Jump to content


Photo

Log Exposure vs Linear Exposure


  • Please log in to reply
3 replies to this topic

#1 Ashim

Ashim
  • Basic Members
  • PipPip
  • 81 posts
  • Other

Posted 09 October 2006 - 11:02 AM

Could anyone kindly give me a detailed explanation on the differences between Log Exposure vs.
Linear Exposure and the way it affects Image processing.
Any help shall be valued.
  • 0

#2 Mike Brennan

Mike Brennan
  • Basic Members
  • PipPipPipPip
  • 581 posts
  • Cinematographer
  • London

Posted 09 October 2006 - 03:20 PM

Could anyone kindly give me a detailed explanation on the differences between Log Exposure vs.
Linear Exposure and the way it affects Image processing.
Any help shall be valued.


Do you mean exposing for log vs Linear
or
What is the difference between log and lin in a post environment?



Mike Brennan
  • 0

#3 Ashim

Ashim
  • Basic Members
  • PipPip
  • 81 posts
  • Other

Posted 10 October 2006 - 12:50 AM

Do you mean exposing for log vs Linear
or
What is the difference between log and lin in a post environment?
Mike Brennan



In the Post, where a commonly used file format for film scans, the Cineon or DPX format, uses 10 bits per channel, which equals 1024 levels, and linearly encodes the densities of the negative above base.
Now I fail to understand the latter part of the above statement ( and Linearly encodes the densities...).

I'd also like to know what does it mean to say that the Viper Filmsteream camera delivers an RGB 4:4:4
10 bit LOG output uncompromised by electronic camera processing.
Again the query is directed toward the Log output.

I underastand that film is a Log-Log medium(Log exposure vs. log density).
But what aout the digital cameras. they seem to be operating in both.

What is exposing for Log vs. Linear??
  • 0

#4 Matt Sandstrom

Matt Sandstrom
  • Basic Members
  • PipPipPipPip
  • 464 posts
  • Director
  • Stockholm, Sweden

Posted 15 October 2006 - 08:37 AM

I fail to understand the latter part of the above statement ( and Linearly encodes the densities...).

linear means that double the density means double the value. log means that double density means that the value increases by one. but i guess you knew that. i believe that ccd's are linear so if you record light, which is a log entity since it requires a doubling to get a linear increase in brightness, you get a log signal. the dsp converts this to a linear scale using a gamma of your choice.

/matt
  • 0


The Slider

Abel Cine

Metropolis Post

CineTape

Wooden Camera

FJS International, LLC

CineLab

Paralinx LLC

Willys Widgets

Ritter Battery

Rig Wheels Passport

Tai Audio

Aerial Filmworks

Opal

Media Blackout - Custom Cables and AKS

Visual Products

Broadcast Solutions Inc

Glidecam

rebotnix Technologies

Gamma Ray Digital Inc

Technodolly

rebotnix Technologies

Wooden Camera

Opal

Aerial Filmworks

Willys Widgets

FJS International, LLC

Visual Products

Broadcast Solutions Inc

Rig Wheels Passport

Gamma Ray Digital Inc

Glidecam

CineLab

The Slider

Metropolis Post

Ritter Battery

Abel Cine

Technodolly

CineTape

Media Blackout - Custom Cables and AKS

Paralinx LLC

Tai Audio