106 — White balance and why snow is blue

Pho­tog­ra­phy pod­cast #106 dis­cusses the often con­fus­ing topic of white bal­ance and why some­times the cam­era screws up our images like giv­ing us blue snow. Cor­rect­ing this is really easy and it just requires a bit of under­stand­ing of what is going on in the back­ground.  In a very tight over­sim­pli­fied nut­shell, when we see some­thing that has colour, it has that colour due to the colour tem­per­a­ture of the light source illu­mi­nat­ing it.

Light a can­dle in a dark room and look at a white base­ball; it will look orange. The same thing hap­pens with white snow that looks bluish under cloudy over­cast con­di­tions because cloudy light is bluish. Our eyes might not notice the blue because our brain com­pen­sates for the cast because it “knows” that snow is white, but the cam­era often gets it wrong. In this pod­cast we talk about white bal­ance, auto­matic white bal­ance, the white bal­ance pre­sets that your cam­era comes with and set­ting a cus­tom white bal­ance. If you’ve ever wanted to improve the colour accu­racy of your images, this photo pod­cast offers up some fast tips.

Left image — When we see an object that has colour, it has that colour due to the color tem­per­a­ture of the light source illu­mi­nat­ing it. This is why if we take a white base­ball into a room lit only by a can­dle, the base­ball looks orange. The same thing hap­pens when we take a pic­ture of white snow on a cloudy over­cast day and it looks blue. Right image — White light (the kind we see at noon on a sunny cloud­less day) is actu­ally made up of equal parts of Red, Blue and Green light. These are the pri­mary colours in photography.

Left Image — The camera’s AWB (auto­matic white bal­ance) didn’t ren­der this scene prop­erly and the snow looks bluish because the day was cloudy and cloudy light is bluish. Right Image — I cor­rected this in post pro­cess­ing and the snow looks more nat­ural to the eye.

This image was lit with 2 light sources; the light com­ing from the stove AND over­cast light com­ing in through the win­dows. AWB does a very good job here but is a hint too warm. The cloudy pre­set adds yel­low to com­pen­sate for cloudy light which is blue. In this case it repro­duces too warm. The Incan­des­cent pre­set adds blue to com­pen­sate for incan­des­cent light which is warm. Here it added way too much blue. The cus­tom set­ting, where you take a quick read­ing from a grey card or use a tool like an Expodisc was the most accu­rate and best repro­duced the scene.

Links /resources men­tioned in this podcast:

Spin­rite - To recover crashed hard dri­ves
Allan Lev­ene is run­ning for con­gress!
Grey cards at B&H — Expodisc at B&H — Color meters at B&H
Pho­tog­ra­phy tours in Mon­treal — One to one pho­tog­ra­phy instruc­tion by yours truly

- Wide open aper­ture is our reg­u­lar forum assign­ment for May
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Pod­cast: Play in new win­dow | Down­load