Overview
If you've been editing or coloring for a little bit, you're likely to have heard these terms, but you may not understand what each one means. Knowing the differences will help inform which camera you shoot with and which post-production workflow you choose, so make sure you're brushed up on these three formats before you start production.
Raw
Raw video isn't even video. In all digital cameras, the image is captured by a sensor that outputs raw chroma and luma information. Most digital cameras immediately convert that data into video files, but cameras that shoot in raw save that data directly. Using raw footage requires converting it to video files in post-production, which can be time consuming, but it does come with some crucial advantages:
Raw footage captures exactly what the sensor sees, meaning that no white balance, ISO, or color adjustments are baked in to your footage. This is incredibly valuable when color grading your project; raw footage will offer you a degree of latitude that no other format can.
Uncompressed
Raw footage, despite what the name implies, is not necessarily uncompressed. Most cameras that can shoot in raw, like the RED series, do encode the raw data to achieve more manageable file sizes.
So what is uncompressed footage? Well, it's a bit of a myth. There are a few cameras that offer truly uncompressed footage, meaning that in every step of the capturing and recording process, they do not make any adjustments to the footage to diminish its file size. The vast majority of cameras, however, do compress your footage in some way or another. That might sound like a bad thing, but the reality is that most in-camera compression is lossless - you wouldn't be able to tell the difference between the uncompressed version and the compressed one.
Log
There are a variety of log formats. Sony has S-Log, Cannon has C-Log, and ARRI has Log-C. Despite minor, proprietary differences between the three subsets of log, they behave very similarly. As with many of the behind-the-scenes elements of a camera, log footage is the result of a lot of complicated math that we won't go into. The important thing to know is that shooting in log offers you a high dynamic range, which allows greater flexibility in color grading. Unlike raw footage, however, log footage is video, and will come with a white balance and iso baked in.