Does the sensor size affect perspective, as it does with DoF ?

Started 1 week ago | Discussions thread
Tom Axford Veteran Member • Posts: 5,652
Re: [OP RESOVLED] Does the sensor size affect perspective, as it does with DoF ?

Kumsa wrote:

Tom, I'm reading the wikipedia article differently. As for the binocular and telescope, the sensor size of my eye hasn't changed, so it's not really specific to sensor size. And, do I think the perspective looks the same ? Yes, it does, in fact the perspective looks the same for the subject in the image. I'm not a birder or an astrophotographer, so my subjects are within the 14-400mm range. It's easy to validate, and I've actually done it myself.

One of the great benefits of these discussions is that it allows me to rephrase and ask better questions. So, based on this thread content, I did more searching, and found a useful article on Sensor Size, Perspective and Depth of Field. Here's the salient point: "...two cameras with different size sensors need to be at the same distance from their subjects in order to create photographs with a similar perspective." And, best of all, an example is provided.

The subject of the image holds the same perspective between sensor dimensions. The background, of course, does not.

Most of that article looks sound, except for the section on Perspective.

It is certainly true that if you take two photos from exactly the same position (and with the cameras pointing in the same direction), but with different sensor sizes and/or different focal lengths, then the relative sizes and positions of everything in the scene will look  exactly the same.  One of the images will just look like a crop from the other.  If you define perspective as meaning just the relative sizes and positions of objects, then the perspective remains the same.

However, the idea of wide-angle distortion and telephoto compression are not just figments of someone's imagination, and these are normally attributed to the perspective.

Consider these two images from the Wikipedia article on perspective distortion :

Any experienced photographer can see immediately that one is taken with a wide-angle lens and the other is taken with a telephoto lens.  These perspective effects are real.  Of course, the telephoto image may have been obtained by taking a small crop from the centre of a much larger image taken with a much shorter focal length.  That is indeed equivalent to using a longer focal length (except that a lot of resolution is lost).

The wide-angle appearance of the first image is because the camera's angle of view was much greater than our angle of view in viewing the image.  If the image was blown up very large and then viewed from very close (in this case, from a distance of about half the width of the image), then the perspective would appear quite normal.

Try it for yourself if you don't believe me!

Similarly, the compression effect visible in the second image is because the camera's angle of view was much smaller than our angle of view in viewing the image.   If you stand well back from the image when you look at it, the compression effect disappears.   It is not so easy to convince yourself of this because when you stand well back, the image looks very small and it is hard to imagine exactly how the image would look in its surroundings.  However, if you can see a normal view of the same scene, then it is a bit easier to see that the effect is solely due to angle of view of the camera relative to angle of view of the viewer.

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