Dem Bell

Lives in United Kingdom United Kingdom
Works as a Research Analyst
Joined on Apr 11, 2018

Comments

Total: 5, showing: 1 – 5
In reply to:

Jonsi: Title says perspective distortion.
Video says perspective compression.

It is compression.

Wikipedia says "compression distortion"...

Link | Posted on Jun 5, 2018 at 22:00 UTC

It doesn't really help to replace a term "lens compression" with "perspective distortion" without ever explaining what these terms are.

It would have been better to start with the fact that photographs are usually viewed from a distance that is roughly the diagonal of the image. If you shoot with a standard lens (or crop a wide angle shot to standard FOV, or do a panorama with a telephoto lens to fill the standard FOV, does not matter) then the image perspective will look normal from a typical viewing distance.

Wider or telephoto lenses are going to produce perspective that doesn't match the typical viewing distance - the perspective is going to look distorted. That is "perspective distortion", "compression distortion" in the case of a telephoto lens. Call it "lens compression" if you want. There is no drama.

Link | Posted on Jun 3, 2018 at 22:01 UTC as 8th comment
In reply to:

barringtonpro1: (Peter Cockerell) agreed / Reality is perception. I perceive compression.

A term "compression" implies the existence of two states: normal and compressed. I perceive compression when wearing shoes that are a size too small. Here we have a clear reference point and the shoes that are a bit short of it, thus causing compression.

When people say that compression refers to the shortening of the distance between the foreground and the background, my only question to them is: "Compared to WHAT?"

Link | Posted on Jun 1, 2018 at 18:57 UTC
In reply to:

dbm305: Another semantic point, but perspective distortion is just as bad a term. It’s not distortion, it’s how things sort of look from those perspectives, and exactly how they look projected to a two dimensional surface preserving straight lines. “Perspective effect” might be better...

That is called "perspective". Perspective of a photograph is not distorted only if you are viewing it from the same angle that it was recorded. If your viewing position is different, you get "perspective distortion".

Link | Posted on May 31, 2018 at 16:36 UTC
In reply to:

TsubasaOfficial: You should avoid using the word "distortion". It's just perspective.
Because if you say so, people will mess this word up with the barrel/pincushion distortions.

"Compression distortion" is the flat appearance of the image when it is viewed from an angle wider than the narrow angle of view used to create the image (either by cropping or by using a telephoto lens).

Equally, if you are viewing a wide angle shot from a normal viewing distance, the perpective will appear exaturated (known in literature as "extension distortion"). But if you stick your nose to the same image, the perpective will look right.

The author simply doesn't understand the difference between "perspective" = point of view of the camera and "perspective distortion" = is the viewer's perpective different from that of the camera?

I have not come across a book that defines "lens compression".

Link | Posted on May 31, 2018 at 16:07 UTC
Total: 5, showing: 1 – 5