Sunday, November 11, 2012

Consistent White Balance?

Recently I was on a shoot for a client, which I might add was great fun. I had an opportunity to use a 5ft Octa Softbox in the field as oppose to just experimenting with it. The light produced by it is amazing but this post is not about the Octa and its great light though I could go on and on about it. While photographing for this client I used both the modeling lamp to take photos as well as light from strobes. In both cases I set a different white balance so the photos look consistent. 

Before I go on about the consistent aspect of white balance here is a brief about white balance. Whenever we see a things in real life our eyes automatically adjust for any colour cast which may be there in the scene. So if you take a white peace of paper and held it in sunlight it would appear white to you and if you held it under a tube light (florescent light) it would still appear white to you. However, your camera does not work that way. There is a setting called "Auto White Balance" (AWB). For the most part it does a good job of picking out any colour cast in the scene and correcting for that colour cast and giving you a photograph with its neutral colours.

Now comes the interesting bit, your camera calculates it every time you take a photograph. So if you cast a small shadow on something while taking a photograph and then you move back, your camera will have a different white balance between shots. This is fine if the colour consistence between shots remains, but this does not happen in a lot of cases. So let say you are shooting a landscape where do don't cast a shadow and your camera is set to AWB.  If you move one meter either to the left or right there would be a different white balance. If you shooting jpeg then you mostly cant fix it in post processing. If you raw then you can fix it in post processing. (The difference may not be very significant to notice at first but in most cases its there)

White balance varies from mostly having a blueish colour cast to a reddish colour cast on the photo with varying tints. If the colour temperature is higher then you have a blue colour cast and if the colour cast is reddish then the colour temperature is low.

Colour temperature is measured in Kelvin and 5000 to 5500 K is daylight colour temperature. Tube light (florescent light) it has a blueish colour light with a green tint. This is at about 6000K to 6500 K . Many times a blue filter is put on a lens or the light is gelled blue when someone wants to make the photo look cool. This is used for auto-mobiles photos. A red filter is used to in case of sunsets to exaggerate the colours. 

Here is then interesting thing, white balance is not that important! (well sort off). You might be wondering after having blabbered about white balance so long I am now saying its not important! Well for the most part it is a creative choice. You can pick a white balance and set it to have an affect, but picking a white balance gives you constant colours from shot to shot. However, white balance becomes important when you are photographing a product or a building perhaps(especially for a client), in such situations representation of accurate colour is required. It is also important when you are photographing people. You don't want different colour cast shot to shot. In such cases you would worry about consistent colour and white balance.

If you wish to get consistent colour using a gray card and setting a custom white balance for different lighting conditions  would get you constant colour. In case of my client shoot, I was on location and the rooms were painted blue. When the light bounced off the walls it had a blue colour cast, though I had picked a white balance it was not accurate enough to get me actual colours. Fortunately I was shooting raw and using the eye dropper I was able to fix the white balance problem with a single click and did a batch edit. 

Here is one photo from the shoot with and without the white balance being fixed. PS -This was clicked when I was done with my shoot and is not part of the office shoot 

Here are some more links on White balance
Color balance