Perspective

On Jul 24, 12:28?am, "N" wrote:
If perspective has nothing to do with focal length and only relates to the
distance between the subject and camera, what makes a 50mm lens normal?

My first 35 was a Ricoh with a fixed 45 mm lens (1957), second and
still favorite was a Nikon S-2 (1958) with a "notmal" 50 MM, seems
like around 1960 the SLR was introduced shockingly with a 55 MM,
explanation given was that the extra distance was needed for the
mirror. Many favored the 85 mm for portraits as they could get more
distance from the subject thereby making noses less prominent.
My common sense take is that as the lenses became more sophisticated
the collapsable lens on the old Leicas could not be used and to keep
the camera a portable size, 50 was the compromise.
Marshel

On Jul 23, 11:28 pm, "N" wrote:
If perspective has nothing to do with focal length and only relates to the
distance between the subject and camera, what makes a 50mm lens normal?

Convention. This distance has varied, starting long ago as about 45mm
on a 35mm lens, to about 55 mm today.

Tests were done by camera and film mfgs way back to determine distance
people viewed various prints, and how they perceived perspective that
supposedly matched perspective of eye. If I remember right this was
back either before 35mm was a big thing, or about when 35 just began
to catch on- say late thirties.

"Jürgen Exner" wrote in message news:Hegpi.640$zJ4.435@trndny03...
N wrote:

If perspective has nothing to do with focal length and only relates
to the distance between the subject and camera, what makes a 50mm
lens normal?

The fact that a lens with 50mm focal length on a regular 35mm film has approximately the same angle of view as the normal human
vision.

jue

Sorry, but this is nonsense. We see in angles of a range of maybe 220
degrees to much less than one degree, depending on circumstances.
For much more on this, see my, "On Seeing and Perspective", at
http://www.donferrario.com/ruether/a...ml#perspective (which
includes a surprise for many on the true perspective type we see in,
and an example image), and, "On Lens Perspective Types", at
http://www.donferrario.com/ruether/a...spective-types,
which covers among other things FL-format relationships.
--
David Ruether

http://www.donferrario.com/ruether

N wrote:
If perspective has nothing to do with focal length and only relates to the
distance between the subject and camera, what makes a 50mm lens normal?


A good therapist?
Allen

On 2007-07-23 21:49:41 -0700, "David J. Littleboy" said:


"N" wrote:
If perspective has nothing to do with focal length and only relates to the
distance between the subject and camera, what makes a 50mm lens normal?

Nothing.

It's a hideous focal length: it's too short for isolating the subject and
it's too long to show the space and context the subject exists in.

Nonsense. It is no different than any other lens. It is simply a matter
of how far you want to stand from the subject. Many of the great
photojournalists used nothing but lenses ranging from 45mm to 55mm.

--
Waddling Eagle
World Famous Flight Instructor

Have to disagree David.

50mm on a 1.6 cropped body is spot on (as you know, close to 85mm on a full
frame body).


"David J. Littleboy" wrote in message
...

"N" wrote:
If perspective has nothing to do with focal length and only relates to
the distance between the subject and camera, what makes a 50mm lens
normal?

Nothing.

It's a hideous focal length: it's too short for isolating the subject and
it's too long to show the space and context the subject exists in.

N wrote:
If perspective has nothing to do with focal length and only relates to the
distance between the subject and camera, what makes a 50mm lens normal?

If you expose a standard 35mm frame through a 50mm lens, print a photograph and
then view it from a "normal" viewing distance (approximately the diagonal of the
print or a bit more) the angular sizes of the objects in the print will be about
the same as they were in the real life. That's what makes 50mm lens normal.

In general, in order to achieve that effect with a photograph taken with a lens
of focal length L, a print magnified M times has to be viewed from the distance
of L*M. If you accept the exact "diagonal" as the normal viewing distance and
then apply this law to the 24x36mm frame, you will easily arrive at about 45mm
as the "normal" focal length for the lens. 50mm was chosen for some
technical/historical reasons.

Andrey Tarasevich added these comments in the current discussion
du jour ...

N wrote:
If perspective has nothing to do with focal length and only
relates to the distance between the subject and camera, what
makes a 50mm lens normal?

If you expose a standard 35mm frame through a 50mm lens, print
a photograph and then view it from a "normal" viewing distance
(approximately the diagonal of the print or a bit more) the
angular sizes of the objects in the print will be about the
same as they were in the real life. That's what makes 50mm
lens normal.

In general, in order to achieve that effect with a photograph
taken with a lens of focal length L, a print magnified M times
has to be viewed from the distance of L*M. If you accept the
exact "diagonal" as the normal viewing distance and then apply
this law to the 24x36mm frame, you will easily arrive at about
45mm as the "normal" focal length for the lens. 50mm was
chosen for some technical/historical reasons.

I've never seen the analysis done quite this way, thank you. And,
I've never seen the math come out to show that "normal" is really
45mm. In my days of 35mm with a Nikon Photomic FTN, zoom lenses
weren't practical or any damn good, so I had the usual focal
length primes. Now, with a digital, I suppose I could try some
test shots and prints at 45 and 50mm equivalents, but I doubt I'd
like it.

I know portrait photographers like a mild tele, like 85mm,
because it reduces unflattering parts of the face like big ears
or a big nose. In my hobby of collecting car pictures, I find the
very same thing about cars. At car shows and museums, I can
seldom get to 85mm, but if I can back up, then I definitely will
shoot in that range because I think the proportions of the car
look more real, especially if I am shooting down low but do not
want that perspective distorted artistic look.

As to your supposition about historical or technical reasons for
the focal lengths we're all familiar with, I have no clue how
50mm was selected, but neither do I understand the 24mm and 35mm
wide angles I had for my Nikon or the 105mm telephoto. What
established those particular numbers as a standard? Who knows!
Ditto for exactly what we accept to this very day for f/stop
numbers. I understand that the peculiar looking number, to a
novice, are because each is 1/2X or 2X AREA of the aperture, but
how did the exact sequence of numbers become standard? Same
answer, I have no clue.

--
HP, aka Jerry

"Andrey Tarasevich" wrote in message
...
N wrote:
If perspective has nothing to do with focal length and only relates to
the
distance between the subject and camera, what makes a 50mm lens normal?

If you expose a standard 35mm frame through a 50mm lens, print a
photograph and
then view it from a "normal" viewing distance (approximately the diagonal
of the
print or a bit more) the angular sizes of the objects in the print will be
about
the same as they were in the real life. That's what makes 50mm lens
normal.

In general, in order to achieve that effect with a photograph taken with a
lens
of focal length L, a print magnified M times has to be viewed from the
distance
of L*M. If you accept the exact "diagonal" as the normal viewing distance
and
then apply this law to the 24x36mm frame, you will easily arrive at about
45mm
as the "normal" focal length for the lens. 50mm was chosen for some
technical/historical reasons.


If I hold a print in my hand it's going to be about 15 inches from my eyes.
That distance feels comfortable and I wouldn't want to hold it any closer
for viewing. The diagonal of a 12 x 8 inch print is about 15.49 inches, so
any tests would be best done with prints of 12 x 8 inches. Maybe that's why
I don't like viewing 6 x 4 prints.

Time to get the A3 printer out of mothballs and hope it still works.

This whole test could get screwed by my rotten eyesight but I'll see what I
can do on the weekend with photos at various focal lengths printed at the
same size.

what makes a 50mm lens normal?
You lot do overcomplicate things!
See for yourself... get your 35mm slr and 3 lenses, 1 around 28mm, 1 around
100mm and your "normal" 50mm... attach them in turn and look through the
viewfinder with right while keeping left eye open also.
When I do this I see:
28mm = right eye through viewfinder objects look smaller and further away
than left eye.
100mm = right eye through viewfinder objects look larger and closer than
left eye.
50mm = right eye through viewfinder objects look the same as left eye i.e.
"normal"
That is why it is referred to as a "normal" lens... things just look
"normal"
in size and distance.