10 January 2012

Let's get technical - White Balance

No smart-ass title this time because I am in a bit of a rush while I pen down this article :p Photography-workflow follows the age-old quality philosophy of 1-10-100. If you weed out an anomaly or unwanted element at the first stage you will need 1 unit worth of effort. If it is attended to at the next stage, the effort required multiplies ten fold! Often we ignore the camera settings while clicking a pic because of a repetitive consolatory voice in our head that goes "photoshop hai na" :) But when you have too many clicks from a photoshoot to edit, believe me, you'd wish that you had customized the camera's settings to avoid making simple corrections to images in photoshop at a later point in time.

What is white-balance (WB)
Having pointed that out, let me talk briefly on the subject on white-balance in photography. Please understand that your camera captures the light reflected from your subject, the light which has originated from a light source like a CFL or halogen bulb, or a tubelight or natural day-light. The natural daylight contains a spectrum of colors across the VIBGYOR range which combine to form the seemingly colorless light. Artificial light sources usually have a specific light color (also labelled color temperature) which is not very obvious to the human eye but greatly influences the camera sensor. Such artificial light sources, like ones mentioned above alter the white balance of the image with their color temperatures. For example, CFL lamps have a greenish tinge to their light - our eyes see these bulbs as bright white but the camera sensors sees the light as green; halogen/street lights have a deep orange shade. Also, if the subject is in the vicinity of a colored reflective surface like a shiny carpet/curtain/table then the light falling on the camera will contain that color and hence the whitebalance of the entire image will be screwed up.

This has bugged me often in weddings. There's a lot of sickening yellow in the air. Ladies don yellow colored sarees and drown themselves in an uninhibited display of gold. I hate it when I forget to correct the white balance on the camera - I shoot anywhere between 200 to 500 images which I later have to correct painstakingly in photoshop. It takes me even a week at times to make such simple corrections :(

So coming to the topic at hand, if your light source is artificial, you should click a test image and check if it correctly reproduces colors as seen by your naked eye. The color alterations are more evident in dark areas like areas in the shadows.

If you know the light source that is causing white balance alteration, you can choose from the below preset whitebalance modes.
Image Courtesy: cambridgecolor.com
What any whitebalance setting does it that it compensates for the excess of color in the environment. For example, the light source is flourescent, like CFL lamps, setting WB to flourescent will add light on the other side of the light spectrum to compensate for the excess flourescent light in the environment. So, if your scene is lit by incandescent bulbs, your light is orange. The Incandescent WB will cause your camera to add a lot of the opposite color, blue and cancel out the excess orange light, thus giving you an image that is closer to actual colors.

Preset White Balance

These are some common WB modes that you would find on cameras:
  • Auto – this works well in most cases but it's better to try the preset or custom mode for a mishmash of light sources.
  • Tungsten – use this in case of bulbs or high-temperature light sources. This mode produces a cooling effect which reduces the REDish light tinge in the image.
  • Fluorescent – this is the opposite of tungsten and warms up the image.
  • Cloudy – this setting generally warms up the image a bit.
Custom White Balance
In a situation where there are multiple light sources or too many reflective surfaces producing a non-standard whitebalance like tungsten/flourescent/cloudy, etc use the custom white balance feature of your camera. What you need to do is simply point out to the camera, the object/surface that is actually white. So what you are telling your camera is "see..this object is actually white but the light source is making it look blue/orange/green or whatever..". So the camera calculates the correction to be made to make that object look white under that light source and applies the same correction to all objects in the frame! Simple ain't it? :)

That's how simple the concept of white balance is folks! So the next time you are out shooting dozens of pics, please keep a checklist ready and include white-balance checks in it.

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