Sigma 8mm NPP setting

[Hansen]

I don't know how to interpret what I'm getting and would appreciate some insight.

Using D800 with Sigma 8mm Fisheye.

Shooting 3 around, 1 Zenith, 1 Nadir.

I leveled the camera for the first shot

When I align the 3 around there are no stitching errors.

When I add any one or both of the Zenith and Nadir there are stitching errors.

I have tried deleting and re-adding control points, without and without the masking but it makes no difference.

- 3 around no error;  zenith - error;  nadir - error;  zenith and nadir - error

I've spent a lot of time adjusting the alignment for the NPP (am using Nodal Ninja R-1 ring mount) and as far as my eyes can tell, the lens is at the correct position.

I don't know how to interpret what I'm getting and would appreciate some insight.

Here is the link for the pts. file:  http://ge.tt/9R2Wk7A

Thanks

Bob

.

[Ken Warner]

When you tilt up for zenith and down for nadir, is the lens still exactly at the NPP? Some who use that setup don't take a zenith. They tilt up a few degrees to cover the zenith, then just shoot the nadir.

Maybe some of those people will respond.

[John Houghton]

Bob, Your image 4 is in portrait orientation whereas the others are in
landscape. You should have all in the same orientation. Its best to
turn off the auto rotate feature in the camera to avoid such potential
problems with the nadir and zenith.

As Ken points out, it is difficult to take good zenith and nadir shots
whilst maintaining the position of the entrance pupil, so perfect
stitching may well not be possible with this set of images. Hard to
tell without access to the images.

John

[ROBERT HANSEN]

Ken, the nadir is over the axis point - the zenith is about 80mm offset.
I'll try the "tilt up" thanks

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[Ken Warner]

The lens may be "over" the axis but it may not be at the NPP.

But I defer to those who have a similar setup for final comments.

[ROBERT HANSEN]

John
I'll change the orientation of #4 and see what happens. What's interesting
as the Sigma is a circular fisheye, my camera is mounted landscape as I
didn't think it would make any difference.
Re the Nodal Ninja R1 - when tilting back for the Zenith it offsets about
80mm. As Ken suggested, maybe a slight tilt up will do that job or maybe I
can find a way to center.
For the nadir, I drop a plum-bob from the center column and leave a marker
and then move the camera so the marker is center focused.
Access to images - the file sizes run from 15 to 18KB - started to upload
to ge.tt but its going to be slow because of their size. I'll reduce the
size if you think that won't make any difference with your look; however
with things I have to do will not be able to do this until Friday.
Thanks
Bob

[John Houghton]

On Dec 19, 7:26 pm, "ROBERT HANSEN" <rf...@verizon.net> wrote:
> John
> I'll change the orientation of #4 and see what happens.  What's interesting
> as the Sigma is a circular fisheye, my camera is mounted landscape as I
> didn't think it would make any difference.

Bob, When the camera is pointing straight down (or up), gravity is
acting at right angles to the image sensor. There is therefore no up
or down in the horizontal plane being shot. It's a matter of luck
what the orientation the camera chooses to assign to the orientation
tag in the exif data.

If the ground on which the tripod is set is reasonably flat, an offset
of from the ideal NPP point is of little importance for the nadir as
viewpoint correction can be invoked (in PTGui Pro) to get a good
alignment. Likewise, if there's a flat ceiling above, then the same
trick can be played.

Half size jpegs would be quite good enough if you can upload those.
Thanks.

John

[ROBERT HANSEN]

I mis-stated the lens is NOT over the NPP it is about 80mm offset.

[ROBERT HANSEN]

John
Here's the link to the images: http://ge.tt/9R2Wk7A
Have resized all to 4H x5.00w - 200DPY, 2.7mb(?)
I changed to orientation of #4 - the nadir, but it made no difference,
results the same:
3 around stitch no error (that IO can see), add either 3 or 4 or both,
stitch error
Have not as yet tried the viewpoint correction for the Nadir (a learning
curve for me as have not previously seen need to use it); as you can see it
won't work for the Zenith

Bob

-----Original Message-----
From: John Houghton
Sent: Wednesday, December 19, 2012 3:21 PM
To: PTGui Support
Subject: [PTGui] Re: Sigma 8mm NPP setting

[John Houghton]

Bob, It is as I thought. The nadir image can be stitched in ok with
viewpoint correction applied (using only the flat area). There are
issues concerning tripod shadows, which require more careful
management in the shooting, but alignment-wise, all is well. The
zenith is far more difficult to stitch in because of the quite large
parallax problems. With the R1, you need to shift the tripod
horizontally and also adjust the height with the centre column to
maintain the NPP. I think it best to omit the zenith shot in this
case, and possibly do a second stitch with Smartblend to handle any
minor misalignments caused by branches being blown about in a breeze.
Merge the PTGui blended lower half with Smartblend's upper half to get
the best of both blenders.

My project file is at http://ge.tt/3XPQKxT/v/0

John

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