How to manually level pano? (It used to work, but now it doesn't)

[Harry Shin]

Hi, 

I do have the current version of PT Gui.   In the past, when I needed to slightly manually level a pano, I simply clicked on part of the pano, and slightly dragged it up or down (I think I also pressed the control key (mac).     Now, no matter what mouse / keyboard combo, I can't seem to be able to manually straighten out a pano (ie to be able to bend the image).    I can rotate the pano, I can move the entire pano up / down but I cannot bend / warp it.   

Q?  What is going on? and more importantly, what's the solution.   

Thanks in advance,  Harry

[John Houghton]

Probably the explanation for your difficulty is that the angle of view of your panorama image is not very big.  Levelling is achieved simply by shifting/rotating the image on the spherical stitching surface.  There is no actual bending of the image.  It retains its shape no matter where it happens to find itself.   If you set the output area in the Panorama Editor window to the full 360x180 view, you will see what is happening.

John

[PTGui Support]

Could you check the focal length reported in the Lens Settings tab after
optimization? Does it still match the actual focal length of the lens?

It's possible that PTGui has optimized the focal length to a value
that's not the actual focal length, resulting in lower control point
errors. This is almost always the result of parallax, so check your
shooting method. It will only happen for partial panoramas; with a full
360 degree panorama PTGui will always have a clue about the correct
focal length (otherwise the ends wouldn't meet).

To fix it you can try this: in the Lens Settings tab set the focal
length to the proper value. Then go to the optimizer tab and uncheck
'optimize lens focal length'. Finally run the optimizer again.

The alignment might be worse, but levelling the panorama will work. If
parallax is severe you might still get uncorrectable curving of the horizon.

Always use a proprly calibrated panoramic head. Or if you shoot
handheld, take care to rotate the camera around the front of the lens,
don't rotate the camera around your body.

If you need more help, feel free to make your images available for download.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

> --
> You received this message because you are subscribed to the Google
> Groups "PTGui Support" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to ptgui+un...@googlegroups.com
> <mailto:ptgui+un...@googlegroups.com>.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/ptgui/0345a7d1-796d-4aa5-99fd-c939a407f30en%40googlegroups.com
> <https://groups.google.com/d/msgid/ptgui/0345a7d1-796d-4aa5-99fd-c939a407f30en%40googlegroups.com?utm_medium=email&utm_source=footer>.

[Harry Shin]

Thanks for the quick responses and thoughts: 

1.  The reason the horizon was messed up in this instance was because I was shooting handheld;  rapid burst while on a boat (the boat wasn't moving, but it was bobbing up / down a bit). 

2.  re: focal length: the data in PT Gui corresponds to reality from my brief review of the data;  I'll look into it in more detail tonight.  

3.  Attached is the image; untouched; obviously the horizon is not level.      I don't understand why but in the past (ie just several months ago), when using PT Gui, in such circumstances, I can move the mouse  (hold it) up  / down and the pano while in the editor would "warp" if that's the correct term.      The old instructions in PTGui  (https://ptgui.com/man/straighten.html) is what I was able to do;  problem is that this no longer works and I don't have the faintest idea why.    Basically, I would love to do what PT Gui recommend (as via the old instructions);   what's going on with these newer versions??? 

Thanks in advance,  Harry

[John Houghton]

Harry, PTGui still works exactly the same as it ever did.  Here's an example:

To do anything sane with your stitched image, it is necessary to know the angular width and projection of the image, and also take account of the effect cropping has on the position of the horizon (normally across the centre line) by adjusting the lens vertical shift parameter.  That enables the position and size of the image to be replicated correctly in the project.  Adjustment of the composite image in the original project will work exactly the same.  It would be helpful if a copy of the project that generated your image could be supplied.

John

[PTGui Support]

Hi Harry,

As John says, PTGui hasn't changed its behavior. The problem must be
caused by parallax, which must be quite severe if you're shooting from a
boat. Even a few cm up/down will cause parallax problems.

Looking at the image, it might be that PTGui has optimized the Lens
Shift values to some unrealistic value. You might try this:

- In Lens Settings, once again make sure the focal length corresponds to
your lens focal length
- In Lens Settings, click Reset to reset the lens correction values
- In the Optimizer tab, uncheck 'optimize focal length'
- In the Optimizer tab, set Minimize Lens Distortion to 'Heavy'
- Remove any control points close to the camera (on the water surface)
and check you have sufficient control points in the remainder of the image.
- Run the optimizer

After doing this, levelling must work as expected. Still, you shouldn't
expect a straight line where the water surface meets the gletscher,
because that's not the horizon. The horizon would be somewhat above
there (but you can't see it).

In most projections, only the horizon will be a straight horizontal
line, other horizontal lines will be curved. The exceptions are the
transverse projections and rectilinear projections, but those will have
different trade offs. Try and see if they work for this image.

Feel free to make your project available for download if you would like
me to try.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

> www.ptgui.com <http://www.ptgui.com>

> <https://groups.google.com/d/msgid/ptgui/0345a7d1-796d-4aa5-99fd-c939a407f30en%40googlegroups.com?utm_medium=email&utm_source=footer
> <https://groups.google.com/d/msgid/ptgui/0345a7d1-796d-4aa5-99fd-c939a407f30en%40googlegroups.com?utm_medium=email&utm_source=footer>>.

>
>
> --
> You received this message because you are subscribed to the Google
> Groups "PTGui Support" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to ptgui+un...@googlegroups.com
> <mailto:ptgui+un...@googlegroups.com>.
> To view this discussion on the web visit

> https://groups.google.com/d/msgid/ptgui/4c5c5230-7f06-4173-903f-97e68af19db7n%40googlegroups.com
> <https://groups.google.com/d/msgid/ptgui/4c5c5230-7f06-4173-903f-97e68af19db7n%40googlegroups.com?utm_medium=email&utm_source=footer>.

[John Houghton]

Harry, One way to tackle this stitch is to first align the images using control points only on the distant rocks and glacier, for which parallax will hopefully not be a major problem..  Ignore any alignment problems in the flat surface of ice/water.  Then add the images a second time and align the added images using control points only on the flat sheet of ice/water, except also include points on the distant shore line between both sets of images to anchor them in place.  Set viewpoint correction on the second set of images.  Apply masks to select the glacier etc from the first set and the water surface from the second set.  I have used this technique several times for difficult hand-held panoramas with parallax problems and it can work very well.

John