zenith and nadir question

[capedoryus]

Hello folks, I have been using Johns tutorial (Thanks again) on adding
a nadir to an image. It has helped me a lot and the idea of using 2
shots straight down at 45 degrees apart has been great. It leaves a
very small hole to fill. The question I have today is on the zenith.
Would it be wise to use the same technique, 2 straight up 45 degees
apart ? I am having problems with power lines not aligning when adding
a handheld zenith shot. Most of the Zenith is perfect through control
points but the matching of wires, in mid air, are almost always off. I
was using photoshop to distort a zenith image and then patch after
placing the zenith in the center as a circle. I would like to use the
photoshop fill as little as possible. Any help is appreciated on
adding the zenith. Lens is a 8mm sam yang on a D7000. Usual is 5 shots
around @ 0 degrees, 2 down @ 90 degrees (each 45 degrees apart), 2
hand held, zenith and nadir. Thanks in advance. Any feedback is
appreciated.
John Conway
ps thrilled with Nikon D7000 and new found detail in panos

[John Houghton]

On Oct 2, 6:06 pm, capedoryus <capedor...@gmail.com> wrote:
> Hello folks, I have been using Johns tutorial (Thanks again) on adding
> a nadir to an image. It has helped me a lot and the idea of using 2
> shots straight down at 45 degrees apart has been great.

Actually, I recommend 90 or 180 degrees apart.

> I am having problems with power lines not aligning when adding
> a handheld zenith shot.

Why handheld?

> Most of the Zenith is perfect through control
> points but the matching of wires, in mid air, are almost always off.

Wires frequently shift between shots - blown by the wind. Some
editing may well be unavoidable to correct minor glitches in the
alignment of the wires. Shoot the zenith with the camera on the
panohead and align it with control points on fixed features.
Precisely how the zenith is merged in would depend on how much of the
overhead wires is captured. Masks in PTGui might be enough, otherwise
output two stitched equirectangular images: one containing only the
zenith shot and the other containing only the blended remaining
images. Use the usual methods of extracting rectilinear zenith views
for merging carefully in Photoshop.

John

[Erik Krause]

Am 02.10.2012 19:06, schrieb capedoryus:
> The question I have today is on the zenith.

Usually there are little problems with zenith in general. Sincee you can
shoot from tripod and your panoramic haed - if aligned correctly - will
produce no parallax errors you can simply load the zenith image together
with all images and align it. Wires are a problem, though, as John writes.

With your combo you should get a relatively small zenith hole whic can
be filled with one zenith shot. However, if there is plain sky in that
shot it might be better not to tilt 90� upwards, but a bit less in order
to have some horizon at least at one side in order to find control
points. In difficult cases it might be worth to shoot 2 or 4 zenith
images (180� or 90� apart), to have enough material to choose from. Use
masking and detail viewer in that case.

Broken wires can be mended in Photoshop if you extract a zenith view
from the panorama, duplicate the background to a layer, in this layer
select a rectangular area containing the wire and use the Free Transform
tool to stretch and distort the wire until it fits again. Use an area as
long as possible to prevent visual bends in mid air. Once the wire
matches again you can hide the seams painting a soft layer mask.

--
Erik Krause
http://www.erik-krause.de

[co...@vaxxine.com]

Hi everyone

Does anyone know how PTgui decides how a zenith shot is oriented?...the issue is
that sometimes it puts the zenith sideways in the initial image load...so then I
have to quit the program, and rotate it in photoshop etc


Phil

[Erik Krause]

It uses the orientation value from EXIF data. It is advisable to disable
orientation sensor in camera if you shoot for panoramas (such that the
images don't get rotated automatically when displayed on a computer).

[John Houghton]

On Oct 2, 10:04 pm, co...@vaxxine.com wrote:
> ...so then I have to quit the program, and rotate it in photoshop etc

It's not enough to simply rotate the image into portrait or lndscape
to match the others; it's important to rotate the image in the right
direction. This is to ensure that the lens horizontal and vertical
shift parameters apply correction in a consistent fashion. If you use
Photoshop's Bridge, you can display the orientation tag in the
Metadata panel and rotate all images to display the same orientation
value (usually -90 for portrait). You may have to visit Edit-
>Preferences->Metadata to select the orientation tag for inclusion in
the panel display.

But, as Erik suggested, it is simplest to disable the auto rotation
feature in the camera.

John