Problem stitching a panorama in PtGUI

[Samotano]

I am trying to stich a panorama that I shot 10 years ago on film and having difficulties with the results. 
Background:
2 horizontal shots
~10% overlap
Shot on slide film (scanned at 4000dpi)
Handheld
Vague recollection of lens (I think 70-200 @ 70mm)
PtGUI 9

Problem:
In some areas the stich does not line up correctly. 
The image is a view of distant fields (2/3), followed by the sea(1/6), followed by the sky (1/6). Some of the control points I had to modify to make them accurate.  The distant fields have enough features for the control points.  However, the sea and the sky are featureless and so no control points.  The sea horizon line is exactly where the stich fails, quite noticebly.

When I run the optimization in PtGUI it says "not so good".
I am looking for ways to improve the stitch.  I am also looking for ways to improve the choice and placement of control points (both manually and/or automatically).  This is becuase the distant fields are quite dark and I have a hard time identifying features, let alone exact placement.  I thought of modifying the shots in photoshop to drammatically increase separation of tones to make the identification and placmement of control points easy and then run the project on the original shots. Perhaps there are easier ways.

[elf]

I'd try Microsoft ICE (or AutoPano Pro) first to see if they can build the pano for you. 10% overlap will make it hard for any program to stitch the pano unless you rotated accurately on the entrance pupil.  If the sky and sea frames are really featureless, you could arrange them in Photoshop, pick x,y co-ordinates that match, then use those co-ordinates as control points in PtGui. I've done that in PTAssembler with some success.

[Samotano]

I'd try Microsoft ICE (or AutoPano Pro) first to see if they can build the pano for you. 10% overlap will make it hard for any program to stitch the pano unless you rotated accurately on the entrance pupil.  If the sky and sea frames are really featureless, you could arrange them in Photoshop, pick x,y co-ordinates that match, then use those co-ordinates as control points in PtGui. I've done that in PTAssembler with some success.

Thanks for the suggestion.  I just tried using MS ICE and it gives the same problem.  Also there are no options whatsoever to help with the control points.

[BernardLanguillier]

Hey,

With PTgui, you can delete control points from the list. I would delete all those with an error higher than 2 and try doing another round of optimization.

Then you can also output your pano in multi-layer mode, which will enable you to tune some possibly remaining issues by masked in photoshop.

But overall, I would indeed give CS5 and autopano pro a try.

Keep in mind that with film, you add possible scanning alignement and film flatness issues on top of the original capture issues. It makes it hard for advanced pano software because they tend to assume things. PS CS5 is a more generic blending engine and might do a better job this time around.

Cheers,
Bernard

[elf]

Yes, ICE is an all or nothing stitcher.  It can sometimes stitch images that are difficult in other stitchers. 

If Bernard's suggestions don't work for you, then the last thing to try is just aligning all of the images manually in Photoshop and using free transforms to fit everything together.