Wednesday, March 14, 2012

Introduction to White Balance for Digital Camera Users (Part II)

Martin Luther King, Jr. Memorial Dexter Avenue Church, Montgomery, AlabamaLast week, in Part I, I discussed the concept of white balance and defined it. The general idea of white balance is to get objects which appear white to human eyes/brains to be rendered white in your images, so the rest of the colors will render properly as well.

I also discussed the important concept that sometimes, things we consider to be “white” aren't always white when we look at them, and that it's not wrong to ensure they don't look white in our images. During the “golden hours,” for example, white can appear “golden.” At sunset white buildings can take on red and golden hues.

This week I'm going to discuss the practical side of getting your white balance “right,” or at least as “right” as you can get it, so the colors in your saved image are rendered as you saw them.

I use specific settings for white balance for virtually any artificial light other than my Nikon Speedlights (electronic flash units) which have the same color temperature as daylight, and whenever the sun is heavily filtered such as when there's heavy cloud cover. If I'm at or near direct sunlight lighting the scene, then I'll use auto white balance.

When taking photos on a heavily cloudy day, or if my subject is well shaded I'll use the appropriate setting for white balance; “Cloudy” or “Shade”. If it's a bright sunny day, I'll leave the white balance on “Auto,” and if some light clouds get in the way at different times, it won't matter as “Auto” can handle that. If I'm in an office building and taking available light photos, I'll probably set my white balance to “Fluorescent” as that's likely the predominant light source.

It's generally straight forward getting your white balance setting “right,” or at least very close for the situations I've described, which are more likely than not what most photographers encounter when in their home area or traveling. There are occasions when setting an accurate white balance can be difficult.

At times you don't know the precise type of light illuminating the scene. For example, fluorescent light comes in many types. It's also possible, especially inside, you might take photographs of a scene lighted with a variety of light sources.

Not long ago, I photographed a synagogue sanctuary during the day. The sanctuary had varied light sources including: sunlight through stained glass windows, fluorescent light, halogen light, and LED light. Each has its own color temperature, and together they have an aggregate overall color temperature.

If you have a small digital camera, you're going to have to use “auto white balance” or make a guess, but if you have a good consumer or professional level DSLR you can set a custom white balance. Nikon calls it “Preset Manual” white balance.

Setting a custom white balance isn't very hard. You let the camera read the color temperature of the scene and create the white balance setting itself. While the mechanics of creating the setting aren't hard, it's not quite a simple as it sounds.

You must account for two factors; where color temperature measurement is taken, and what target should be used to get the best possible reading of the scene's color temperature.

The best place to take your color temperature is exactly where your subject is located, but you need to be careful, that you don't affect the scene's lighting by interfering with any light falling on the subject. Just by standing in front of the subject, you could block one or more light sources, to some degree, causing the white balance reading to be inaccurate.

Please note, in a room with multiple light sources, different locations in the room can have light with different aggregate color temperatures. You might have to take a color temperature reading in the various spots you'll be taking photographs.

To measure white balance, you could simply use a white sheet of paper held in the light of the scene, as your target. I use custom white balance often and find using a white sheet of paper is not the best choice. For many years, the default target for white balance was a white card, or an 18% gray card. They're durable and easy to bring with you, however, there are times when they are as problematic as a white sheet of paper.

To obtain a good color temperature reading, you've got to take your reading with your camera focused solely on the white sheet of paper, white card, or gray card. That generally means you'll have to get very close to them, and possibly interfere or block some of the light you're trying to measure.

I use an Expo Disc, white balance filter, to measure my scene's color temperature, inexpensively and easily, without the problems discussed above. There are other similar products on the market.

The Expo Disc is a specially manufactured device which lets the light of the scene come through it, while you hold it or screw it on, directly over the front of lens. It acts just like the white card in that it lets your camera measure the color temperature of the scene and create a white balance setting.

The Expo Disc has the substantial advantage, that you stand where you'll take your photo, yet aim the camera directly at your scene ensuring an accurate color temperature measurement. That eliminates you interfering with the light illuminating the scene you're photographing.

With a good “white balance” setting, you can capture your scene in your photograph as close as possible to how you see the scene.


Jean said...

What a great pair of articles Ned. I have learned so much, and now understand why on very cloudy days my colors have been off, and what I need to do to avoid the problem in the future.

Your blog is a do not miss.


Stephanie said...

Hi Ned,

I see there are two Expo discs. I'm confused. Which one do you recommend?

Ned S. Levi said...

Hi Stephanie,

I understand. I suggest the ExpoDisc Professional Digital White Balance Filter - Neutral. This is the general purpose filter. The other ExpoDisc is a special purpose model.

The one for portraits shift the color so your white balance will produce "warmer" color, which is, in my opinion, nice for portraits, but not at all suitable for other uses. Even for portraits, I prefer the "neutral" filter. I can always make the portrait warmer in post processing, with little problem.

Paul said...

Ned, do you ever dial in the exact color temperature of a scene by using your camera's ability to put in temps in degrees Kelvin?

Ned S. Levi said...

I once borrowed a meter which could read color temperatures from a friend who does catalog work. I also do some catalog work, but have used the Nikon "Preset" and have gotten good results. I also put a color checker card in the photos, so I can make precise corrections in Photoshop.

I wanted to see if I could benefit from the meter, which would enable me to dial in the precise color temp into my camera.

I will tell you the meter and dialing in the exact aggregate temp was dead on, but using Nikon "Preset" works just as well.

If I needed to get my color balance that close all the time, such as what photographers need for catalog work, I'd get the meter and use it for all kinds of situations.

I just don't do that kind of work that often.

For my travel photography work, and my other work, using the ExpoDisc and Nikon "Preset" is just fine. Plus, I can always correct the white balance in Photoshop as I save virtually all my photos in RAW (nef).

So after dancing around your question, no, I don't use that ability in the camera.

Jon said...

Ned, I think I'm missing something here. If a location has different kinds of light sources won't the white balance be off according to where you subject is?

Ned S. Levi said...

Jon, I'm not sure I understand your question, but I'll give an answer based on what I think you mean.

I think you're asking that with several different light sources shining on a subject can you get a true white balance reading. The answer is unless the lights are shining discretely on different parts of the subject of your image, there is no problem. An example is the light from the sun which has many different wave lengths of light, all with different color temperatures. When they shine on an object, they blend for viewing by our eyes, and cameras. The same is true for artificial light.

On the other hand, the light blend may be different in different locations in a room based on a variety of factors including light intensity, distance from the lights to the subjects, etc. So, you will need to determine the white balance in the different locations where you will be photographing. For example, at my synagogue sanctuary shoot, mentioned above, I made multiple white balance settings, which were all somewhat different due to the light combination aggregate in each location.

I hope this answers your question.

Jon said...

You answered my question. Thanks.

Marshall said...

Great article. I finally have a usable understanding of white balance now. Thanks.

Anonymous said...

I agree with the previous commenters, this series of articles is very helpful.

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