<p>When working with log profiles, the raw data from the sensor is adjusted through a process that preserves dynamic range, rather than just being a simple linear-to-log conversion. They should focus on how LUTs (Look-Up Tables) are used to map the data into a log space, which keeps highlight and shadow details intact for later grading. You can also suggest they explore specific tutorials on how log profiles are used in post-production color grading to see how this transformation works in practice.</p>

CC BY-SA 4.0
2024-11-27T23:06:12.187Z
2024-11-27T23:06:12.187Z
JMR
<p>I understand the advantage of using log profiles and how one would edit video with such a profile. But what is actually done to create a video with a log profile, given that the camera sensor elements are linear with respect to light level?</p>
<p>It would seem that either the analog output of the sensor is modified in a nonlinear way or the digital values are adjusted with a logarithmic lookup table. I doubt the former but don't get how the latter would avoid clipping already in the numbers.</p>

CC BY-SA 4.0
2024-11-27T14:23:55.433Z
It is a mix. Sensors are "linear" (but ISO, etc.), but not 8-bits (we are still analogue). Reading means to have a ADC, and you "hardcode" the logic there, and only later you have numbers (so possible "clipping").
Giacomo Catenazzi
CC BY-SA 4.0
2024-11-27T14:53:23.130Z
OETF Optical Electric Transfer Function
Jason Conrad
CC BY-SA 4.0
2024-11-29T01:15:04.860Z
@GiacomoCatenazzi  So if I understand you are saying that my first guess, which I had erroneously discounted, was the correct one - the linear analog output of the sensor is modified in some nonlinear way prior to the analog to digital conversion. That makes sense.
Not_Einstein
CC BY-SA 4.0
2024-11-29T08:02:24.967Z
Maybe. I think it is built directly in ADC chip (selectable resistors). ADC is not necessarily linear: it depends on each resistance you put it in it for each output level, so I would assume a simple logic will select few alternate resistance sets and you get different responses. Also it this stage (or nearby stages) you can do it in a parallel way (and fast).
Giacomo Catenazzi
<encoding>
How is log profile video produced?
Not_Einstein
# How is log profile video produced?

(Asked by: username_0 on 2024-11-27)

I understand the advantage of using log profiles and how one would edit video with such a profile. But what is actually done to create a video with a log profile, given that the camera sensor elements are linear with respect to light level?

It would seem that either the analog output of the sensor is modified in a nonlinear way or the digital values are adjusted with a logarithmic lookup table. I doubt the former but don't get how the latter would avoid clipping already in the numbers.

**Tags:** encoding

> **Comments:**
> **username_1**: It is a mix. Sensors are "linear" (but ISO, etc.), but not 8-bits (we are still analogue). Reading means to have a ADC, and you "hardcode" the logic there, and only later you have numbers (so possible "clipping").  
> **username_2**: OETF Optical Electric Transfer Function  
> **username_0**: @GiacomoCatenazzi  So if I understand you are saying that my first guess, which I had erroneously discounted, was the correct one - the linear analog output of the sensor is modified in some nonlinear way prior to the analog to digital conversion. That makes sense.  
> **username_1**: Maybe. I think it is built directly in ADC chip (selectable resistors). ADC is not necessarily linear: it depends on each resistance you put it in it for each output level, so I would assume a simple logic will select few alternate resistance sets and you get different responses. Also it this stage (or nearby stages) you can do it in a parallel way (and fast).  

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## 1 answers

### Answer by username_3 on 2024-11-27. Score: 0

When working with log profiles, the raw data from the sensor is adjusted through a process that preserves dynamic range, rather than just being a simple linear-to-log conversion. They should focus on how LUTs (Look-Up Tables) are used to map the data into a log space, which keeps highlight and shadow details intact for later grading. You can also suggest they explore specific tutorials on how log profiles are used in post-production color grading to see how this transformation works in practice.


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