Perspective

Discussion in 'Digital Photography' started by N, Jul 24, 2007.

  1. N

    N Guest

    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?
     
    N, Jul 24, 2007
    #1
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  2. "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.

    It became "normal" by default. In the day of fixed lens cameras. 110mm on
    6x9, 75 or 80mm on 6x6, or 50mm on 35mm have the property that they are the
    shortest (widest) lens that can be made with a simple lens design (although
    they are retrofocus on an SLR). Anything wider would require more expensive
    optics and anything longer would make a larger and less useful for snapshots
    camera.

    A 50mm lens on a 6x6 or 6x7 camera, on the other hand, is a lovely focal
    length.

    David J. Littleboy
    Tokyo, Japan
     
    David J. Littleboy, Jul 24, 2007
    #2
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  3. 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
     
    Jürgen Exner, Jul 24, 2007
    #3
  4. N

    N Guest

    "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
    >


    Does your eye have an angle of view of 46 degrees? Mine is certainly wider
    than that.
     
    N, Jul 24, 2007
    #4
  5. N wrote:
    > "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.

    >
    > Does your eye have an angle of view of 46 degrees? Mine is certainly
    > wider than that.


    Certainly. But you don't really 'see' with your peripheral vision. The area
    that you _conciously_ see and focus on is approximately equivalent to the
    50mm angle of view.

    jue
     
    Jürgen Exner, Jul 24, 2007
    #5
  6. N

    Prometheus Guest

    In article
    <46a580ac$0$31381$>, N
    <> writes
    >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?


    Several assumptions; you use it on a 35mm full frame camera, you make a
    print from the full frame, you view the print at the same distance as
    its diagonal. If you do all three things then the angle between subjects
    in the photograph should be the same as in the original scene. It has
    noting to do with the angle of view of the human eye, which is either
    much less if you only consider the fovea, or much more if you understand
    how human vision works. It also has nothing to do with the ease of
    manufacturing the lens, otherwise sub-miniature (small sensor) and large
    format cameras would all use 50mm lenses. Although the normal for 35mm
    full frame should be 43mm, which makes the 'correct' viewing distance
    for a frame taken with a 50mm lens 1.15 times the diagonal. Why 50 was
    adopted instead of 43 is a question for more research; perhaps marketing
    and being able to describe it as a two inch lens, but this is surmise on
    my part.

    --
    Ian G8ILZ
    There are always two people in every picture: the photographer and the viewer.
    ~Ansel Adams
     
    Prometheus, Jul 24, 2007
    #6
  7. N

    frederick Guest

    Jürgen Exner wrote:
    > N wrote:
    >> "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.

    >> Does your eye have an angle of view of 46 degrees? Mine is certainly
    >> wider than that.

    >
    > Certainly. But you don't really 'see' with your peripheral vision. The area
    > that you _conciously_ see and focus on is approximately equivalent to the
    > 50mm angle of view.
    >

    No it's not.
    The fovea centralis FOV is about 2 degrees, so what you focus on clearly
    is much less than 50mm "equivalent".
    As pointed out further up the thread, that FOV is boring anyway.
    If you look at interesting photos in most galleries, you'll typically
    find that the FOV assumed to have been used in the photos was much
    longer - or much shorter than "normal" focal lengths. Wedding and other
    snapshot artists won't agree, it's subjective, and YMMV.
     
    frederick, Jul 24, 2007
    #7
  8. "frederick" <> wrote:
    >>
    >> Certainly. But you don't really 'see' with your peripheral vision. The
    >> area that you _conciously_ see and focus on is approximately equivalent
    >> to the 50mm angle of view.
    >>

    > No it's not.
    > The fovea centralis FOV is about 2 degrees, so what you focus on clearly
    > is much less than 50mm "equivalent".


    And one's peripheral vision is way wider than 50mm equivalent: it's more
    like 20mm or wider. I'm finding that (with care, lots of care) even 12mm (on
    FF) can feel about right.

    > As pointed out further up the thread, that FOV is boring anyway.
    > If you look at interesting photos in most galleries, you'll typically find
    > that the FOV assumed to have been used in the photos was much longer - or
    > much shorter than "normal" focal lengths. Wedding and other snapshot
    > artists won't agree, it's subjective, and YMMV.


    Still, a lot of great photos have been taken with the 50mm FOV. Here's a
    photo I'm fond of (inexplicably, you'll probably find), although it's taken
    with a 75mm lens (on 6x6 with an early 1950's Rolleiflex).

    http://www.pbase.com/davidjl/image/37431099/large

    David J. Littleboy
    Tokyo, Japan
     
    David J. Littleboy, Jul 24, 2007
    #8
  9. N

    Alex Monro Guest

    Prometheus wrote:

    > In article
    > <46a580ac$0$31381$>, N
    > <> writes
    >>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?

    >
    > Several assumptions; you use it on a 35mm full frame camera, you make
    > a print from the full frame, you view the print at the same distance
    > as its diagonal. If you do all three things then the angle between
    > subjects in the photograph should be the same as in the original
    > scene. It has noting to do with the angle of view of the human eye,
    > which is either much less if you only consider the fovea, or much more
    > if you understand how human vision works. It also has nothing to do
    > with the ease of manufacturing the lens, otherwise sub-miniature
    > (small sensor) and large format cameras would all use 50mm lenses.
    > Although the normal for 35mm full frame should be 43mm, which makes
    > the 'correct' viewing distance for a frame taken with a 50mm lens 1.15
    > times the diagonal. Why 50 was adopted instead of 43 is a question for
    > more research; perhaps marketing and being able to describe it as a
    > two inch lens, but this is surmise on my part.
    >

    50mm is "normal" for 35mm film cameras because when Oskar Barnack was
    designing the original Leica, he had some spare 2" microscope lenses
    lying about, and they seemed to work well enough with the new frame
    format. As you say, the traditional rule of thumb of a normal lens
    being of a focal length equivalent to the diagonal of the frame would
    suggest 43mm as being the best choice, but I've seen anything from 40
    to 60mm being used.

    Personally, I find I use my 28mm more than anything else on 35mm, and
    the 28mm equivalent setting most often on my digital ultrazoom bridge,
    but I do tend to shoot more landscapes than anything else.
     
    Alex Monro, Jul 24, 2007
    #9
  10. Alex Monro wrote:
    []
    > Personally, I find I use my 28mm more than anything else on 35mm, and
    > the 28mm equivalent setting most often on my digital ultrazoom bridge,
    > but I do tend to shoot more landscapes than anything else.


    I found that with my Nikon 5700, I was using the widest angle (35mm IIRC)
    a lot of the time, and therefore I decided to get the 24-85mm Nikon 8400.
    Trouble is that I like telephoto as well.

    There's a handy little program here (free) which will show you what focal
    lengths you are using in a set of images:

    http://www.cpr.demon.nl/prog_plotf.html

    Cheers,
    David
     
    David J Taylor, Jul 24, 2007
    #10
  11. N

    WalkingMan Guest

    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
     
    WalkingMan, Jul 24, 2007
    #11
  12. 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.
     
    Don Stauffer in Minnesota, Jul 24, 2007
    #12
  13. "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/articles.html#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/articles.html#perspective-types,
    which covers among other things FL-format relationships.
    --
    David Ruether

    http://www.donferrario.com/ruether
     
    David Ruether, Jul 24, 2007
    #13
  14. N

    Allen Guest

    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
     
    Allen, Jul 24, 2007
    #14
  15. N

    C J Campbell Guest

    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
     
    C J Campbell, Jul 24, 2007
    #15
  16. N

    Gino Guest

    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
    news:f840dj$b00$...
    >
    > "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.
     
    Gino, Jul 24, 2007
    #16
  17. 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, Jul 24, 2007
    #17
  18. N

    HEMI-Powered Guest

    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
     
    HEMI-Powered, Jul 24, 2007
    #18
  19. N

    N Guest

    "Andrey Tarasevich" <> wrote in message
    news:f85mis$jgl$...
    >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.
     
    N, Jul 25, 2007
    #19
  20. >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.
     
    /\\BratMan/\\, Jul 25, 2007
    #20
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