Lighting for Film & TV: Colour Correction Filters Pt 1: What is Colour Temperature?

31 May

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Colour Correction Filters
There’s more to it than meets the eye!

So I thought I’d do a series of blogs all about filters; what they do, how you use them and why they’re so damned handy…

OK, I know you may think that this isn’t perhaps the most exciting subject to read about, but it’s vital for all you budding Directors of Photography and Cinematographers out there, to understand that your ultimate aim is to master your craft, and that means having a deep understanding of ALL aspects of camerawork and lighting.

Mastery will get you to the top of your profession; being part of what I call the ‘Mediocre Majority’ will not, and knowing your craft will get you ultimate respect from your colleagues. If you don’t know this basic stuff, then when you work with experienced Lighting Gaffers and ‘Sparks’ you’ll gain zero respect from them, they’ll see you as unprofessional and treat you with contempt… quite right too!

I know I keep banging on about this but remember… a big part of mastering this craft means having a real in-depth understanding of anything and everything to do with camerawork.

So now I’ve had my industry rant let’s get down to work…

I’m going to divide this into a mini series of into 6 easy to understand parts:

Part 1 : What is Colour Temperature?

Part 2: Why Colour Correction filters are used to change colour temperature and how to use them.

Part 3: The most commonly used Filters.

Part 4: Effects filters and how to use them.

Part 5: How and why you use diffusion to soften a light source.

Part 6 : Bringing it all together a practical workshop on colour correction and filming using mixed lighting

So without further ado, let’s get on with…


Part 1:
Colour Temperature.

Before we get into filters you first need to understand something called Colour Temperature.

The human eye is a truly wonderful thing. It can change focus in a millisecond (certainly faster than any focus puller know!). It can adjust for a variety of light levels in an instant so that your field of vision has a perfect balance of light and shade (and doesn’t need you to take 6 light meter readings and then average them out!). It can flick from one area of vision to another instantaneously….(faster than the fastest whip pan you could imagine)…OK enough, you get the point! This isn’t a bloody biology lesson!

What I’m getting at is this: whoever comes up with a camera as versatile as the human eye will make Bill Gates’ bank balance look as measly as the day’s takings from a tea shop in a bleak, out of season, seaside resort – probably Bognor Regis!

Tea – White, no sugar, thanks Bill!

Forget your all singing, all dancing Arri Alexa, the good old eyeball makes it look a Box Brownie.

Anyway the one thing I didn’t mention that is relevant is that the human eye automatically compensates for colour variation. So, for example, if we are outside in bright sunlight and you move indoors to a dark room lit by a table lamp, all that will appear to change, is the light level.

Although the colour of the light in these two situations is totally different, the eye (or rather the brain) compensates by doing an instant Colour Correction. This instantaneous correction makes white appear white in both environments.  Film stock and digital cameras can’t do this so they need to be balanced for one particular colour and anything that deviates from that colour will produce a colour cast. So what exactly do I mean by different “coloured” light?

This difference in the colour of light is known as… Colour Temperature!

In its simplest form Colour Temperature is a component of light which relates to the value of its colour and its value is expressed in degrees Kelvin or K.

The Colour Temperature scale (click for larger version)

In film and TV Colour Temperature is generalized as either being warm or cold.

As you can see from this Colour Temperature scale, the lower the value of the light (or Degrees K) the more ‘red’ the light becomes. In the film and TV industry we categorize light in the 1000-4000 K range as being Warm. In practical terms this is the type of light that comes from household light bulbs (tungsten light) and candles. Anything from 6000-10,000K range is ‘blue’ and we say the quality of light here is Cold.  Blue light is a characteristic of daylight.

Incidentally you can see from the scale above that the mid day sun (on a clear day) is about 5,000K (Technically it is actually 5,600K but hey!)

Colour Temperature changes throughout the day: at sunset the colour temperature becomes lower/less intense (redder) because the sunlight is being refracted through the atmosphere in a different way to when it is directly overhead at midday.

So in a nut shell ‘The colour variation of light is referred to as the Colour Temperature and is measured in degrees Kelvin’.

Of course being enthusiastic students of all things to do with cinematography I know (or should I say, I will expect!)  you to learn more about Colour Temperature. Like most things, the more you study it, the more involved it becomes, but for the purpose of this blog, you have at least a very basic understanding.

So what’s all this got to do with Colour correction filters?

Basically everything, but you’ll have to wait for my next post to find out more. Have Fun!

Next time… Why Colour Correction filters are used to change colour temperature and how to use them.

Remember if you have any questions about anything don’t hesitate to contact me, I’d be happy to help! I really hope you’ve enjoyed this post, please be sure to share it with your mates (it’s free!!) – I want to try and get this info to the people who want it! Oh and please show your support by following us on facebook and twitter (it’s also free!!), and if you’re interested in receiving updates and future e-books then sign up in the email form to the right.

Finally, I run Lighting and Camera Operators Courses  so click the link or get in touch, if you’re interested in coming and learning in person!

Stay creative people and see you next time!

Chris.

Free Spirit Film & TV
Film, TV & Online Video Production.

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4 Responses to “Lighting for Film & TV: Colour Correction Filters Pt 1: What is Colour Temperature?”

Trackbacks/Pingbacks

  1. Lighting for Film & TV: Colour Correction Filters Pt 1: What is Colour Temperature? - June 12, 2012

    [...] Film Camera Course| Read the Full Article [...]

  2. Lighting for Film & TV: Colour Correction Filters Pt 2: How To Use Them « Through The Lens Film School - September 17, 2012

    [...] so this is the second blog all about colour correction, if you haven’t read the first one, here it is . If you have read the first one I hope you now have a very basic understanding of Colour [...]

  3. Lighting for Film & TV: Colour Correction Filters Pt 3: Daylight to Tungsten « Through The Lens Film School - October 2, 2012

    [...] let’s do a quick revue on colour correction so far; in my first blog in this series we’ve talked about the importance of colour temperature, how it’s measured and [...]

  4. Lighting for Film & TV: Colour Correction Filters Pt 4: Effects « Through The Lens Film School - December 3, 2012

    [...] filter can be used on both HMI’s and Tungsten light sources preferably lamps with a Fresnel lens so you can focus the light [...]

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