Larger formats have less perspective distortion: My Theory.

Started Oct 9, 2013 | Discussions thread
Mattoid
Regular MemberPosts: 254
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Re: Larger formats have less perspective distortion: My Theory.
In reply to John1940, Oct 10, 2013

John1940 wrote:

Mattoid wrote:

Firstly, I am fully aware that the only thing that changes perspective is your position relative to the subject. I have myself corrected people who erroneously state that different focal lengths change the perspective.

However I have a nagging feeling that format does have something else on the overall rendering of the image, beyond the common accepted advantages like dynamic range etc.

Although it may be small, I do think that larger formats exhibit less perspective distortion at the same angle of view.

For a hypothetical comparison, let’s pretend that all lenses have zero barrel or pincushion distortion. Lets also pretend that we have complete control over the light of the scene so we can have the exact same depth of field (basically everything in focus) and we crush the highlights and shadows of the larger format to give the same dynamic range. Everything else is equivalent and can be forgotten.

I will compare a 35mm “full frame” sensor (36*24mm) with a 1/ 2.3 “compact” sensor (6.17*4.55mm). because they are different aspects let’s just look at the vertical. Each sensor is supplied with an appropriate lens to give a vertical angle of view of say 60 degrees.

If we set the two cameras up in a room were the centre of each sensor is exactly 100cm high off the floor. So the light from the subject is taking the exact same path to get to the centre of each sensor.

But the top of the full frame sensor is at 101.2 cm and the top of the compact sensor is at 100.2275cm. Almost a cm difference. The light from the subject is coming from different angles to the sensor at this part of the image. E.g. if the subject is a 1cm high cube with its centre also at 100cm height, the top of the compact sensor will be looking slightly up at the top edge of the cube, but the top of the full frame sensor will be looking slightly down at the top edge of the cube. Dismissing some weird lens arrangement that bends the light, I can’t see how this wouldn’t have an effect on the rendering of the image.

The difference may be small but surely it exists?

The difference becomes even more apparent if you think of a large format film with a height of 5 inches. The light from any particular peripheral point has to be bent less. And if we take things to extremes and imagine that we remove one wall from a room and put a piece of film 10 feet high, it becomes easier to imagine the type of change this would have on the image and makes it seem impossible that format size DOSENT have an effect on perspective distortion.

I would love to hear peoples thoughts on this.

See the following

http://en.wikipedia.org/wiki/Perspective_distortion_(photography)

John1940

I have seen that already several years ago, but thanks for the link.

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