Jump to content


Photo

What is an "Optical Low Pass Filter"


  • Please log in to reply
1 reply to this topic

#1 Carl Brighton

Carl Brighton
  • Basic Members
  • PipPipPip
  • 222 posts
  • 1st Assistant Camera

Posted 29 December 2006 - 05:40 AM

I've read that all video and digital still cameras have a thing called an "optical low pass filter" fitted to the sensor chips. The effect of this is supposedly like putting a sheet of tracing paper over the sensor.
Can anybody tell me what this actually for, and will the camera work without it?
  • 0

#2 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19769 posts
  • Cinematographer
  • Los Angeles

Posted 29 December 2006 - 12:39 PM

When fine edges and lines of a photographic subject hit the fine grid pattern of the sensor photosites, you get a phenomenon called "aliasing" -- moire-patterning and "twitter" along the edges. The solution has generally been to slightly diffuse the image before it hits the sensor to reduce the aliasing artifacts, hence why the low-pass optical filter is also called an anti-aliasing filter. I assume the higher the resolution of the camera, the more detail it can handle before aliasing, and the less-strong the low-pass optical filter is.

http://en.wikipedia....aliasing_filter

Film doesn't have a rigid grid of photosites, it has random pattern of silver halide grains, so it does not have this problem (until you transfer film to video...)
  • 0


Broadcast Solutions Inc

Metropolis Post

Technodolly

The Slider

Wooden Camera

Paralinx LLC

Abel Cine

rebotnix Technologies

Opal

CineLab

CineTape

Visual Products

Aerial Filmworks

FJS International, LLC

Glidecam

Media Blackout - Custom Cables and AKS

Gamma Ray Digital Inc

Tai Audio

Willys Widgets

Ritter Battery

Rig Wheels Passport

Visual Products

Tai Audio

Broadcast Solutions Inc

Paralinx LLC

Wooden Camera

CineLab

FJS International, LLC

Gamma Ray Digital Inc

Aerial Filmworks

Abel Cine

Media Blackout - Custom Cables and AKS

Glidecam

Willys Widgets

rebotnix Technologies

Technodolly

CineTape

Ritter Battery

Metropolis Post

Rig Wheels Passport

Opal

The Slider