Velocity Reviews - Computer Hardware Reviews

Velocity Reviews > Newsgroups > Computing > Digital Photography > Life-size objects in the viewfinder

Reply
Thread Tools

Life-size objects in the viewfinder

 
 
sfeher@gmail.com
Guest
Posts: n/a
 
      07-16-2006
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.

Regards,
Sebastian

 
Reply With Quote
 
 
 
 
k-man
Guest
Posts: n/a
 
      07-17-2006
You might be confusing focal length and magnification. Magnification
is where you get "lifesize" images. This is particularly important
with macros, where often you would want a magnification of 1:1. This
is not a very detailed explanation, I know. But there are a lot of
sites out there that have all the details.

Kevin



http://www.velocityreviews.com/forums/(E-Mail Removed) 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.
>
> Regards,
> Sebastian


 
Reply With Quote
 
 
 
 
stauffer@usfamily.net
Guest
Posts: n/a
 
      07-17-2006

(E-Mail Removed) 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


 
Reply With Quote
 
Ed Ruf (REPLY to E-MAIL IN SIG!)
Guest
Posts: n/a
 
      07-17-2006
On 16 Jul 2006 11:13:31 -0700, in rec.photo.digital (E-Mail Removed) wrote:

>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.


You are forgetting to also take into account the magnification of the
viewfinder. For the D70, copied from the fine manual:

Magnification Approximately 0.75 (50-mm lens at infi nity; 1.0 m1)
--
Ed Ruf ((E-Mail Removed))
http://edwardgruf.com/Digital_Photog...ral/index.html
 
Reply With Quote
 
 
 
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
class objects, method objects, function objects 7stud Python 11 03-20-2007 06:05 PM
Viewfinder troubles Powershot A70 Neil Digital Photography 3 09-19-2003 06:43 PM
Olympus D-500L Viewfinder Problem Greg Lovern Digital Photography 0 09-14-2003 07:29 AM
using viewfinder (vs. LCD) on DSLR (Canon 300D hopefully!) Digital Puer Digital Photography 4 09-07-2003 02:47 PM
Dimage Xt viewfinder accuracy? Matthew Halfant Digital Photography 2 08-19-2003 07:52 PM



Advertisments