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On Wed, 15 Dec 2010 00:27:36 +0100, Alfred Molon wrote:

> Why is a 50mm lens "normal" (in a full frame camera)? Because it
> corresponds to the usual angle of view of the human eye, or just because
> this focal length lies in the middle between wide and tele?

Could be wrong, but as I understand - it's because the diagonal of 35 mm
film is pretty close to 50mm.

On 15 Dec 2010 00:57:42 GMT, ray <> wrote:

>On Wed, 15 Dec 2010 00:27:36 +0100, Alfred Molon wrote:
>
>> Why is a 50mm lens "normal" (in a full frame camera)? Because it
>> corresponds to the usual angle of view of the human eye, or just because
>> this focal length lies in the middle between wide and tele?
>
>Could be wrong, but as I understand - it's because the diagonal of 35 mm
>film is pretty close to 50mm.

The diagonal of 35mm film is 45.79mm.



Eric Stevens

On Wed, 15 Dec 2010 14:04:22 +1300, Eric Stevens <>
wrote:
: On 15 Dec 2010 00:57:42 GMT, ray <> wrote:
:
: >On Wed, 15 Dec 2010 00:27:36 +0100, Alfred Molon wrote:
: >
: >> Why is a 50mm lens "normal" (in a full frame camera)? Because it
: >> corresponds to the usual angle of view of the human eye, or just because
: >> this focal length lies in the middle between wide and tele?
: >
: >Could be wrong, but as I understand - it's because the diagonal of 35 mm
: >film is pretty close to 50mm.
:
: The diagonal of 35mm film is 45.79mm.

Is it? I get about 43.27mm. The frame size is 24 x 36 mm, right?

Bob

"Robert Coe" <> wrote in message
news:...
> On Wed, 15 Dec 2010 14:04:22 +1300, Eric Stevens
> <>
> wrote:
> : On 15 Dec 2010 00:57:42 GMT, ray <> wrote:
> :
> : >On Wed, 15 Dec 2010 00:27:36 +0100, Alfred Molon wrote:
> : >
> : >> Why is a 50mm lens "normal" (in a full frame camera)? Because it
> : >> corresponds to the usual angle of view of the human eye, or just
> because
> : >> this focal length lies in the middle between wide and tele?
> : >
> : >Could be wrong, but as I understand - it's because the diagonal of 35
> mm
> : >film is pretty close to 50mm.
> :
> : The diagonal of 35mm film is 45.79mm.
>
> Is it? I get about 43.27mm. The frame size is 24 x 36 mm, right?
>
> Bob

Agreed on 43.27 mm

David

On Tue, 14 Dec 2010 22:48:47 -0500, Robert Coe <> wrote:

>On Wed, 15 Dec 2010 14:04:22 +1300, Eric Stevens <>
>wrote:
>: On 15 Dec 2010 00:57:42 GMT, ray <> wrote:
>:
>: >On Wed, 15 Dec 2010 00:27:36 +0100, Alfred Molon wrote:
>: >
>: >> Why is a 50mm lens "normal" (in a full frame camera)? Because it
>: >> corresponds to the usual angle of view of the human eye, or just because
>: >> this focal length lies in the middle between wide and tele?
>: >
>: >Could be wrong, but as I understand - it's because the diagonal of 35 mm
>: >film is pretty close to 50mm.
>:
>: The diagonal of 35mm film is 45.79mm.
>
>Is it? I get about 43.27mm. The frame size is 24 x 36 mm, right?
>

I thought it was 1" x 1.5" derived from two of the original 35mm film
size of 1" x 3/4".



Eric Stevens

On Tue, 14 Dec 2010 22:48:47 -0500, Robert Coe <> wrote:

>On Wed, 15 Dec 2010 14:04:22 +1300, Eric Stevens <>
>wrote:
>: On 15 Dec 2010 00:57:42 GMT, ray <> wrote:
>:
>: >On Wed, 15 Dec 2010 00:27:36 +0100, Alfred Molon wrote:
>: >
>: >> Why is a 50mm lens "normal" (in a full frame camera)? Because it
>: >> corresponds to the usual angle of view of the human eye, or just because
>: >> this focal length lies in the middle between wide and tele?
>: >
>: >Could be wrong, but as I understand - it's because the diagonal of 35 mm
>: >film is pretty close to 50mm.
>:
>: The diagonal of 35mm film is 45.79mm.
>
>Is it? I get about 43.27mm. The frame size is 24 x 36 mm, right?
>

I've just done a terrible thing. I've actually _measured_ the
negatives produced by my old Nikon F801s. I find they are 37.15mm x
24.15mm, which gives a diagonal of 44.31mm. Having said that, I will
confess that hand-held caliper measurements of images on plastic are
not the most precise and the actual dimensions might be slightly
different.

The pitch of the images depends on the sprocket holes which I measure
as 1.5" or 38.1mm. I believe that is a long-standing standard
dimension.



Eric Stevens

On Wed, 15 Dec 2010 14:04:22 +1300, Eric Stevens wrote:

> On 15 Dec 2010 00:57:42 GMT, ray <> wrote:
>
>>On Wed, 15 Dec 2010 00:27:36 +0100, Alfred Molon wrote:
>>
>>> Why is a 50mm lens "normal" (in a full frame camera)? Because it
>>> corresponds to the usual angle of view of the human eye, or just
>>> because this focal length lies in the middle between wide and tele?
>>
>>Could be wrong, but as I understand - it's because the diagonal of 35 mm
>>film is pretty close to 50mm.
>
> The diagonal of 35mm film is 45.79mm.

As I indicated: pretty close - not exact.


>
>
>
> Eric Stevens