"juky" <juklingos@[EMAIL PROTECTED]
> wrote in message
news:9b19cb36-435f-4c4d-a19a-b297b95b1055@[EMAIL PROTECTED]
> Dear all,
>
> I have a mathematical question regarding relation between zoom factor
> and magnification. My digital video camera shows me the current zoom
> factor selected. Focal is 3,5-91 mm. I'm looking for mathematic
> formulas which give me the zoom factor to be selected so that an
> object in the shot will appear halved, double, etc. I premise the
> object distance is unknown.
> Is there any way?
>
> Thank you.
> Juky
If you know what a 'normal' lens focal length is for your camera, you
simply
divide the focal in question by the normal focal length, and you get the
magnification. The focal length of a 'normal' lense is basically the
diameter of a circle that would emcompass the image frame.
For a 35mm camera, 50mm is considered normal. A 28mm lens would be 0.56X.
A
300mm would be 6X. The zoom lens I was shooting with earlier, an 85-300mm
would be 1.7X to 6X. I have no idea what would be a normal focal length
lens
for your camera-- a shot in the dark guess would be 20 to 30mm or
thereabouts, but that's a guess only. The object distance would be
immaterial.
I'm assuming that you made a typo when you wrote 3 comma 5, and you meant
3
point 5. In which case, a 3.5-91mm zoom is a pretty big range. Are you
sure
that's what it says?
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