ON THIS PAGE:

Colour temperature
Light source table
The importance of white balancing
When to do one
White balance settings
Manual WB
Problems white balancing?

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PART 6: WHITE BALANCE

by Christina Fox

To the eye - the sun, a fluorescent tube or a light bulb appear to produce uniform white light. In fact, different light sources produce different mixtures of the visible light spectrum.

These light sources appear as coloured light to the camera. But if we white balance we can make the camera see the world  the way our eyes see the world.

But before we get too far ahead - it will help to understand the colour temperature of light. Luckily you probably know something about this already.

COLOUR TEMERATURE

If you look at the video below you will see a toaster being switched on. You will be able to tell when it is ready to make toast - because the elements will be glowing red. You know that red means hot - you have already made the connection between the colour of the light given off from the toaster and how hot it is.

Lord kelvin worked this out this connection with heat and light too. He experimented with a black body radiator (not a toaster) but he say that as it heated up the colour of light changed.

OK now think about a light bulb - inside is a filament (made of tungsten metal). When you switch on the electricity, a large current flows through a small filament, it gets hot and starts to glow. (ie It behaves like our toaster). The colour temperature of tunsten light usually lies at around 3,200 Kelvin. It is actually a warm reddish orange light.

The sun is another main source of light. As you'd expect it is hotter than a light bulb! The colour temperature of daylight is around 5,600K (at noon). But it can vary through out the day. If you think of the most beautiful sunset you ever saw - you'll probably remember all the reds and oranges - not the blues.

So, colour temperature on the ground is pretty variable from as low as 2,000 Kelvin up to 20,000 Kelvin. The table below shows the range of temperature possible for daylight and the conditions that effect it (along with some other light sources).

WHY IS WHITE BALANCING IMPORTANT?

When the camera does a white balance - it analyses the spectrum of colours hitting a white piece of paper. It juggles these until the white paper looks white.

So, white balancing tells the camera what colour of light it is working in and what to do about it. Once the camera has successfully white balanced the pictures it records in that location will look something similar to how our eyes see the same scene.

You have to be careful where you white balance. Beware of white balancing in the wrong light source e.g. by a window and then shooting the interview in a corner of the room lit by tungsten light. Whatever light falls on your subject should also fall on the white paper you use to perform a white balance - then they will look the right colour.

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WHEN SHOULD YOU PERFORM A MANUAL WHITE BALANCE?

• In mixed light (e.g. in a tungsten lit room with daylight coming through a window).
• When shooting subjects lit by fluorescent light
• If light conditions are changing quickly (i.e. at sunrise and sunset when you want the shots to match).
• Every time you move from one source of light (e.g. outdoors) to another source (i.e. indoors).

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SETTING THE WHITE BALANCE

There are four white balance modes to choose from:

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In reality things are never as clear cut as they seem...

AUTO WHITE BALANCE	MANUAL WHITE BALANCE
		These picture were taken in my dining room - which is lit by tungsten light. On my computer monitor the manual white balance looks a little blue. While the auto white balance looks spot on. Preset 5,600 Kelvin looks orange - as expected. While the preset 3,200Kelvin looks OK. But in this case I think I prefer the auto.
PRESET 5,600K (SUN SYMBOL)	PRESET 3,200K (LIGHTBULB SYMBOL)

AUTO WHITE BALANCE	MANUAL WHITE BALANCE
		These pictures were taken in my garden. Between the auto and the manual white balance I prefer the auto. The preset 3,200 Kelvin has made the sky look very blue - as expected. But in this shot - it looks pretty good. The preset 5,600 Kelvin setting is probably more natural and closer to the real thing.
PRESET 5,600K (SUN SYMBOL)	PRESET 3,200K (LIGHTBULB SYMBOL)

HOW TO DO A MANUAL WHITE BALANCE

1. Set the AUTO LOCK switch to the middle position
2. Press the WHT BAL button to select manual
3. Select white balance memory A or B (either the A or B symbol appears in the bottom right hand corner of the viewfinder/LCD).
4. Point the camera at a white piece of paper and this time press the black tablet-shaped button marked with the symbol above it. The symbol will flash in the viewfinder/LCD while the camera is calculating the correct white balance.

If the symbol continues to flash slowly try again in auto iris mode - or go to auto white balance mode

You have two white balance memories. I always place daylight (blue) white balances in memory B. Then all white balances done in artificial light go in memory A. That way I can switch easily from one to the other as I move from one location to another.

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AUTOMATIC WHITE BALANCE

Auto white balance can be useful when you are moving from one location to another and don't have time to white balance. However, do be aware that the camera will be subtly but, constantly adjusting and changing the white balance so, it may be difficult to edit shots from the end of a sequence into the beginning of a sequence.

To select Auto White Balance

Either

Switch the AUTO LOCK switch (No 1 above) to the auto lock position. However, this will lock iris, gain and shutter into auto too.

OR

Leave the AUTO LOCK switch (No 1 above) in the middle position. Then press the WHT BAL button (No 2 above) until you see NO icons in your LCD screen connected to white balance.

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PRESET WHITE BALANCE

The camera has two preset white balance options.

You can assign a tungsten 3,200 Kelvin (INDOOR) white balance to the preset selection. This would be useful if you are doing a recording in a studio, locations only lit with tungsten light or it could also be used for shooting at night when most light will be tungsten or other artificial lights.

Alternatively, you can assign a Daylight 5,800 Kelvin (OUTDOOR) white balance to the preset selection. This would be useful if you are shooting in daylight or want to shoot golden sunrises and sunsets.

My recommendation would be to assign 5,800 Kelvin option to the preset switch. Because, the camera has a useful function that gives you the ability to adjust the white balance to give warmer or colder pictures (but, only if the preset is set to daylight). To do this you first must go into the menus...

1. Press the MENU button
2. Scroll down to the CAMERA SET MENU using the silver SEL/PUSH EXEC wheel.
3. Click on the SEL/PUSH EXEC wheel and select WB PRESET
4. Set this to OUTDOOR

The outdoor setting is now assigned to the preset white balance switch.

NEXT

1. Stay in the MENU
2. Scroll down to the OTHERS MENU using the silver SEL/PUSH EXEC wheel.
3. Click on the SEL/PUSH EXEC wheel and select ASSIGN BUTTON
4. Set ASSIGN2 to WB OUTDR LV+
5. Set ASSIGN3 to WB OUTDR LV-
6. Press the MENU button to exit the menu.

To see how this works.

1. Set the AUTO LOCK switch to the middle position.
2. Press the WHT BAL button to select manual
3. Select white balance PRESET a sun symbol appears in the bottom right hand corner of the viewfinder/LCD.
4. Now if you repeatedly press the ASSIGN 2 button the picture will look warmer
5. If you repeatedly press the ASSIGN 3 button the picture will look colder.
6. Each step adjust the colour temperature by 500 Kelvin. Adjust until you get the look you want.

TROUBLE SHOOTING

HELP! The camera won't white balance manually...

There are several possible reasons why your camera won't white balance....

Are the surroundings too bright or too dark.

If the picture is very bright the camera is getting too much information - if it is dark, not enough. If you have control over lighting conditions - change them. Otherwise try auto exposure and then a manual white balance.

 

 

The ambient colour temperature is too high or too low for the electronics to jiggle around with.

To make a decent attemp at a white balance the camera needs light that has a smattering of all the colours in the visible spectrum. Try using the preset white balance and adjust using the WB OUTDR LV+   and LV-  feature as mentioned above.

Just a thought... If you try and white balance under sodium lighting you'll probably fail. Sodium street lights are practically a big spike of orange light and not a lot else. In this case either....

1) Go to auto white balance

2) select the tungsten preset (the little light bulb symbol) - remember it's probably getting dark anyway (otherwise why are the street light on?) so the pre-set white balance will be OK because the majority of light around will be artificial anyway.

  © 2000 - 2010

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Move on to...

Part 7: BATTERIES

Or back to...

Part 5: THE SHUTTER

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Christina Fox