Subject:
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Re: Math/Optics Problem
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Newsgroups:
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lugnet.off-topic.geek
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Date:
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Wed, 15 Aug 2001 20:11:07 GMT
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Viewed:
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202 times
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In lugnet.off-topic.geek, Bruce Schlickbernd writes:
> It's amazing how much physics and math I have forgotten, so let me simply
> note that the focus of the camera isn't going to change the proportions of
> the objects. The focal length will.
> [snip]
> Using a "zoom" lens allows you to change the focal length of the lens
> dynamically and thus the proportions of the closer and further objects.
Ahhh-- so perhaps I've been getting stuck on photography terminology. I had
assumed the "focus" in Shiri's response to relate to the fuzziness of the
resulting image, not the "focal length" which affects the zoom level. That
makes just about perfect sense then.
So as to the original questions:
#1 Will the fisheye constant be consistant for the same camera?
Not unless the camera has no zoom.
#2 If not, will it at least be constant for the same zoom level?
Yes-- assuming the same photo print size (as the same picture blown up will
require a different constant?).
#3 are there any other "missing pieces" to the formula?
Possibly the distance-to-lens/distance-to-image-surface factor, which may or
may not be affected by zoom, but is slightly different for each camera. And
this only affects distance from the *camera* to the object, not relative
distances, as it is canceled out, and not a multiplicative factor in the
equasion.
#4 what is the formula for figuring out the distance between the two objects?
A1 = actual height of object 1
P1 = photo height of object 1
A2 = actual height of object 2
P2 = photo height of object 2
F = fisheye constant
C = lens distance constant
Relative Distance = F*(A1/P1 - A2/P2)
#5 can I use that same formula to find out how far away from the *camera*
the objects are?
Actually, the above is derived from such a formula:
Distance from camera = F*(A1/P1) + C
And notice:
F is affected by:
- lens material
- lens concavity/convexity
- zoom level (focal distance)
- print size
C is affected by:
- focal length?
- camera internals? (distance light has to travel within camera)
- potentially by lens material & lens concavity/convexity, as it will
affect light travel distance, if such is indeed a factor
DaveE
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Message is in Reply To:
 | | Re: Math/Optics Problem
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| It's amazing how much physics and math I have forgotten, so let me simply note that the focus of the camera isn't going to change the proportions of the objects. The focal length will. The perspective will change as your lens measurement changes (in (...) (23 years ago, 14-Aug-01, to lugnet.off-topic.geek)
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