Viddovation
Veteran
This Log vs linear raw conversation is one that I've seen butchered numerous times before. As starcentral has partially alluded to, it's important to understand that the image pathway is composed of multiple pieces. When photons (light) hits the sensor photosites it's converted into an electrical charge. More photons (light), a greater electrical charge. But the photosite is like a bucket - too much light and it overflows. These photosite voltages are analog. The next step is a A/D converter that converts the electrical charge into a number for each photosite. Typically these numbers are generated in a linear fashion, meaning that a doubling in voltage produces a number twice as large. But the A/D converter is limited by two factors: how precisely it can read the voltage, and how many bits it has to store the results.
Practically speaking, the A/D converter is always going to use a higher bit depth than the final signal path or recorder outputs. In some cases for linear raw the bit depth of the A/D converter and the record path can be equal, but for video or log output this simply doesn't make sense. The reason being is that our eyes don't perceive light in a linear fashion. In fact, the downside of linear raw is that that it allocates a tremendous portion of it's storage bits to highlights and very little to the shadows. While this can be useful in situations with extreme highlights, it's not terribly useful for recovering from the shadows. Log by comparison makes an effort to use a DSP (digital signal processor) to reallocate the linear values from A/D converter into log encoded values.
Absolutely - 16 bit raw is incredible. But when you're looking at cameras storing log and raw values at 10bits and 12bits, it really deserves a more careful look at the math. For instance, the Sony F35 has a max output of 12bit RGB 444, but it uses a 14bit A/D converter, where the RED One MX used a 12bit A/D and 12bit linear raw encoding. When you look at the math that way, and remember that the linear raw file is over half highlight information, it's a bit easier to understand why people though the F35 had more pleasing skin tones - it was using more pixels to store where the skin tones were exposed.
Of course the F35 is dated now, but I suspect it's 12bit RGB 444 will be a very competitive image against the FS7 12bit RAW.
So, in my opinion, if it's coming from a good enough A/D converter, I do think that Log gives you the majority of the raw benefits without the hassle.
Practically speaking, the A/D converter is always going to use a higher bit depth than the final signal path or recorder outputs. In some cases for linear raw the bit depth of the A/D converter and the record path can be equal, but for video or log output this simply doesn't make sense. The reason being is that our eyes don't perceive light in a linear fashion. In fact, the downside of linear raw is that that it allocates a tremendous portion of it's storage bits to highlights and very little to the shadows. While this can be useful in situations with extreme highlights, it's not terribly useful for recovering from the shadows. Log by comparison makes an effort to use a DSP (digital signal processor) to reallocate the linear values from A/D converter into log encoded values.
Absolutely - 16 bit raw is incredible. But when you're looking at cameras storing log and raw values at 10bits and 12bits, it really deserves a more careful look at the math. For instance, the Sony F35 has a max output of 12bit RGB 444, but it uses a 14bit A/D converter, where the RED One MX used a 12bit A/D and 12bit linear raw encoding. When you look at the math that way, and remember that the linear raw file is over half highlight information, it's a bit easier to understand why people though the F35 had more pleasing skin tones - it was using more pixels to store where the skin tones were exposed.
Of course the F35 is dated now, but I suspect it's 12bit RGB 444 will be a very competitive image against the FS7 12bit RAW.
So, in my opinion, if it's coming from a good enough A/D converter, I do think that Log gives you the majority of the raw benefits without the hassle.
