Field of view/vision

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Field of view/vision

Post by Phil White » Wed Jan 26, 2005 6:25 pm

Any photographers/machine vision developers out there who can give me a precise definition of these two? The exact sector I'm interested in is machine vision. I have a couple of ideas and leads which indicate that there is a difference, but I need confirmation. I'll keep my mouth shut until some others have had a go!
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Field of view/vision

Post by Nimo Piquter » Fri Jan 28, 2005 12:56 pm

Because "Field of view" and "Field of vision" are inter-related concepts, they are often used indiscriminately.

Every camera lens, telescope etc. has a certain "field of view", which is the area that can be seen when looking through the apparatus. It is sometimes measured as the lateral distance which can be observed at a given distance from the optical instrument, or as an angle of view.

"Field of vision" is a similar concept, but more exclusionary: its referent must have vision. It can be used when referring to a person, an animal, or the eye itself.

If there is a "field of vision", there is also a "field of view"; but the converse is not necessarily true.
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Field of view/vision

Post by Phil White » Fri Jan 28, 2005 1:55 pm

Hmmmm!
Looking at several hundred websites on optics, I came to a different conclusion, namely that the "field of view" is defined in terms of an angle, and the field of vision is what you describe above: "the lateral distance which can be observed at a given distance from the optical instrument". There are a number of sites on the Web that consistently specify the field of view of, for instance, a pair of binoculars in terms of an angle and the field of vision in terms of a measured distance (e.g. http://www.monkoptics.co.uk/general.html). I was hoping someone would tell me that this (very common) distinction is correct.

On the other hand, many sites seem to mix the terms indiscriminately, e.g.
Field of view
The field taken in by a given lens. Different lenses have different fields of view - some can “see” more than others. Wide-angle lenses take in huge areas of a scene, often more than the human eye can at a time. Telephoto lenses work like telescopes - they narrow down the field of vision considerably so you can take a photograph of a distant object.

The field of view of a lens is determined by its focal length. It’s usually indicated by its angle of view, which is often measured as the diagonal of the image area.
http://photonotes.org/cgi-bin/entry.pl?id=Fieldofview

But I'm not an expert in optics.
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Field of view/vision

Post by russcable » Fri Jan 28, 2005 5:39 pm

IANAL but... "Field of view" is an objective measurement of the properties of the lens/instrument usually expressed as a single angle. "Field of vision" is a subjective and/or qualitative measurement of the usable part of the field of view (and to amplify Nimo's statement therefore requires a "viewer" whether it be an eye, a photographic plate, or an electronic light sensor). If you put an attachment on a camera for taking pictures of solar flares, the field of vision is blocked in the center. In low light conditions, the edges of the field of view may not pick up enough light for the sensor to use them. In wide angle lens, objects at the outside of the field of view may not be "interpretable" by the viewer due to distortion. With the lens cap on, there is zero field of vision, while the field of view is still the same. Et cetera.
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Field of view/vision

Post by Phil White » Sat Jan 29, 2005 12:26 am

Thanks for your help, both of you. I'm actually trying to solve a translation problem relating to a machine vision system, where the objects being analyzed are or are not located in the field of view/vision. The German term appears to be the same for both meanings you both suggest above. In context, the "field of view/vision" is always expressed in terms of the dimensions of the rectangle on the monitor on which the image is displayed, and not actually in terms of a property of the camera used, so I'm still a little uncertain as to which would be more accurate.

A message to the effect that "The component is larger than the field of view" would seem wrong to me from what you have said and from what I said above, namely that the field of view is usually expressed as an angle and the field of vision is usually expressed as a dimension or area.
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Field of view/vision

Post by Erik_Kowal » Sat Jan 29, 2005 1:16 am

Your explanation suggests the most accurate translation is "The size of the component exceeds that of the field of vision".
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Field of view/vision

Post by Nimo Piquter » Sat Jan 29, 2005 1:20 am

If the only difference were the way in which the field is quantified (i.e. angle or distance), then "field of view" and "field of vision" would be identical concepts, differing only in the mode of measurement. Furthermore, the two modes of measurement ultimately give us the same information, as either one can be derived from the other.

It is surprisingly difficult to find any authoritative source which clearly contrasts the two terms.

Here are two definitions from the same source which (sort of) support the distinction I made:

field of view
n : the area that is visible (as through an optical instrument)

field of vision
n : all of the points of the physical environment that can be perceived by a stable eye at a given moment [syn: visual field, field of regard]

Source: WordNet ® 2.0, © 2003 Princeton University
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