White Balance, Part II

I Think He's Compensating For Something

In part I, we barely talked about white balance. I was too busy laying the groundwork for that discussion by describing why you need white balance. To recap, it's because the perceived color of a thing is profoundly affected by the light that falls on the thing. While our eyes compensate for this automatically in the real world, that color cast from light can really stick out like sore thumb in a photograph.

Just as the exposure controls on a camera enable us to compensate for the broad range of light intensity in the world, the white balance controls allow us to deal with the broad range of light color. White balance enables us to shift the color rendering, compensating for the color cast of the light source, and showing objects in their true colors as if they were lit with pure white light.

Sounds like a scene from The Lord of the Rings!

Two Parameters...

White balance parameters: temperature (left) and tint

Cameras and photo editing software generally provide two parameters for white balance:
  1. Temperature ‒ Sets amber-to-blue compensation. A regular incandescent bulb has a decidedly amber color cast. Dialing in the right amount of blue with the temperature parameter will cancel out the incandescent's color cast.  The unit of measure for the temperature control is kelvin just like color temperature. And the settings you use correspond directly to the color temperature of the light in your scene. In other words, whatever the color temperature is of your light, you would set this parameter to that value to remove its color cast.
  2. Tint ‒ Sets green-magenta compensation.  In addition to color temperature, different types of sunlight and fluorescent lights can create additional color casts in the green-magenta spectrum. This parameter is used to compensate for that.

... With Multiple Ways to Control Them

So, there are only two white balance parameters. But there are actually multiple ways to set these two parameters.
  • Direct ‒ You can usually set the white balance and tint parameters directly. Until you develop an eye for it, it's kind of tricky to do well though. The parameters have a really wide range of possible values, and just a little bit of adjustment can go a long way. So you can really screw up a photo if you're not judicious. But if you know what you're doing, you can really amp up the mood of a photo with these parameters. I generally find that it's easier to use a preset white balance setting to get in the ballpark then eyeball it and use very small amounts of direct parameter adjustment to dial it in.
  • Auto or AWB ‒ Using Auto, the camera evaluates the scene, calculating white balance settings in a split second between when you click the shutter button and when the camera takes the picture. There is a significant caveat to using Auto white balance: It only works reliably within a fairly narrow range of color temperature values, typically between about 3500K to 8000K. Sodium vapor; incandescent; halogen; many types of fluorescent; tungsten; "soft white" and "warm white" CFL and LED lights ‒ basically most types of indoor lighting! ‒ fall outside this range. That's why Auto WB is really hit or miss when shooting indoors under available light. Works pretty darn well outside in daylight though.Photo editing software usually has an equivalent Auto setting to evaluate white balance from a photo after it is taken. In my experience the camera's Auto setting is usually more accurate assuming the light is within its range. But it's usually worth looking at what your editing software comes up with to see if you like the look better. 
  • Preset ‒ Most cameras and software have several preset white balance settings corresponding to various light types ‒ incandescent, cool-white fluorescent, direct sunlight, etc. These presets dial in fixed white balance settings corresponding to the lighting type selected. They definitely get you in the range, and with indoor lighting they're often (but not always) more accurate than Auto. But they are not precise fixes given the variability in color temperature based on factors other than the type of light (as you learned in my previous white balance post). But they can be a good way to improve the color of your photos quickly and easily if things are out of whack.
  • Custom ‒ Most cameras have a feature to measure and store the white balance of a scene. The way it works is you place a neutral gray or white object (ideally a gray card made for exactly this purpose, but it can be just a plain sheet of white paper) in the middle of the scene so that the light falls on it. Then while the camera is in "white balance measuring mode", you take a picture of the object. The camera calculates the white balance settings needed to remove any color cast it is seeing on your gray or white object, and then stores those settings. Subsequent photos can be taken of the scene using the stored white balance settings and any color cast will be nicely neutralized. It works really well and is the most accurate method to neutralize the color cast from lighting. It's particularly helpful when shooting under mixed lighting conditions, where you have, say, overhead fluorescent lights, incandescent table lamps, and sunlight coming in from the windows all in your scene. The only issue is that it's kind of a hassle since technically you need to remeasure the white balance any time the light changes, which outdoors is happening continuously. Photo editing software has a similar feature in the form of the "eyedropper". You activate the dropper, then click on a neutral gray or white  object in the photo and the software makes the calculation and sets the white balance accordingly. So when you're shooting, you can just take an additional throwaway photo with your gray card in the scene and use the dropper on it later to get a correct white balance setting. If you forget to take such a photo, you may be able to use a white or gray object that just happened to be in your scene. The eyedropper is very effective and quicker than creating a custom preset in the camera.
Auto
A quick example. I took these three snapshots one after the other. The lone light source is the chandelier, which was loaded with incandescent bulbs. The first photo uses Auto white balance. The second uses the Incandescent preset. And the third is a custom preset I made using a grey card that I propped against the silver bowl on the table to get my white balance measurement.

Incandescent preset
You can see right off the bat that the custom preset has the most neutral colors and the light coming off the chandelier bulbs is white. It is a good representation of the actual colors of the objects in the room. The Auto and Incandescent settings produced pretty close results, but if you look at them closely you can see that the Incandescent setting retained a bit more of the amber cast.

After I took these photos I compared the previews off the camera LCD to the actual live scene and the one that had the closest colors to what my eyes actually saw in the room under that light was the photo using the Incandescent preset. Speaking subjectively for this particular photo however, I'd say that my order of preference is 1) custom preset, 2) Auto, and 3) Incandescent.

Custom preset

You Can, But Should You?

With these controls, you can now remove light-induced color casts from your photos and depict the "true colors" of things.

But imagine this: You wake up an hour before dawn to get down to the pier early to catch the sunrise over the ocean. Since you're putting in so much effort, you just as well get some custom white balance settings to ensure your colors are right. So you bring the gray card and get by-the-numbers-perfect white balance settings. You go home, happy in knowing that you captured the definitive photos of that location. A National Geographic cover is not out of the question. When you bring up your photos in Lightroom, the first thing you notice is that the photos don't look nearly as vivid as the scene did in real life. The whole thing is kind of washed out and desaturated. Your golden hour isn't very gold. Disappointment ensues. NatGeo doesn't call.

What gives?

Well, the color cast imparted by golden hour light is the whole reason it's called "the golden hour". Your custom white balance setting removed the gold, in terms of both color and mojo. Your "golden hour photos" have been turned into "hour photos". (Fortunately, you can restore it in Lightroom by ditching your custom white balance settings and dialing in a white balance that restores that wonderful golden hour warmth. Hint: Start with the "Daylight" setting and adjust from there. Whew!)

Golden hour light should be gold

So the moral of the story is: There are times when you definitely want to compensate for lighting-induced color casts. Heavy tints from indoor lighting (like my dining room photo above), mixed lighting conditions, and product photography scenarios all come to mind. But there are times when the color of the light is a key part of the scene and should be preserved, in whole or in part, in your photo.

And although we haven't talked about it, there are even times when you should consider using white balance creatively to enhance, or even manufacture, a mood in your photo. For example, dialing down the temperature just a little can add a sense of warmth and coziness that is just lovely for some types of photos.

White Balance Strategies

So that finally brings us to the most practical question of all. What's the best way to set your white balance?

Like many good meaty questions, the answer is, "It depends."

First rule, if you're shooting JPEG, it's much better to nail the white balance in-camera than try to fix it in post. It can be hard to remove color later from a JPEG file. If you're shooting RAW, it doesn't matter quite as much, except that your LCD preview image and histogram are going to be based on your camera white balance settings and you may be making exposure and composition decisions based on that preview and histogram. So it's a good idea to at least get the white balance in the ballpark.

Here's are some basic strategies, not all of which I'm too keen on:

Auto
This is the "set and forget" strategy. Put your camera on Auto white balance and hope for the best. This is going to work out pretty well for outdoor shots during the day, but it's going to suck for indoor photos using available light, or outdoor night photos lit by typical city lights.

Preset
Every time you start a session or change your lighting situation, choose the most appropriate preset and go with that. This is going to get you in the ballpark in most situations except scenes where you have mixed light. It will generally work better than Auto in lighting that is outside Auto's range, but worse than Auto in lighting that is in range. And it's a hassle having to set white balance so often. If Auto is "set and forget", then the Preset strategy is "set and reset, and reset, and reset, and reset..."

Custom
You could carry around a gray card and use a custom white balance setting every time you change lighting. That's yet more hassle, although you can avoid it by just getting a picture of your gray card under the same lighting and getting a correct white balance setting using the eyedropper during post-processing. Either way, you're guaranteed to get the true colors of objects. And you're guaranteed to nuke any desirable quality in the color cast of your lighting.

Auto-Mostly
I did this for a long time. I set my camera up in Auto, then if it didn't look right I'd fix it with a camera preset or in post-processing. If you shoot RAW, this is actually a decent strategy because it's low effort and you generally get acceptable results. But you will run into situations where you feel like you just can't zero in on a good white balance setting (typically in mixed light). Then it's kind of frustrating.

Situational
What I'm doing now is employing pretty much all of the various ways of setting white balance. Camera makers created so many different white balance options for the same reason they created so many different lenses. To make money! Because the best one to use depends on the situation.
  • In daytime outdoor scenarios (i.e. where the color temperature is in a compatible range), I use the Auto white balance setting.
  • When indoors under available light, the Auto setting isn't going to be accurate. So I use either the appropriate camera preset, or I create a custom preset and use that. I have a collapsible gray card that takes up very little room in my camera pack and is always available.
  • If I'm in a mixed light environment, or I'm taking photos where the colors absolutely-positively must be accurate, I create a custom preset. It's the only way to be sure.
  • If I'm shooting a photo where I want to retain the color cast, I'll just shoot with the daylight preset (which is essentially the "pure white light" setting) and then adjust it in post-processing if necessary.
  • And in all these cases, I do a final evaluation when post-processing and I may override what I did in-camera with a Lightroom preset or a completely custom setting. 
This approach requires a little more consideration and effort, but it gives good results in virtually all scenarios.

UniWB
There's one more way of setting up white balance that I can think of. This approach only applies when shooting RAW images, but it improves the accuracy of histograms and blinkies (for both the camera and editing software). But that improvement comes at the cost of horribly green-tinted image previews. It's called UniWB and it places a heavy premium on getting an exposure that is optimized for post-processing. A noble goal for sure. But honestly, the price you pay of losing a usable image preview is just too great for me to do it. But I mention UniWB as a strategy just for the sake of completeness.

Wrap It Up

So that's a pretty in-depth, yet non-technical, discussion of white balance. One can go a lot deeper with this and some some do (see UniWB above). But in terms of balancing the competing objectives of image accuracy, expressive freedom, and ease of use, I think this is the truly important stuff to know. At the very least, you should be armed with the information needed to avoid accidentally creating another blue dress / white dress meme.

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