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aperture angle

 
 
logiclips@yahoo.com
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      05-29-2005
Hi,

How can I obtain the aperture angle (in degrees) of a camera when I
have the aperture (e.g. f/3.2) and the focal length?

BTW: What is the meaning of this spec?
Focal Length: 4.5mm (35mm equivalent 37mm)


Thanks in advance...

Peter

 
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Jim
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      05-29-2005

<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
> Hi,
>
> How can I obtain the aperture angle (in degrees) of a camera when I
> have the aperture (e.g. f/3.2) and the focal length?

You also need the sensor size, but the aperature is not needed. After that,
it is a matter of trigonometry.
>
> BTW: What is the meaning of this spec?
> Focal Length: 4.5mm (35mm equivalent 37mm)

The actual focal length is 4.5mm. The angle of view corresponds to that of
a 37mm lens on a 35mm image (which is 24x36 mm).
Jim


 
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David J Taylor
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      05-29-2005
Jim wrote:
> <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) oups.com...
>> Hi,
>>
>> How can I obtain the aperture angle (in degrees) of a camera when I
>> have the aperture (e.g. f/3.2) and the focal length?

> You also need the sensor size, but the aperature is not needed.
> After that, it is a matter of trigonometry.
>>
>> BTW: What is the meaning of this spec?
>> Focal Length: 4.5mm (35mm equivalent 37mm)

> The actual focal length is 4.5mm. The angle of view corresponds to
> that of a 37mm lens on a 35mm image (which is 24x36 mm).
> Jim


Except that the sensor is (most likely) 4:3 aspect ratio rather than 3:2
aspect ratio...

David


 
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logiclips@yahoo.com
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      05-29-2005
The sensor has a max resolution of 1280 x 960 (1.3 Mio). Is it possible
to get the sensor size of this information or can I work with 37mm lens
and 24x36 mm image?
Furthermore I'm a little bit confused: The aperture angle depends on
the aperture size, isn't it?

Thanks,

Peter

 
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David J Taylor
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      05-29-2005
http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:
> The sensor has a max resolution of 1280 x 960 (1.3 Mio). Is it
> possible to get the sensor size of this information or can I work
> with 37mm lens and 24x36 mm image?
> Furthermore I'm a little bit confused: The aperture angle depends on
> the aperture size, isn't it?


Sensor sizes are described here:

http://www.dpreview.com/learn/?/Glos...r_Sizes_01.htm

Find out which of these is in your camera.

I would not use the term "aperture angle", it means nothing to me. You
can talk about focal length, field of view, and f/number.

David


 
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ASAAR
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      05-29-2005
On 29 May 2005 09:00:27 -0700, (E-Mail Removed) wrote:

> BTW: What is the meaning of this spec?
> Focal Length: 4.5mm (35mm equivalent 37mm)


It means that the size of the sensor in the camera with the 4.5mm
lens is far smaller than the size of the film frame in the 35mm
camera. If both lenses (37mm and 4.5mm) could be fitted to the same
35mm camera (assuming that the 4.5mm lens could fill the frame,
which it probably couldn't), the 4.5mm would resemble a super-wide
lens. If a picture of an object was taken (at the same distance)
with both cameras and the film was developed, you could hack at the
negative produced by the 4.5mm with a pair of scissors. If you cut
out a rectangular piece of film that shows the same image that is
contained in the full frame taken by the 37mm lens, that small
rectangular piece you cut out would be the size of the sensor in the
camera using the 4.5mm lens. In other words, with that camera, a
4.5mm lens is equivalent to a 37mm lens in a 35mm camera, because
uncropped prints from both would show approximately the same image.

 
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Joseph Meehan
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      05-29-2005
(E-Mail Removed) wrote:
> Hi,
>
> How can I obtain the aperture angle (in degrees) of a camera when I
> have the aperture (e.g. f/3.2) and the focal length?
>
> BTW: What is the meaning of this spec?
> Focal Length: 4.5mm (35mm equivalent 37mm)
>
>
> Thanks in advance...
>
> Peter


What is an "aperture angle?" I have never heard the term and I can't
imagine what it refers to.


--
Joseph Meehan

Dia duit


 
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Gisle Hannemyr
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      05-29-2005
(E-Mail Removed) writes:

> The sensor has a max resolution of 1280 x 960 (1.3 Mio). Is it
> possible to get the sensor size of this information [...] ?


No, this is no use in computing the physical area of the sensor

But earlier, you wrote:

>>> Focal Length: 4.5mm (35mm equivalent 37mm)


This is the data you need to compute sensor size. By dividing 37 by
4.5, we find a crop factor equal to 8.2 - so the diameter of your
camera's sensor is 5.3 mm - which means the imager's dimensions is
something like 4.24 mm x 3.18 mm.

> Furthermore I'm a little bit confused: The aperture angle depends on
> the aperture size, isn't it?


I've never heard the term "aperture angle", so I am not sure what sort
of formula this would be.

But if you want to know the angle "seen" by your camera's - that
particular datum is usually called "field of view" (FOV) and depends
on focal length and sensor diameter (but not on aperture). You'll
find the formula explained on this webpage:
http://folk.uio.no/gisle/photo/crop.html

For your camera, the FOV a f=4.5mm is atan(5.3/2/4.5), which is
1.064 radians or ~ 61 degrees. It is the same FOV that a lens
with f=35mm lens would have with a 24x36 mm imager.
--
- gisle hannemyr [ gisle{at}hannemyr.no - http://folk.uio.no/gisle/ ]
------------------------------------------------------------------------
Kodak DCS460, Canon Powershot G5, Olympus 2020Z
------------------------------------------------------------------------
 
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Neil Ellwood
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      05-29-2005
(E-Mail Removed) wrote:

>
> BTW: What is the meaning of this spec?
> Focal Length: 4.5mm (35mm equivalent 37mm)


Exactly what it says. The focal length of the lens is 4.5mm which is
the equivalent to a 35mm camera with a lens of 37mm.
--
neil
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Neil Ellwood
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      05-29-2005
Joseph Meehan wrote:

>
> What is an "aperture angle?" I have never heard the term and I
> can't
> imagine what it refers to.
>
>

Don't tell him but there is no such animal.....
--
neil
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