Answers.Body: <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>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-11-27T23:06:12.187Z
Answers.LastActivityDate: 2024-11-27T23:06:12.187Z
Answers.UserDisplayName: JMR
Body: <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>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-11-27T14:23:55.433Z
Comments.Text: 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").
Comments.UserDisplayName: Giacomo Catenazzi
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-11-27T14:53:23.130Z
Comments.Text: OETF Optical Electric Transfer Function
Comments.UserDisplayName: Jason Conrad
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-11-29T01:15:04.860Z
Comments.Text: @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.
Comments.UserDisplayName: Not_Einstein
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-11-29T08:02:24.967Z
Comments.Text: 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).
Comments.UserDisplayName: Giacomo Catenazzi
Tags: <encoding>
Title: How is log profile video produced?
UserDisplayName: Not_Einstein
ThreadText: # 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**: @username_1  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).  
  
  ---
  
  ## 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.
  
  
  ---
  
  