With more cameras on the market than ever before, there's a cornucopia of different recording formats and file types for cinematographers to learn and master. While this undoubtedly opens up all sorts of creative opportunities, it can also present a few confusing challenges when it comes to comprehending what each specific setting actually does.
For a long time, the higher end recording formats were locked behind the more expensive prices of higher end cameras, but in recent years manufacturers such as Sony, Canon and Blackmagic Design have entered the market with more affordable pieces of equipment that boast the same sorts of features. Chief among these is the ability to record logarithmically, or in 'Log'. This can be a great boon when producing a film, but requires a bit of understanding in order to use the functionality to best effect.
Over the next few articles, we'll demystify the secrets of Log, and in this first blog we'll start by talking about what it actually is.
A rigid spectrum means that very bright or very dark parts of the image can lose their detail
The origins of Log
The first real utilisation of Log in a digital sense can be traced back to Kodak's Cineon system from the 1990s. Essentially, the system was designed to get as much information as possible from film scanning, and transfer it into digital video files. To accomplish this, a new way of looking at contrast was used, and essentially that's what Log is all about. This is the point where things can get confusing, so bear with us and we'll try to keep it simple.
The traditional way that digital video would be recorded made use of linear recording for brightness, which as you might expect means that the relationship between brightness and exposure could be plotted on a straight line. For every doubling of light, an exponential increase in brightness would be perceived in the recorded footage. The issue is that such a rigid spectrum means that very bright or very dark parts of the image can lose their detail or experience other visual distortions. To boil it all down to a simple conclusion, the dynamic range becomes limited.
How is Log different?
Rather than delving into the mathematical complexities of why Log scales are nonlinear, all we need to know is that each segment of the scale represents the previous value multiplied by a consistent number. The result of this is a curve, where the information is better spread out to allow for more information to be recorded in data-dense areas of the frame. It can all get a bit confusing, but all that you really need to keep in mind is that recording in Log will map a specific gamma curve (often specifically designed for each brand of camera) to the sensor, allowing you to record in far more detail with a greater dynamic range.
What tends to throw people off when recording in Log for the first time is that the image looks very dull, dark and flat – the opposite of what you might be expecting from a recording mode that aims to capture more data. To avoid being confused by this image, it's wise to invest in a camera monitor that can translate your Log footage into something more similar to what you'd expect to see. This will allow you to record in Log, but without being deceived by the flatness, which can make judging exposure difficult.
The amount of detail between light and dark, specifically in shadows or graduations will be far greater
Embracing flat footage
This flatness is your friend, however, and gives you a huge amount to work with when it comes to grading. For example, the amount of detail between light and dark, specifically in shadows or graduations, will be far greater. It simply needs to be unlocked. To do that, an extra step of grading is required, translating the Log image back to something that appears more linear, but with all of that extra information.
This can be achieved in a few different ways, but one of the most common and useful is via the wonderful medium of Look UP Tables (LUTS). We've talked about the practical uses of these tables before, but they can also be used creatively to really bring the colour and highlights out of Log footage. To briefly recap, a LUT is a mathematical formula that interprets footage as a set of data and alters each pixel to fit a desired 'look'. There are many different LUTs out there, some of which emulate certain film stocks and others which have a unique style all of their own. Regardless of which type you use to make your Log footage pop, it's important to maintain grading best practice as well – ensuring each clip matches with the ones around it before applying the LUT.
So there you have it. A (somewhat) simplified introduction to Log footage. In the next part of this series we'll look at things from a more practical perspective, talking about how to use Log at different steps of production and post. In the mean time, be sure to get in touch if you have any questions or would like to know more.
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