective, a grey card is a guide tool to help you get to neutrality. They are not exact and expecting them to be would be self-deluding.
The White Balance Eyedropper
The purpose of this tool is to allow the user to click on a portion of the image that is natively middle grey for stills or perfectly white for video. This reading allows for neutralization of colour casts to achieve a whit balance that is very close to what would be in place if the light source was a consistent and unchanging 5500 degrees Kelvin.
It is important to note that this tool comes free and is hardly exacting. The greater the variance of the reflected colour temperature from the goal of daylight, the greater the error bars would be on the graph showing the adjustment needed. It is not a rule, it’s a guide. Those thinking that the use of an eyedropper tool will always provide a perfect white balance for 5500K with all RGB values equal are wrong. Moreover, the RGB values shown by some tools will be based on the precorrection data, not the post correction data. It’s also important to note that the greatest accuracy will occur when the reflectance is around RGB values of 127. White balance in video uses a completely different scale called IRE and that scale is measured differently from camera to camera. In this case, use your eyedropper tool on a pure white card which should give RGB values near 255 for each colour to achieve neutralization as best possible.
JPEG or Compressed Video vs RAW Files
I ask patience from those readers who are starting to find this a broken record. Imagine how I feel having to repeat myself so often.
A RAW file whether for stills or video has NO encoded colour balance. The file may have an encoded JPEG still as a thumbnail for stills, or a low res subframe in RAW video. These are things that we see when we view these files without a proper RAW converter. Judging an image or clip for colour based on these embedded entities is foolish and has as much chance of misguiding you as not. Every week I read another note from someone furious that the preview images don’t look like the RAWs when they open them up for editing. This is how things are supposed to be, not an error. Whether a user likes this fact or not is immaterial of the fact. Previews are only previews and the best course of action is to assume that they are vague approximations at best.
It is also believed that a JPEG image, or a compressed video file cannot be colour adjusted. This is not true of course, but it is critical to understand that a huge amount of data is discarded before recording happens and you cannot make something from nothing, software mcmarketing BS notwithstanding. You can adjust the white balance just not as much as with RAW files and not with maker defined presets as found in tools like Adobe Lightroom. I personally wish that Adobe would drop their estimations of the maker’s in camera white balance settings as it would reduce substantially the amount of user confusion when they are working with JPEGs.
From this section, you should conclude that white balance settings in the camera mean ZIP ZERO NADA to the actual RAW files. Your post processing software may use the WB hints that are encoded in the metadata in the RAW file that reference the in camera settings, but these are hints only and make no actual difference to the RAW file at all. This specific topic appears counterintuitive to many and lots of folks struggle to get past this point.
If colour fidelity is important to you and you are shooting in JPEG or compressed video, you have already build the rod for your own back and may wish to consider shooting in RAW only.
The Impact of Digital Noise
The greater amount of digital noise in an image or clip, the harder it is going to be to make accurate white adjustments. Noise typically comes in two flavours. There is luminance noise, often erroneously referred to as grain, and colour noise where zoomed in sections are made up of an assortment of different coloured dots.
Luminance noise will screw up meter settings off a reference target because of the amount of luminance variance that occurs because of the luminance noise.
Colour noise will make a mess of using an eyedropper tool because your middle grey or pure white target is not either but is instead a blob of coloured dots.
For accuracy your target must be sufficiently lit and your ISO level low enough so as to not make noise a factor.
Choosing a Non-Neutral Target
As we know, the idea of using a target is based on that target being completely neutral. However, there are folks who have been misled to believe that software knows what should be neutral by some form of AI or magic. This is not so. Clicking your eyedropper tool on a target that is not neutral will give you an adjustment for certain, but the probability that it is what you were expecting is a number rapidly approaching zero.
Mixed Sources
Mixed source lighting is a nightmare to balance specifically because the different originating sources have different native colour temperatures. Expecting auto white balance to get this right falls very much under wishful thinking and that AWB does as good a job as it does is amazing. The best resolution is to choose a colour balance that favours your dominant source and let the other source be what it is. In post production, you can use filters and masks to bring these areas into closer alignment, but accept up front that you are making a lot of work for yourself. This is why cinema lighting professionals colour meter each light and then gel the group so they are all producing the same colour temperature.
Colour Metering
Your cameras do not have built in colour meters. Colour meters work with incident light not reflected light, so while cameras do have white balance settings, these are highly arbitrary and if you are shooting in RAW as you should be, completely immaterial.
If you are shooting something where the subject coloration must be perfect and exactly match a specific swatch colour, such as the red used by Coca Cola for example, then your workflow is going to be different. In this case, you must be in complete control of the light, colour meter each source, and then correct it either with gels at source or with corrective filters in post to get the colours exact.
If you are in need of a professional colour meter, these are not inexpensive devices. I used the old Minolta Color Meter III in professional capacity for many years and the current market leader is the Sekonic C-800 Learning to use a colour meter is a process as well, it’s not quite as simple as just turn it on and go. If you want to purchase one, please do so through this link to B&H Photo Video. You get the same great price and service and you support my site.
Conclusions
I don’t expect that this article solves all questions pertaining to the subject but I do hope that it answers a lot of the common ones and helps to dispel some myths and misinformation.
Do you have an idea for an article, tutorial, video or podcast? Do you have an imaging question unrelated to this article? Send me an email directly at ross@thephotovideoguy.ca or post in the comments. When you email your questions on any imaging topic, I will try to respond within a day.
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I'm Ross Chevalier, thanks for reading, watching and listening and until next time, peace.
