Sunday, 24 September 2006

White Balance

Three images showing different white balance settings

Digital cameras have one very interesting advantage over good old film cameras: you can adjust settings that you would normally have adjusted by changing film. An obvious one is the ISO setting: one shot can be taken at 100 ASA, the next one at 400. A less obvious but very important setting is the white balance. This setting is meant to adjust the colour balance in different types of light so that white areas actually come out white. If you get the white balance wrong, the white areas in your shot will come out yellow or blue, depending which way you got it wrong.

Most DSLR cameras and some high end compact digital ones allow you to override the white balance, typically by offering a presets for tungsten or fluorescent light, cloudy or shade conditions, etc. But your specific lighting conditions don’t always match a preset. Some cameras allow you to provide a sun temperature equivalent in Kelvin but this is confusing if you are not an astronomer or a physicist. Finally some cameras allow you to specify a custom white balance by giving them a reference. I had never used this setting as I wasn’t too sure how it worked on my camera, until today when I picked up a copy of Mac User that has a very simple and straightforward explanation.

I decided that the subject for experimentation would be my bedroom, complete with unmade bed. Not that I want to pretend I am Tracey Emin but the wall behind my bed is the best white reference in my flat. To make my life easier, I composed the shot to ensure a large area of white wall would cover the centre of the image, as this is the area the camera will use as white reference.

  • The first picture is taken using the automatic white balance setting. Although the camera tried to compensate for the yellow hue produced by the tungsten light, it is still very yellow.
  • The second picture is taken with a preset white balance for tungsten light, which should be the right setting in this case. unfortunately, and probably because of the lamp shade that modifies the light, it is still quite yellow. Although, in this case, when seen on its own and in the original light, the mind adjusts and makes you think it is actually white.
  • The last picture was taken using the custom white balance seting and the previous picture as a reference. This time it is really white: I verified this by using the colour picker tool in Photoshop. The funny thing though is that seeing the shot on the camera’s LCD screen, on its own and just after the previous one, the mind plays tricks again and makes you think it is blue-ish.

Using a custom white balance produces great results. The only complication is that you have to take a reference shot and adjust the setting every time you change light condition but it is easier and quicker than doing that in Photoshop afterwards, especially if you take several shots in the same lighting conditions. Also note that, because it consists in comparing the balance of primary colours in a reference subject, this reference doesn’t have to be pure white, it can be light grey. So a photographic 18% grey card is an ideal reference object.

Tuesday, 19 September 2006

Nova 1

Less than £1000 to send a digital camera (nearly) into space and come back with more than 800 amazing pictures: this what a group of students from Cambridge recently did. This is beyond cool! Well done to the Nova 1 team! Beat that NASA!

Saturday, 9 September 2006

No Saddam link to Iraq al-Qaeda

We already knew that there were no WMD in Iraq, contrary to what the UK government said. Now we have the confirmation that there was no link with al-Qaeda either contrary to what the US government said. What a mess and what a waste of human life and resources! But more importantly what a travesty of so-called Western values of freedom and democracy! One Nation under God, indivisible, With Liberty and Justice for all, they say. Indeed, to the detriment of other nations' liberty and justice. Note that I have nothing against the American people, as I understand that the People are not the same as the Government of George W Bush, in the same way that the British People are not the same as the Government of Tony Blair. Isn't it time that the democratic process in both countries be put to work and make the clowns that are at the helm accountable for what they did, before more damage is done? Apparently, this is already happening in the UK and I wish it happened in the US.

Via BBC News

Another Goat Story

This time the action is in Sudan and is about a wedding.

Via BBC News

Friday, 8 September 2006

The Chicken and the Donkey: a story with a Moral

I just got this in an email from a friend and thought I should share:

On the farm lived a chicken and a donkey, both of whom loved to play together. One day, the two were playing when the donkey fell into a Bog and began to sink. Scared for his life, the donkey hee hawed for the chicken to go get the farmer for help! Off the chicken ran, back to the farm.

Arriving at the farm, he searched and searched for the farmer, but to no avail, for he had gone to town with the only tractor. Running around, the chicken spied the farmer's new Z-4 silver BMW.

Finding the keys in the ignition, the chicken started the beautiful motor car and the chicken sped off with a length of rope, hoping he still had time to save his friend&'s life.

Back at the bog, the donkey was surprised, but happy, to see the chicken arrive in the shiny BMW, and he managed to get a hold of the loop of rope the chicken tossed to him. After tying the other end to the rear bumper of the farmer's car, the chicken then drove slowly forward and, with the aid of the powerful car, rescued the donkey!

Happy and proud, the chicken drove the BMW back to the farmhouse, and the farmer was none the wiser when he returned. The friendship between the two animals was cemented: best buddies, best pals.

A few weeks later, would you believe, the chicken fell into a mud pit, and soon, he too, began to sink and cried out to the donkey to save his life!

The donkey thought a moment, walked over, and straddled the large puddle. Looking underneath, he told the chicken to grab his thing and he would then lift him out of the pit. The chicken got a good grip, and the donkey pulled him up and out, saving his life.

The moral of the story: When you're hung like a donkey, you don't need a BMW to pull a chick.

Thursday, 7 September 2006

Goat Free Roads

Out of all the possible excuses for driving above the speed limit, the one about the goat free roads is one of the best.

Thanks to The Register.

Wednesday, 6 September 2006


Yes, Xmas! My local pubs already have their Xmas menus out and we're not officially in autumn yet...


Newspaper headlines were saying yesterday Blair out by May next year. Today they are saying Blair out by Christmas. I suppose tomorrow will be Blair out by Sunday.