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RE: measuring the focal length of a lens

  • From: Dan Irvin <DIrvin@xxxxxxxxxxxxxxxxx>
  • Subject: RE: measuring the focal length of a lens
  • Date: Thu, 29 Apr 1999 14:09:50 -0700
I use a nodal slide mounted on an optical bench, with a collimator on one end.  I mount the lens and rock the lens back and forth, once the lens is over the rear nodal point the image no longer moves when the lens is rocked.  

Dan

----------
From: 	Jook Leung[SMTP:jook@xxxxxxxx]
Sent: 	Thursday, April 29, 1999 11:47 AM
To: 	panorama-l@xxxxxxxxxxxxxxxxx
Subject: 	measuring the focal length of a lens

That is good to know that Nikon markings are reliable.

How do you measure the focal length of a lens?
Is there any way for the layperson to do it without an optical bench?

Thanks,
Jook

>46.5mm is the correct flange focal distance for Nikon Lenses.  Make sure
>that in your mounting that the lens mount is parallel to the focal plane.
>We use tolerances of +.0000" -.0005" for our systems, and require
>parallelism to be within .0002".
>
>I have measured focal length on a great many Nikon Lenses and find that
>the focal length marked is usually pretty accurate.
>
>Dan Irvin
>Century Optics.
>dirvin@xxxxxxxxxxxxxxxxx
>
>----------


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Jook Leung    jook@xxxxxxxxx    http://360vr.com    201.894.5881
     360VR Photography - Immersive Imaging - Virtual Tours

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