Stitching art - breaks in continuity

[Jared Bartlett]

Hey all - I've been photographing my wife's artwork in multiple pieces so I can get high-res prints made. Yields about 20 frames. I spent a lot of time getting the setup to be as perfect as possible and in most cases I get really clean stitches. Sometimes though they come out wonky and critical areas don't line up. I add control points to the areas where it is wonky to give more reference and it does literally nothing. plus running optimizations just undoes everything I do. I ran this program a long time ago and more control points always seemed to fix things. What's going on?

[Jared Bartlett]

I should also point out that the camera is in a fixed position and the art is hung on a perpendicular plane to the camera, dead level and plumb. the art is then mechanically moved on that plane on a pair of rails CNC style.

[Erik Krause]

Am 18.12.2020 um 20:41 schrieb Jared Bartlett:

> I should also point out that the camera is in a fixed position and the art
> is hung on a perpendicular plane to the camera, dead level and plumb. the
> art is then mechanically moved on that plane on a pair of rails CNC style.

It would have been better to shoot from a fixed viewpoint in a distance
with a long lens.

However, you might find some hints on
https://www.ptgui.com/support.html#6_5

Is the artwork completely flat? or do some details protrude (even minimal)?

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

[Jared Bartlett]

I'm using a 100mm macro lens. the camera is in a fixed position - doesn't move or pan. The art is layered between 1/4' clear acrylic. There is no parallax as the camera doesn't pivot or move. The art moves on the same plane so each frame is captured in exactly the same light, position, plane - really isn't much reason this software shouldn't be able to work it out. I've seen it do great things but sometimes it just doesn't want to behave. Control points seem to have no control when I add additional ones.

[John Houghton]

On Tue, Dec 22, 2020 at 5:47 PM Jared Bartlett <jbartlet...@gmail.com> wrote:

There is no parallax as the camera doesn't pivot or move. The art moves on the same plane so each frame is captured in exactly the same light, position, plane

The camera is shifting relative to the artwork.  That results in serious parallax issues. 

Did you try the stitching technique described at the link Erik referred you to?

John

[PTGui Support]

Hi Jared,

If you've stitched other mosaics successfully, I would suspect it's
caused by misplaced control points. Perhaps on repeating structures.
Check the control points table for control points with large errors.

Be sure to enter a long focal length (say 2000mm), or use viewpoint
correction. See 6.5.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

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