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View Full Version : in regards to lens filters and the change in nodal point



IgoNodaLBoiNG
05-07-2008, 12:57 AM
im wondering when working out the nodal point is it the point were the light enters the lens front element glass or say if i was using a canon 70-200f4 would the nodal point be the front glass or the glass in side the lens which zooms in and out not that im using said lens as its impossible as its to long but just in relation to the nodal point and were it enters ie is it the front element allways and if im using filters do i need to adjust my setting just wondering im a noob dam hate that word but yeah i also wish to use cokin filter setup and are wondering what the story is with the noodle point there any info would save me some playing around thx in advance Igo

nick fan
05-07-2008, 03:31 AM
NNP would not be changed by adding filters. It will be changed by adding conversion lens.


nick

IgoNodaLBoiNG
05-07-2008, 03:38 AM
hey thx mate the nodal point is were the light enters the front element yeah ?

John Houghton
05-07-2008, 03:42 AM
The no-parallax point (NPP) is really the entrance pupil of the lens rather than the nodal point (which is located somewhere else). The entrance pupil is the virtual image of the aperture formed by the lens elements in front of it. When you look into a lens and see the aperture, the hole at the centre is the entrance pupil, just like your eye. If you hold the camera with its back pointing at a bright light, the light entering the viewfinder eyepiece will be reflected to the lens and you will see the aperture illuminated as a bright disc. You need to stop down the lens to f/22, say, using the depth of field preview button (if there is one) to give a small spot. With your two eyes, you can gauge its position without difficulty. If you operate the zoom, you will see the spot move. At 70mm, the entrance pupil is approximately half way along the lens barrel. At 200mm, it is back near the lens mount. A thin lens filter won't affect the NPP significantly.

John

IgoNodaLBoiNG
05-07-2008, 02:12 PM
hey thx thats makes me alot happier as im thinking i wouldnt be able to use many of my lenses but this changes things dramatically ive been using the front element things have still stitched real nice and when i test the paralax like lining up some vertical points it allways seems pretty close but now ile be able to get it even tighter
wish they gave some marks on the lenses were the aperture is as my eyesight is pretty ordinary at the best of times and using digital dont think the light will shine from back through the veiwfinder though will it ile have to check thx mate for that info much appreciated =]

John Houghton
05-08-2008, 01:14 AM
dont think the light will shine from back through the veiwfinder
I was assuming you are using a conventional DSLR. Light entering the lens is reflected up into the viewfinder by the mirror. The light paths are reversible. Light entering the viewfinder will be reflected down and out through the lens.

John

IgoNodaLBoiNG
05-08-2008, 02:41 PM
yeah im a noob dam hate that word off on a wander and photo getting mission tomorow will check it so ile set my nodal point at the aperture blades and i shall see how she go`s
thx john for the info