Auto White Balance vs Custom White Balance – When to use which?

In this lesson we’ll go over a very important topic – white balance. I’ve already covered how to set custom white balance earlier, so we’re going into the details here, with tests.

The questions we want answered:

  • Can we always use auto white balance (AWB) instead of presets or custom white balance?
  • How accurate is the auto white balance anyway?
  • When to use AWB, standard white balance presets and custom white balance?

Let’s start with a quick video that runs you through the tests:

Download Video

Notes on test:

  • Both fluorescent (23 W) LED (10 W) lamps are rated at 6500K. The custom settings are only off by 100 K, which is absolutely okay.
  • The tungsten filament (200 W) is usually at 2800K, and I’ve rated it at 2700K, which is also within tolerances.

VERY IMPORTANT!!

Do not white balance in S-Log2 or 800% Hypergamma modes. Here’s Sony’s official wording on the subject:

Setting [ITU709(800%)] or [S-Log2] may cause an error in the white balance custom setup. In that case, set the exposure bright first and then perform custom setup.

Here’s a picture of my setup:

TestSetup

Here’s a recap of the answers, for your reference:

How accurate is the AWB on the Sony A7s?

Here are the results for you to study (click to enlarge):

LEDwb

FLwb

Tungstenwb

TDimmed

What should you be looking for? Simple. In the box on the far right, look at the percentage numbers below the white and grey patches. If the white balance is spot on, the white and grey patches should read 0%.

Notice something strange?

The Sony A7s does a damn fine job of ‘white’ balancing, because every single one of them has a perfect 0% for the white patch. However, this is slightly misleading, because the grey patch isn’t 0% for any of them.

The percentage for the gray patch for fluorescent and LED lighting is just 2%, across the board. This is perfectly acceptable.

While for tungsten, whether it is AWB or custom white balance, the grey patch is at about 10-11%. This is NOT acceptable.

Also notice how, in the Resolve-corrected (using the chart feature) Tungsten versions, the skin patches look really off.

Now, compare the percentages between AWB and custom for each light, for each patch. Is there any difference? No! That tells you, as long as the white balance is within the standard presets range (2800K to 6500K), the AWB is surprisingly accurate. When you are in the red zone, as in dimmed down lighting or fire, etc., it is dangerously inaccurate.

However, visually, they don’t look the same! Accuracy be damned here.

Takeaways:

  1. Use AWB only with daylight fixtures or daylight conditions. Avoid for Tungsten.
  2. If you have to use AWB for tungsten for some strange but misguided reason, please give the camera 30 seconds to adjust.
  3. For tungsten, do NOT use the color chart in its default state, which is to balance to 6500K temperature (inside DaVinci Resolve).

Personal suggestions:

  • How to white balance: I have got 100% success rate using Movie mode at 0+0 exposure. Use this to set white balance and then move on.
  • I prefer how my custom balance looks to what Resolve does! Agree?
  • Tungsten lighting makes even a chart look beautiful. The LED offers a bluish cast (15% variance in the blue chip), while the fluorescent offers a green one (15% variance in blue, and about 11% variance in green). This is why I use tungsten whenever I can, even to light my own videos for this guide. I have both LED and fluorescent fixtures I can use, but I always pick tungsten – unless a high-level executive is sitting opposite – which I’m not!

Can we always use AWB instead of presets or custom white balance?

Simple answer is No. You shouldn’t use auto white balance unless you are in a tough spot. It should be your last resort.

Here’s the order of usefulness:

  • Always use custom white balance, no matter what the situation.
  • WB presets are a second option if you’re short of time (see next).
  • AWB is only to be used if you’re totally desperate. Do not make a habit of using this, please. Even if you’re using it, try not to use it with varying tungsten lighting or early morning blue skies. You will have a really tough time in post.

When to use presets

Presets are handy things. There is only one condition in which presets are helpful, and that is when you’re absolutely sure of your lighting.

E.g., if you know all your tungsten lamps are around 2800K, then you can set your white balance to Tungsten.

However, in many situations, you are not completely sure. If you’re shooting in someone’s home, and they have a fluorescent or LED lamp that cannot be trusted, then you are better off with custom white balance. I have seen big-name DPs ignore this, quite possibly due to laziness. It’s all a question of developing the right habits. You just have to learn it once, and it holds true for any camera anywhere anytime.

I hope this lesson will help make your shooting choices a whole lot easier!