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View Full Version : Doubler moves or not nodal point ?



Vincèn
03-04-2011, 09:49 AM
Hey,

Unhappy I have not time right now to test myself but something comes in my mind. Does use of doubler on a camera moves the nodal point ? I bet not as nodal point is depending of lens ! So if I use a doubler I should just offset my camera on upper rail of length size of doubler !
Is it right ? someone has some experiences to share ?

Thanks,

Vincèn

nick fan
03-04-2011, 06:51 PM
Hey,

Unhappy I have not time right now to test myself but something comes in my mind. Does use of doubler on a camera moves the nodal point ? I bet not as nodal point is depending of lens ! So if I use a doubler I should just offset my camera on upper rail of length size of doubler !
Is it right ? someone has some experiences to share ?

Thanks,

Vincèn

what is a doubler? dual image? or 2x extender?

Nick

hindenhaag
03-04-2011, 10:50 PM
Nick,

I suppose Vincen talks of a 2x converter

Heinz

Vincèn
03-04-2011, 11:43 PM
what is a doubler? dual image? or 2x extender?
oups sorry for confusion :blush: I'm thinking about 2x Converter :) (the equipment you install between body and lens that double focal length of your lens !

Vincèn

hindenhaag
03-04-2011, 11:54 PM
Vincen,

on 70-200? I think we have to try it on the lens. I googled, but did not find info for Nikon converters and the consequences for NPP once being connected. So we have to test it.

Cheers,
Heinz

Vincèn
03-05-2011, 12:07 AM
on 70-200? I think we have to try it on the lens. I googled, but did not find info for Nikon converters and the consequences for NPP once being connected. So we have to test it.
For now I wanted to test it on 14-24 but it's not Nikkor one extender I have (it's Kenko/Tamron one I have). I used it successfully already with 70-200 to build gigapixels panorama (http://www.skivr.com/?p=899). I'm pretty sure it doesn't change NPP as it's something inside the lens, and converter just move awat lens from body ! I'll do a test today quickly to check if it changes something or not ;)

Vincèn

John Houghton
03-05-2011, 12:08 AM
The NPP is, as we know, the position of the entrance pupil rather than the nodal point. The entrance pupil is the virtual image of the aperture formed by the lens elements in front of it. Inserting a 2x converter between the lens and the camera body can therefore have no effect on the position of the entrance pupil, other than shifting it forwards by the thickness of the converter. If using the converter necessitates a significant change in focus setting, then that might conceivably affect the NPP.

John

Vincèn
03-05-2011, 03:31 AM
Hum it looks like I'll need to do the test with M1 as NN5 is too short on upper rail to install both 14-24 lens, doubler, and body (whatever I use D3 or D90 !). So let's test that probably next week when I'll get my M1 :)

Vincèn

Hugh
03-09-2011, 06:53 AM
Vincèn I agree with John and your original comment in that the point we are talking about is the Entrance Pupil of the lens and governed by the elements effecting the incoming light so a "doubler" or "tele-converter" should not change this point.

Although this device effectively changes the focal length of the lens (doubles it) as far as the camera is concerned, this is changing the Exit Pupil of the lens so should have no effect on the location of the Entrance Pupil.

A good place to start, as you say, is to move the camera back by the the thickness of the "doubler" and everything should be fine.

Unfortunately I do not have such a device to test, but I am confident we are right.

Let us know how you get on.
Hugh.