RE: Tolerance

[Dan Irvin <DIrvin@xxxxxxxxxxxxxxxxx>]

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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From: 	Edward Meyers[SMTP:aghalide@xxxxxxxxx]
Sent: 	Thursday, April 29, 1999 4:57 AM
To: 	panorama-l@xxxxxxxxxxxxxxxxx
Subject: 	Re: Tolerance



On Thu, 29 Apr 1999, Robert Durn wrote:

> I have just taken some test shots with my new home made "Roboscope 2"
> camera! It uses 120 film stock and a 24mm Nikon lens. The image measures
> 152mm on the negative for a full 360 degree. Using the 2 x focal length x Pi
> rule it should be 150.796mm. Is this within tolerance? The images are
> sharp-ish but I'm not sure if the lens is mounted at the correct distance to
> the film. Should it be 46.5mm for Infinity?. Any thoughts?
> 
> Rob Durn.
> 
> Also at Robert.Durn@xxxxxxxxxxxxxxxxxxx   
> 
No problem. Marked focal lengths are rarely true. Manufacturers
like to round off the numbers and fudge on the side that's more
desireable. This is why Erickson of Florida, USA, uses zoom
lenses. After the camera is complete he makes tests at slight
focal length variations to find the right one for the "disc".
Ed

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