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Mailinglist:PanoTools
Sender:manfredgruber
Date/Time:2004-Nov-09 10:24:21
Subject:Re: entrance pupil - nodal point

Thread:


PanoTools: Re: entrance pupil - nodal point manfredgruber 2004-Nov-09 10:24:21

Thx for the attached description. 
For me, it`s not clear at all. But if all the measurement for "nodal
point" and "entrance pupil" to avoid parallax error means the same at
the end, it is ok for me.
Is there a picture that could describe it for a visual thinking like
me?

I tried to translate it to german is it correct?
 entrance pupil -> Eintrittsblende
 nodal point    -> Kontenpunkt, optisches Zentrum einer Linse


Regards
   Manfred


--- In #removed#, "sdubose99" <#removed#> wrote:
> 
> Manfred, guten tag... for all intents and purposes of producing a 
> panorama images with little parallax, nodal point and entrance
pupil 
> are the same.  
> 
> Scott
> 
> The following is from John Houghton in the UK:
> 
> Nodal point: When you have a lens made up of two or more elements, 
> the resulting combination of lenses will have an effective focal 
> length "f". On either side of the lens will be the two focal planes 
> where objects located at infinity will be focused. If you measure a 
> distance f back towards the lens from the focal planes, you will 
> arrive at the principal planes. In a simple lens, these will 
> conicide, but in a complex lens they will be separated. The points 
> where these principal planes cross the lens axis are called the 
> principal points. These points are also where the nodal points are 
> located. A light ray incident towards the front nodal point will 
> emerge as from the rear nodal point in a direction parallel to the 
> incident ray. In a camera, if the lens is rotated about the rear 
> nodal point, the image will remain stationary on the film located
at 
> the focal plane. This is an important factor in the design of 
> panoramic cameras in which the lens rotates rather than the camera. 
> 
> Entrance pupil: Somewhere between the elements of a complex lens 
> will be the iris. If you look through the front of a lens, you will 
> see a virtual image of the iris formed by the front elements and 
> this is called the entrance pupil. Likewise, there is an image of 
> the iris formed by the rear elements of the lens called the exit 
> pupil. All light rays passing through the lens pass through the 
> entrance and exit pupils. The front entrance pupil is therefore the 
> centre of perspective of the lens. Rotating the camera about this 
> point will avoid parallax errors. 
> 
> In the context of stitching multiple image panoramas, all the 
> practical methods described for determining the position of the 
> nodal point in fact find the position of the entrance pupil, not
the 
> nodal point. Since it is the entrance pupil that is required, then 
> the methods give the desired result. 
> 
> --- In #removed#, "manfredgruber" 
> <#removed#> wrote:
> > 
> > 
> > Hi,
> > 
> > Can someone explain in easy words what`s the difference between  
> >    lens entrance pupil (centre of perspective)
> > and 
> >    nodal point
> > ? Or is there a good reference somewhere in the internet (i didn`t
> > find)
> > 
> > 
> > Regards
> >    Manfred





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