PTGui 9.1.3 Fails to Level Horizon

[Alan MW]

I have PTGui 9.1.3. When I try to combine several pictures, I always get a smiling panorama (one that sags in the middle). All efforts by me to correct this have, so far, been in vain. I have tried putting horizontal control points on the image and doing "Level Panorama" on the Edit menu - no correction happens, and no error message happens.

Before I move on to some other product (hopefully less expensive), has anybody any advice that would resolve this?

Cheers, Alan W

[PTGui Support]

Hi Alan,

What if you drag the panorama upwards in the Panorama Editor (also increase the vertical field of view using the slider). If that doesn't help, could you make your project available? Just the .pts file would suffice.

Kind regards,

 

New House Internet Services BV

Joost Nieuwenhuijse

 

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[Alan MW]

The four images are to be found at http://www.flickr.com/photos/45003267@N06/, and are called IMG_4555 to IMG 4558.

[Alan MW]

I have tried "drag the panorama upwards in the Panorama Editor" without success.

[John Houghton]

Alan, Much depends on where you position the horizontal line control
points and the output projection. The line features upon which the
points are assigned should be expected to be flat and horizontal in
the output image. In cylindrical and equirectangular projections,
usually only the horizon itself should be rendered flat and level.
Vertical line control points are much more frequently employed, since
all vertical line features should be vertical when the panorama is
levelled. See:

http://www.johnhpanos.com/levtut.htm.

You can also level the panorama using the Panorama Editor window.
See:

http://www.ptgui.com/man/straighten.html

John

[DennisS]

Vertical control points are my friend.  I use them for every panorama.  Works 100% of the time.  Nice level panoramas.  I don't level in the Panorama Editor window nor do I ever use horizontal control points.  I start by placing vertical control points on the odd numbered images.  If I need more I put them in the even numbered images.  Works great and the panorama stays level, no matter what else I do to the panorama.

[John Houghton]

On Nov 1, 9:30 pm, Alan MW <a.j.wh...@blueyonder.co.uk> wrote:
> The four images are to be found athttp://www.flickr.com/photos/45003267@N06/, and are
> called IMG_4555 to IMG_4558.

Alan, The images have had the exif data stripped away so there's no
information about the zoom setting used for these images. I used
48mm. I found that the Straighten Panorama option on the Panorama
Editor->Edit menu gave a good level result. However, to illustrate the
use of the horizontal line control points, I assigned two such points
on the line running along under the distant edge under the trees: one
point between images 0 and 3 and another point between images 0 and
1. I have put my project file here:

http://www.ge.tt/2s1TqkQ/v/0?c

Unzip the project file and copy it into the same folder as the
images. Open the file with PTGui and enter Advanced mode by clicking
the button to the right of the Project Assistant. Go to the Optimizer
tab and select Advanced mode there too, where you can see the settings
and run the optimizer.

John

[PTGui Support]

Hi Alan,

Do you remember at which focal length the images were taken? The exif
data is missing, perhaps this was stripped by Flickr.

When straightening such a single row panorama fails, this is often due
to parallax. The parallax causes the optimizer to misestimate the focal
length of the lens. Normally, if PTGui has the correct focal length, a
panorama will be straight as soon as you drag it up or down in the
panorama editor until the horizon matches the center horizontal line.
But if PTGui has estimated a too large focal length, dragging the
panorama upwards or downwards will only move the panorama up or down
without changing the curvature. This is what seems to be happening for
your images.

If you know the actual focal length, you can enter it in PTGui and
disable optimization of the field of view (focal length), so that it
keeps using the right value:
- in the Project Assistant enter the focal length of your lens and the
focal length multiplier of your camera
- switch to Advanced mode
- go to the Optimizer tab and uncheck 'Optimize lens field of view'
- run the Optimizer

But it would be much better to prevent this problem altogether. Next
time when you shoot a panorama hand held, keep the front of the lens at
exactly the same position when you take the images. In other words, do
not rotate the camera around your body when taking the images, but
rotate your body around the front of the lens. It's explained in the
video tutorial:
http://www.ptgui.com/videotutorials.html

This prevents parallax problems and PTGui will correctly stitch your
panorama. If it's not level, simply drag it up or down in the panorama
editor (see the second video tutorial).

You can use horizontal line control points for leveling, but keep in
mind that you may only place them on the horizon itself. You cannot
place horizontal control points on other horizontal features above or
below the horizon.

Hope this helps!

Joost

On 1-11-2012 22:33, Alan MW wrote:
> I have tried "drag the panorama upwards in the Panorama Editor" without
> success.
>

[Alan MW]

This is baffling me. I've tried some or all of the things you guys have suggested, and time after time I get a sagging horizon (actually a treeline/field boundary). I want to upload the image files and my project, but they exceed 7 megabytes. How do we proceed?
Alan W

[Joost Nieuwenhuijse - PTGui Support]

Hi Alan,

You can upload your files at a file sharing site (for example http://ge.tt/ ) and include a link in your message.

Joost

On Nov 2, 2012, at 5:14 PM, Alan MW <a.j....@blueyonder.co.uk> wrote:

> This is baffling me. I've tried some or all of the things you guys have suggested, and time after time I get a sagging horizon (actually a treeline/field boundary). I want to upload the image files and my project, but they exceed 7 megabytes. How do we proceed?
> Alan W
>

[AlanWB]

Apologies for the delay. The files are zipped as Temp.zip in http://ge.tt/3eek6nQ/v/0. There's a project file and four images depicting a field and woodland.

I want to make the boundary between field and woodland straight. It always sags for me :-(

Alan

[Erik Krause]

Am 04.11.2012 21:09, schrieb AlanWB:
> Apologies for the delay. The files are zipped as Temp.zip in
> http://ge.tt/3eek6nQ/v/0. There's a project file and four images
> depicting a field and woodland.
>
> I want to make the boundary between field and woodland straight. It
> always sags for me :-(

You have severe parallax in your images, this means you didn't rotate
the camera around the no-parallax point. This is essential for a good
stitch.

However, I managed to get the boundary between field and woodland
straight. First you need to delete all controlpoints on the field:
shift-drag an area on Control Points tab and press delete key.
Then on Project Assistent tab uncheck and check again "Automatic (use
EXIF...) in order to rest the focal length to the EXIF value.

Then press F5 to optimize. After that in Panorama Editor press Fit
Panorama and Center Panorama. Then you should be able to drag the
panorama upwards (boundary to center line) with the left mouse button,
then drag-rotate it with the right button to be level. Press Fit
Panorama again to get it fill the canvas and drag the edge of the canvas
in order to crop it.

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

[AlanWB]

Erik,

Thanks for the advice about parallax.

I tried to repeat your procedure, but I still got a saggy panorama. I can't spend any more time on this tonight, but I might have another go some other time.

Thanks.

Alan

[Erik Krause]

Am 04.11.2012 22:14, schrieb AlanWB:
> I tried to repeat your procedure, but I still got a saggy panorama.

Perhaps you forgot the control points between images 0 and 2...

Find your project file here: http://ge.tt/1tZuDwQ/v/0

[Matthew Ward]

Your picture appears to be fairly curved in reality.

Select the Panorama editor > CMD e

Select Equirectangular (the sphere)

Select the edit entire panorama button

Drag the right slider to about 40 degrees to make your canvas bigger

drag the image upwards until the horizon appears straight.

You will need an image editor to crop the excess canvas when you output the image.

Best

Matthew Ward

[John Houghton]

On Nov 4, 9:14 pm, AlanWB <a.j.wh...@blueyonder.co.uk> wrote:
> Erik,
>
> Thanks for the advice about parallax.
>
> I tried to repeat your procedure, but I still got a saggy panorama.

Mostly doing the same as Erik, I levelled the panorama with horizontal
line control points. I also deleted image 1, which is more-or-less
identical to image 0. I have uploaded my project file and stitched
image at:

http://www.ge.tt/5YbEbxQ/v/0?c

Panorama blending is compromised by variations in exposure and white
balance, and also by the effects of parallax. Auto exposure and white
balance camera settings should be avoided, and as already mentioned, a
panorama head is also recommended. I output a PSD layered file and
after some manual image adjustements used the auto blend option in
Photoshop for the result included in my upload.

John

[AlanWB]

John,

Many thanks to you, Erik, Mathew, et al. Success!

I have tried the various techniques you suggested and I am now confident that I can fix saggy horizons in future. (And avoid the pitfalls in the field that make it difficult.)

Alan W