PDA

View Full Version : Re-level or not?



Johnytuono
09-02-2013, 02:23 PM
Hi
Should I re-level the tripod for the Nadir patch shot or not......I seem to find conflicting views.
Also I find in PTGui that Viewpoint correction works better if I tick both the Nadir shots. Does that seem right? In fact, I actually loaded all the images (including Nadir2), ticked VP for the 2 Nadirs and it stitched perfect, then masked and the Nadir looked perfect...........couldn't remember if I re-levelled though between Nadirs, hence the question.
Thanks
John

BTW is there a reason for masking everything but the floor for Nadir2?

nick fan
09-02-2013, 07:11 PM
you should not re-level the images taken at NPP. Re-leveling move lens away from NPP.
You can re-level the nadir shots. With the weight of camera and lens further away from tripod center, the lens axis will be tilted towards center column, even with the strongest tripod.

Nick

John Houghton
09-03-2013, 12:43 AM
Should I re-level the tripod for the Nadir patch shot or not......I seem to find conflicting views.
When you are making use of viewpoint correction, it's not necessary to re-level the tripod. It's a complete waste of time. Re-levelling is only needed in order to preserve perspectives when merging nadir images before stitching (e.g. when using a stitcher not having viewpoint correction facilities).


Also I find in PTGui that Viewpoint correction works better if I tick both the Nadir shots. Does that seem right?
In theory, a nadir shot taken at the NPP by simply rotating the camera downwards on the panohead should not need viewpoint correction. In practice, the NPP is rarely perfectly maintained as the head is moved into the nadir position, so invoking viewpoint correction may well offer a useful fine tuning of the alignment, particularly if the head is poorly set up.


BTW is there a reason for masking everything but the floor for Nadir2?
Viewpoint correction only works for features lying within a plane surface (level or sloping). Any parts of the scene located outside of the flat plane will not be corrected to bring them into alignment with the corresponding parts of overlapping images. So items poking up or down from the plane need to be masked out. It's ok to have a 3D object in the central area of the nadir, but take care to keep control points off it and if necessary apply masks to ensure that only one complete view of it makes it through to the blended panorama.

John

nick fan
09-03-2013, 10:01 AM
Hi John H,

I assume Johnytuono refer nadir shots to those taken with nadir adapter at swung out position.

NIck

Johnytuono
09-03-2013, 10:15 AM
Hi
Yes I meant with the Nadir adapter swung out and not re-levelling for the 'normal' Nadir shot or any other shots in the 360 rotation.
Anyway I tried both ways....re-levelling for Nadir2 and without re-levelling for Nadir2...and with these shots I tried the various configurations of VP for Nadir and Nadir2.....end result was perfect for both Nadir2 shots (re-levelled and not) but with VP ticked for both Nadir and Nadir2........but ooops.....forgot to take the Zenith lol.

hindenhaag
09-03-2013, 11:00 AM
John,

You only level your first shot. Then go around and do all your shots. After importing to PTGui, you have to fink the "viewpoint correction" in >Optimizer > Advanced only for the Nadir2 shot because it is the only shot not done in NPP.
BTW,in >optimizer I always use "minimize lens distortion" with "heavy + lens shift".

Have a look at this: http://ge.tt/7JVt50e/v/1

https://vimeo.com/65994333

Your spacer is on it's way and should arrive within around 3 workdays.
Heinz

Johnytuono
09-03-2013, 01:42 PM
Thank you for that Heinz.......look forward to receiving it.
John