Alley in Pisa, Italy

by Lars Kotthoff

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I've never heard of the system that was described in the question but I can understand how it works. I can see no reason that it wouldn't work for fixed image photography as it would for cinematography. What concerns me is the quality. The large lens, ground glass (possibly milk glass), and the attachment to the camera lens would all have to be light tight. ...


The "telecompressor" you mentioned is a focal reducer, a device that concentrates the image in order to project it onto a smaller sensor. This approach reduces the backfocus distance (the distance from the back of the lens to the sensor). So it only works on mirrorless cameras using lenses designed for DSLRs (which have sufficient backfocus distance to make ...


This is not "obviously irrelevant to normal photography" at all; we just don't normally worry about the sort of precision that you'll need to deal with. There are two numbers that we ordinarily take at face value, knowing that they're slight fibs: the focal length of the lens (which is usualy rounded to a "friendly" value except on data sheets), and the ...


The answers above are correct but another way of looking at it is as mentioned: all lenses create a circular image. Most are designed so that the diameter of the image circle is greater than the diagonal of the sensor otherwise you are not filling the whole sensor. Now fish eye lenses are designed to cover 180 degrees in all directions so to make the whole ...


Your second diagram is exactly on point here. Or at least it is for traditional lenses (that is, lenses that are not internal focus). All you need to do is scale the diagram's width according to the focal length of the lens. Longer focal lengths mean that you are focusing closer (at distances less than infinity); that is, the distance between the lens and ...


All lenses create a circular image, it's just that most of them have an image circle large enough that it covers the entire sensor. Vignetting at wide apertures is a manifestation of the image circle encroaching on the corners of the sensor as the circle edge is not as sharp as it would be with a narrower aperture. With a fish-eye lens, the image circle is ...


Consider this review of the Canon 8-15 f/4L USM fisheye, which can shift from circular at 8mm to diagonal at 15mm. Yes, it's circular because the lens's entire image circle is inside the area of the sensor, rather than covering the entire sensor. I'm not sure there's going to be an entire explanatory webpage other than Wikipedia on this, because it's such a ...

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