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percepts
12-09-2009, 06:23 AM
Hello,
I read the instructions on how to locate the entrance pupil but I would like to use an NN3 with a film rangefinder camera. That means the viewfinder is not looking through the lens and will see parallax when camera is rotated.
So my question is: How do I work out where the entrance pupil is on a film rangefinder camera? Is there a special technique for this kind of camera. I will probably be using 35, 50 or 85 mm lenses.

Thanks.

nick fan
12-09-2009, 07:35 AM
you can use a laser pointer to trace the entrance pupil of your lens without the camera.
http://michel.thoby.free.fr/SIGMA8mm/Alpha%20test%20300D/Nodal%20point%20of%20SIGMA%208mm.html



Nick

percepts
12-09-2009, 08:29 AM
Thanks, that looks simple enough...

DemonDuck
12-09-2009, 09:46 PM
That procedure doesn't make any sense to me. I must not be understanding it.

Seems a lot simpler just to take a series of pairs of pictures adjusting the camera 1mm or 2mm forward or backward and see where the parallax is less toward the edges of the image. You don't care about parallax in the middle of the image because you won't be blending across the center of the image -- usually. And the NPP for the edge of the lens is different from the middle which you don't care about. It's the edges of the images that are blended and you need to be concerned about parallax there.

John Houghton
12-10-2009, 02:16 PM
And the NPP for the edge of the lens is different from the middle which you don't care about.
This is not true of the three rectilinear lenses to be used by DemonDuck. It's mainly fisheye lenses that suffer from a variable NPP.

John

Hugh
12-21-2009, 03:46 AM
percepts may also find this page some help:
http://www.hugha.co.uk/NodalPoint/Index.htm