Today we are starting an essential and major series of articles that we are calling 'the video basics' but they could easily be called 'the refreshers' for those who need a quick reminder of what they already know. Subjects range from Apertures to Tungsten lighting, from Green screens to panning speeds and from Hyperfocal Distance to Persistence of Vision. All from video evangelist John Keedwell GBCT at the Epics Video Academy.
The series has it's own home on definitionmagazine.com. Part One is below.
Part One - The Camera and the Eye
The camera is a machine like any other, that only does what the operator tells it to do. It will normally respond by slavishly following your commands even if what you are telling it is absolute rubbish and stupid! It is very much like a computer, if you have heard the term 'garbage in garbage out' (GIGO) it is the same with the camera! If you tell it to do something outside its parameters it will come and bite you, albeit in a very submissive way! The camera doesn’t know what you want to do, so you have to tell it exactly what you need to do, and how you want to do it.
This section covers cameras that have a degree of control on them, such as white balance and colour balance etc. Many reasonably priced video cameras will do a fantastic job for 90% of the time you use them, then when you want to do something slightly different it won’t let you do it! Ideally you can take control and have a manual over-ride to your camera but if not there are several ways around getting what you want with a fully automatic camera, you just have to think differently when you’re shooting.
So assuming you have a control on your white balance you need to tell the camera what is white. I will discuss in another entry how lights are in different colours, so the camera might not understand what you may want to do. So at the start of the day or any change of location or lighting conditions you will need to do a white balance and the black balance. This is quite simple! It means finding a piece of white paper for somebody to hold a few metres away, you then switch the aperture to automatic for a moment, zooming right in to the paper so it fills the screen, and press the white balance button on the camera. Wait for it to do its business and it will then normally come up with a number in the eyepiece such as 5400K, for example.
This tells you the colour of the light hitting the paper is that absolute value. Now do a black balance the same way although you do not need the paper as the camera will 'self cap' and make its own black. Ideally you then do another white balance, so it’s white black and white. Now when you put the aperture back to manual and zoom out the lens the colours should be a natural representation of white to black and all the relevant colours reproduced correctly in between.
Intentionally fooling your camera
One trick here if you are confident! If you have a particularly cold day (perhaps you are filming in Britain!) and whatever you do everything looks blue and cold even after performing a white balance. Even your actors or your screen talent looks blue! If it is looking like watching the film Avatar then you need to warm up the light colour and make it appear warmer.
You can trick the camera to make it appear slightly more orange. This is done by putting a light blue filter over your piece of paper and then white balancing. Boom! All of a sudden your skin tones of your subject are warmer and it looks like a sunny day.
I used to do this a lot with lighting filters over the lens until Warm Cards were introduced as a commercial product. Darn it why didn’t I do that? These are gloss-free laminated pages with slightly different degrees of warming up or cooling down.
Remember if you white balance on the blue the subject will appear warmer (more orange) and vice versa. I often use this technique to warm up a person’s skin on the day. Please don’t overdo this!
Most of this warmth can be added in a post production colour grade, yet often it can be left out of the schedule to grade the finished video, so this is a down and dirty quick trick to do on the day of a shoot that is consistent and repeatable. Remember to do it on all of the scenes otherwise it will jump out as being a different colour!
I have already shown the eye can see into deep shadows and bright highlights and a camera is not normally as adaptable in its range, so we have to expose video sensors extremely carefully if we are to stay in control. Correct exposure of video is essential to understand if your pictures are to be able to be used. Most average scenes consist of shadows and dark places, mid-tones which are most of the useful parts of the image, and highlights should render as very light grey or 'Peak White'. We have to keep the average scene we shoot within this limit and so have to expose our image carefully.
For simplicity a camera can only 'see' or record in a range of 0-100, with 100 being white and 0 being black, (it is more complex than this but I’m trying to make it easy to understand here). However if this scene is overexposed and what you want to appear be a light grey or light tone of any kind with a value of say 90 - this is pushed to the top of the limit at 100, there is no way it will ever look grey when you show it back. The sensor chip has maxed out at 100 and it will look pure white. All the detail you may have wanted in that area will be lost forever, and will just appear white. This is particularly bad if you overexpose a face, as it will either appear to be very shiny and white, with the mid-tones of the (Caucasian) face being bleached out and this will not be recoverable in the edit, so be warned!
For more information about this and many more articles follow this series of articles or take a closer look at the following websites.