ON THIS PAGE:

Colour temperature
Light source table
The importance of white balancing
When to do one
White balance modes
Auto WB
Manual WB
Preset WB

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PART 2: WHITE BALANCE

by Christina Fox

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

Fortunately (or unfortunately) the camera isn't so easily fooled and so you will have to do a white balance.

To understand white balance you first have to understand colour temperature...

COLOUR TEMERATURE

If I put a poker in a fire it will start to glow "red hot" - if I put it in a furnace and really heat it up it will look as if it is "white hot". As the temperature of the poker rises the colour of light it emits changes. Red hot is pretty hot - white hot is very hot. There is a definite connection between the temperature of the metal and the colour of light it emits. This "colour temperature" connection is a way of scientifically quantifying the colour of the light source.

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 poker). The colour temperature of tunsten light is 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! Now the colour temperature of daylight varies through out the day, 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?

We have to tell the camera what colour of light it is working in so that the picture it records looks something similar to what our eyes and brain see.

To make white objects appear white to the camera we do a WHITE BALANCE. To do a manual white balance the camera must be shown something white (usually a piece of paper) lit by the light source you will be working in. 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.

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.

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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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EX1 WHITE BALANCE MODES

There are four white balance modes to choose from:

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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, the camera does not white balance quickly in automatic and needs time to get the colours right. Also, do be aware that the camera will be subtly but, constantly adjusting and changing the white balance, so there may be obvious colour changes when you edit shots from the end of a sequence into the beginning of a sequence.

You can select auto white balance (ATW) by:

Method 1

• Press the FULL AUTO button. A small green light will light up in the centre of the button once it is activated.
• However, by default this button also selects IRIS, GAIN and SHUTTER to automatic at the same time.

So, if you only want to switch white balance to auto – you need to assign ATW to either the B switch or an assign button…

Method 2

• Press the MENU button
• Scroll to the CAMERA SET MENU using the silver SEL/SET wheel. Press in to select.
• Scroll down to WHITE SWITCH <B>
• Select ATW

NOW you can choose only auto white balance by…

• Pressing the FULL AUTO button and ensure it is NOT lit.
• Select B using the silver WHITE BALANCE toggle switch to select ATW

However, it does mean that instead of having two manual WB memories (A and B), you now have only one: A for manual and B for auto. So if you prefer to keep A and B switch positions for manual operation….

Method 3

• Press the MENU button
• Scroll to the CAMERA SET MENU using the silver SEL/SET wheel. Press in to select.
• Scroll down to WHITE SWITCH <B>
• Select MEM
• Scroll up and press RETURN
• Scroll down to the OTHERS MENU. Press in to select.
• Scroll down to ASSIGN BUTTON. Press in to select.
• Select an unused button and assign ATW to it.
• Press the MENU button to exit the menu.

NOW you can choose only auto white balance by…

• Pressing the FULL AUTO button and ensure it is NOT lit.
• Press the chosen ASSIGN BUTTON to select ATW

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HOW TO DO A MANUAL WHITE BALANCE

1.    Make sure the FULL AUTO switch is NOT lit.

2.    Select WHITE BAL switch to A the W:A symbol will appears in the bottom left hand corner of the viewfinder/LCD.
3.    Point the camera at a white piece of paper and this time press the WHT BAL button under the camera lens.

In the viewfinder/LCD you will see the message.

AUTO WHITE BALANCE
         EXECUTING

When the white balance is done the message will change to:

AUTO WHITE BALANCE
       OK: ****K

Where **** is the colour temperature of the light hitting the piece of paper.

If you see the message NG: HIGH LIGHT or NG: LOW LIGHT the camera is having difficulties accurate white balancing because the white is too bright or too dark. Change the exposure manually or switch to auto iris, then try white balancing again.

If you have not assigned auto to the B memory - you will still have two manual 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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PRESET WHITE BALANCE

The Sony EX1 also has a preset white balance option.

It will assign a tungsten 3,200 Kelvin white balance to the preset selection as the default. This would be useful if you are doing a lot of shooting in locations only lit with tungsten light such as a studio 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 different white balance to the preset selection.

• Press the PICTURE PROFILE button
• Using the silver SEL/SET wheel select SEL. Press the wheel to select.
• Select PP1: STANDARD. Press the wheel to select.
• Select SET
• Scroll down to WHITE. Press to select
• Scroll down to PRESET WHITE: 3200. Press to select.
• Using the silver SEL/SET wheel change the colour temperature to the required setting.
• Press the PICTURE PROFILE to exit.

With PICTURE PROFILES OFF the PRST WB will be 3200K. But, if you select PP1 the PRST WB will be whatever you have set it to (You can set up to six Picture Profiles).

But you can choose to preset the white balance to any level from 2,100K – 10,000K.

Daylight is usually set to 5,600 or 5,800K.

  © 2000 - 2010

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Part 3

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Part 1: FOCUS

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Christina Fox