Nodal points G11

Hi all,

Where are the Nodal points of the G11?
I have no means to find out - who does?

Thanks in advance
flowe

After googling "Nodal points", I am still wondering what you need to know....

How close can it focus? Focal length?

Erik_L wrote in post #8892360
After googling "Nodal points", I am still wondering what you need to know....

How close can it focus? Focal length?

IIRC it is the point around which to rotate the camera so as to get the edge overlap correct in pano's

I think it is a function of sensor plane and focal length

forno wrote in post #8892394
IIRC it is the point around which to rotate the camera so as to get the edge overlap correct in pano's
I think it is a function of sensor plane and focal length

forno, thanks for the clarification. Taking it one step further: the focal length is only a "handle" for the nodal point. Defined it is by lens and body design and the movement of individual lenses, shifting the optical center of the system in a way not readily known. The nodal point is given as distance along the optical axis from the tripod socket plane - with reference to the focal length, but as an entirely different number of millimeters. Consequently, the nodal information pertains to a given lens and body and would be different between say a G6 and a G10/G11.

flowe

Wouldn't the nodal point be exactly in the middle of the lens? So if the tripod mount hole is not exactly over the lens, then you have some corrections to be done, as it'll not rotate around the lens nodal point, but around the tripod mount holes nodal point.

I would assume that if the photo were taken from far enough away, this would be negligible.

CyberPet wrote in post #8896462
Wouldn't the nodal point be exactly in the middle of the lens? So if the tripod mount hole is not exactly over the lens, then you have some corrections to be done, as it'll not rotate around the lens nodal point, but around the tripod mount holes nodal point.

CyberPet: "middle of the lens" is ambiguous - the nodal point lies *somewhere along the optical axis* of the lens. Then you have to take into account the height of the optical axis above camera base plane (if camera vertical), as well as the horizontal deviation of the tripod mount hole from the optical axis. Rotating the camera *truly* around the nodal point is what commercial and makeshift pano adapters are about, i.e. compensating for the deviations in all three axes.

Erik_L: Quote: "I would assume that if the photo were taken from far enough away, this would be negligible." - Right, but panos live with the depth of the subject area, and you wouldn't remain satisfied with all those flat panoramas!

flowe

Wow flowe, that totally went above my head. Thanks for the explanation.

I remeber a PDF file floating around a year ago or so, that set out how to find the nodal point.

I think you need to find 2 object in line with each othe, say telephone poles, position the camera at "straight ahead". At this point you should only see 1 telephone pole with the other being hidden behind the first.

Now rotate the camera to the right, if you can still only see one telephone pole you are rotating at the nodal point.

This is from memory, dont hold me to it

forno wrote in post #8899180
I remeber a PDF file floating around a year ago or so, that set out how to find the nodal point.

I think you need to find 2 object in line with each othe, say telephone poles, position the camera at "straight ahead". At this point you should only see 1 telephone pole with the other being hidden behind the first.

Now rotate the camera to the right, if you can still only see one telephone pole you are rotating at the nodal point.

This is from memory, dont hold me to it

Perfect, you need to move the camera on a slider to find the perfect point, but you hit it on the nail head.

Good shooting
Daryle

I have experienced this accidentally while shooting macros with reflective surfaces. It appears that no matter how I rotate the camera, I can see "Canon" reflecting off the glass. If is shift it just slightly and then rotate it, I can get the correct angle to lose the "Canon" from showing up.

Erik_L wrote in post #8911736
I have experienced this accidentally while shooting macros with reflective surfaces. It appears that no matter how I rotate the camera, I can see "Canon" reflecting off the glass. If is shift it just slightly and then rotate it, I can get the correct angle to lose the "Canon" from showing up.

I think a polarizing filter will fix your problem.

I tried to establish G11 nodal points with a rather elaborate setup - tripod, pano head, Soligor slide and two suspended blue and red sewing threads loaded with screws in 80 and 100cm distance. But sorry, no success. Lining up and focussing straight ahead was easy, but after panning to the edges of the monitor, I haven't been able to establish conclusive results. On the wide end, the threads became almost invisible. So for the time being, I gave up. Any better ideas?

On the other hand, I've done some panos - even with handheld camera - lining up on assembly without the slightest ghosting etc. At present, I prefer "PanoramaStudio 2.0" by http://www.tshsoft.de with very pleasing results. It doesn't look like versions other than in German would be available, but a very decent user interface might help without knowing the language - a demo version is available. PanoramaStudio reads all required info from EXIF and applies correct debarrelling automatically. (BTW: what are experiences with the Canon supplied pano software?)

I feel that the nodal question is probably not very critical with the G cameras and similar (due to the narrow optical system?) Sensibly lined up on a pano head plus appropriate software will produce most satisfactory results. One more aspect: camera in vertical position makes for a larger vertical view angle and less panning between shots and therefore a less critical nodal issue.

Good pano!
flowe

Re: Canon pano software - I've had fairly good results with this software and my G9. However, I more often prefer the results achieved using the free Microsoft ICE software for panos.

Dennis

Hi flowe

I think you will do a great job with your setup, except for one thing:

You do not need thin threads to do the job, and it is better to place them near to the lens the first reference, (say, 80cm) but the second one far enough to simulate infinite. I used a 19mm aluminum tube close to the camera, I think it was at 100cm from the lens, and a tall pole (12 meters) holding a lighting fixture in the street, 50 meters from the lens. It worked, with the knowledge and guidance of Terrywoodenpic. Check one of his threads: G3 G5 accurate nodal points.