Bob,
I don't but you can fairly easily compute the angle of view of most lenses
using the "formula" that is described in the PhotoForum FAQ pages where you'll
find answers to several (hundreds??) esoteric questions! Find the "index" page
at http://www.rit.edu/~andpph/pf-faq.html
Of course this assumes you know what the sensor size is (unless you are shoting
film in a 35mm camera and then the "sensor" dimension is 24 x 36 mm! ;) andy
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Note 15.02 -< What is Angle of View of any Lens on any Camera? >-
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I'd like to know whether there exists a formula (or second best, a conversion
table) for calculating the angle of view given a focal length, and vice versa
(e.g. given a 300mm lens, 8.1 degrees is correct....I think)
The formula is:
The angle of view for any given film dimension is equal to 2 times the angle
whose tangent is equal to the film dimension in question divided by 2 times the
focal length.
this is for a non-distorting lens that is a "regular" lens not a fisheye.
-1 / film dimension\ 43
let's see < of view = < tan |---------------| -------- = .071
\ 2 f / 2 x 300
angle whose tan = .071 = 4.09 x 2 = 8.18
pretty close, eh?
BTW, 35 mm format dimensions are 24mm x 36mm and the diagonal is 43mm (or 44).
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For a hypothetical solid state sensor with a diagonal measurement of 25 mm
the situation in the cases you mentioned would be like this:
25 divided by (2 times 17) or 34 = .074 and whose inv tan values is: 36.33
degrees or a total angle of view of twice that which is 73 degrees.
25 divided by 100 (2 times 50) or 100 = .25 and whose inv tan value is:
14.04 or a total angle of view twice that which is 28 degrees.
Now you take a protractor and draw out these angles and you can visualize
their angles of view in graphical form. If we assume the sensor size is as I
mentioned above then it can be clearly seen that the 17 mm setting on the
17-40 zoom covers about two and a half times the angle of view of the other
lens at the 50 mm setting.
I think the above could be simplified but I decided to take the info just as
it is listed on the FAQ page at: http://www.rit.edu/~andpph/pf-faq/faq-15.html
I hope this is right ... it is late here and my eyes are tired!
cheerio,
andy
Bob wrote:
Does anyone know of a web site that has examples of the angle of view of
different lenses? My wife and I are doing a thing for one of our sons
and we were getting shots the other day and she was wondering why I was
changing lenses now and then.
I can get closest focus info from Canon's site but I haven't been able
to find examples of my 17-40 @ 17mm vs my 28-70 @ 50mm.
Thanks.....
Bob
