Re: Life-size objects in the viewfinder


sfeher@xxxxxxxxx wrote:
Hi All,

As I am trying to educate myself in the physics of the camera, I have a
question regarding the focal length for which you get objects to
*appear* life-size in the viewfinder? Is this important in any way?

Looking through the viewfinder the objects appear to be life-size at
aprox. 70mm ?! This happens for both DSLR (D70 - 18-70 lens) and 35mm
SLR (Elan7 28-90
lens - which has a bigger viewfinder).

I thought the focal length for real life-size would be 43mm for 35mm
camera and somewhat proportional(1.5x) for the DSLR, hence my confusion
when I actually got 70mm for each one of them.

I hope my question is somewhat clear. It could be that I am looking at
the problem from a weird perspective as I am learning these things. If
so please let me know.


This will vary with the camera. Most DSLR viewfinders are essentially
a telescope. The prism re-inverts the image, so the type of telescope
is the same as a 'spotting scope'.

A telescope does have magnification, though not the same mathematically
as the 'magnification' of a simple lens. The telescope 'magnification'
is in angle space. The magnification of the scope depends on the ratio
of the fl of the eyepiece lens to the objective lens. Thus if two
cameras have different eyepiece lens fl, the magnifications will be
different even with the same fl objective lens.
Regards,
Sebastian

.

Relevant Pages

  • Re: Nikon D40 with 300mm lens AND teleconverter (Nikkor AF-S Teleconverter TC-20E II)
    ... Presumably he already knows that magnification is ... For Greg, in using a camera like the D40, I believe he's better off thinking ... while with long lenses one thinks of magnification. ... I've never heard anyone argue that a 100mm lens on a 35mm camera is a good ...
    (rec.photo.digital.slr-systems)
  • Re: Nikon D40 with 300mm lens AND teleconverter (Nikkor AF-S Teleconverter TC-20E II)
    ... Presumably he already knows that magnification is ... For Greg, in using a camera like the D40, I believe he's better off ... thinking of the view through an attached 100mm lens as a 100mm view, ... terms of 35s, has no other reason to think in terms of 35mm equivalencies, ...
    (rec.photo.digital.slr-systems)
  • Re: Nikon D40 with 300mm lens AND teleconverter (Nikkor AF-S Teleconverter TC-20E II)
    ... by 1.5 to get the equivalent filed of view, so the 18-55mm kit lens ... Presumably he already knows that magnification is ... Are you telling me that when you think "18mm on a 1.5 factor camera", ... "a perspective similar to the human eye" since the eye sees in an ...
    (rec.photo.digital.slr-systems)
  • Re: Bob Hatch, camera gear
    ... lens to its maximum zoom setting. ... Unless this is to be a dedicated flying camera, though, the ... I was speaking of shooting with high magnification. ...
    (rec.outdoors.rv-travel)
  • Re: Binocular-Photo camera
    ... Magnification for example has meaning for a visual telescope which may or may not be used with the eye, likelwise for binoculars, microscopes, and hand magnifiers. ... It has meaning for an add on afocal lens which changes the image scale of a camera or for a zoom lens which change the image scale over a range of ratios. ...
    (sci.optics)
Loading