What do we mean by White Balance?
What do we mean by White Balance?
An Article by Patrick McNair
Amongst
all the settings on your camera you’ll
find one for White Balance usually contracted to WB. This might be a button on
the camera body or a menu option or both.
When we photograph a scene we usually
want all of the colours in our scene to be reproduced faithfully in the photograph.
That is unless we are trying to be more creative. If we were shooting in white
light or daylight the chances are that all of the colours in our image would be
the same as the colours in the scene but of course we aren’t always
photographing in this type of light and it is more likely that we would be taking
photos when there are clouds in the sky or in low light when we need a flash,
or under fluorescent lights indoors.
If we don’t have some way of
‘telling’ the camera what type of lighting that we are photographing in then it
would probably ‘assume’ that we were shooting in white light and the result
would be that our photo would have a colour cast in it.
The reason that this happens is
that different types of light sources give off different colours. For example, an electric light bulb gives off a yellowish colour. The flame from a candle gives
off a yellowish-red colour and Fluorescent lights have a slight blue colour. The White Balance setting on your camera is one way of letting your camera know what type of light you are
photographing under.
When
you press the WB button on your camera or you access the White Balance menu
you’ll be presented with a list
of choices similar to those shown below:
From that list, you would choose the
type of lighting that is a close representation of the ambient light in your
scene. So if you are shooting on a cloudy day, that’s the WB option that you’ll
choose or if you are in a room lit by fluorescent lights then you would choose
that option from the list.
When you do this, the camera will
compensate for the fact that you are not shooting in white light or daylight
and it will adjust the colours in your image accordingly so that they match as
closely as possible the original colours in the scene you are photographing.
You’ll see that, among the white balance options you have one that says ‘Auto’. Just like any other auto setting on your camera, that option gets the camera to make the choice for you. If you select Auto, the camera will use its built-in light meter to determine what type of lighting is illuminating the scene and it will attempt to compensate appropriately however it doesn’t always get it right and so, if possible, it is a better option to set the WB yourself manually.
You’ll see that not all of the possible
light sources are catered for in the white balance settings and your available
choices are pretty generic. A cloudy day where I am, for example, might not be
the same as a cloudy day where you are. Modern cameras will normally also have
a more accurate way of setting white balance based on colour temperature.
Don’t think of colour temperature
in the same way that we describe the temperature of something that gives off
heat. Colour temperature is used to describe the appearance of light and it is
measured on a scale called Kelvin (K). You don’t really have to understand the
physics of colour temperature only that it can be used to describe the colour
of the light source that you are photographing in.
The following chart shows the
colour temperatures of the most common light sources that you would find
illuminating scenes.
You can use the cursor keys on your
camera to position the cursor over the colour on the grid that closely matches
the colour cast that you are seeing in your test photos for the scene you are
photographing. For example, if the colour cast in your photo seems to be
slightly blueish then you would set the kelvin temperature to one that goes
towards the yellow colour temperatures e.g. around 3000K. If the colour cast is
yellowish then you would move towards the blueish colour temperatures e.g. 5000K. Of course with this approach, you
are having to take test shots at each adjustment.
An easier approach is to switch the
camera to live mode and look at the screen after every adjustment to see how
the colours appear to the camera.
You can also set the white balance
using a card, normally called a grey card.
This card is usually 50% grey.
You’ll sometimes get a card like this in a photography book or you can buy them
online.
The way that this works is that you
place the grey card in the scene with the scene being illuminated by the light
that you will be photographing under. You would take a photo of the grey card
with the card filling the entire frame of the photo and use this in your
camera’s custom white balance settings to ‘tell’ the camera that this card
should be grey. Once the camera knows that this is what grey looks like under
that lighting it can then adjust the colours in the scene to appear as though
they were shot in white light.
The menu options for this differ from
manufacturer to manufacturer so it is worth checking your camera manual or
videos on YouTube for specific instructions relating to your make and model of
camera.
There is another way that you’ll
see these grey cards used and that is in studio photograph where a portrait
photographer, who is shooting with the camera tethered to a computer, would
place the card in the scene lit as they intended and then take a test shot.
They could then use a dropper tool in the software to ‘tell’ it that this
should be grey and, as they take subsequent photos, the software adjusts each
image as it is taken to compensate for the lighting.
All this will work as long as the
lighting in the scene is not changed. If it is then the process needs to be
carried out again.
As a final note, there will be times when situations make white balance more of a challenge. For example, you may be photographing in environments where the ambient light is made up of different types of lighting which. Taken together, create a mixed lighting scenario. There are ways around this, both in-camera and later in post-production but meeting a challenge like that is for a later discussion.
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