Photographing flat art

[Spike Mafford]

I am having trouble stitching the multiple files together accurately.

The are and camera are in plane and I am making 24 exposures of each work.   Every time I add control points, the stitch comes out inaccurate.  Blurred, skewed, not lining up.  What am I missing?  I've used PTGUI for this previously and it worked.  I just updated to the current version and am at a loss.

Any suggestions?  I use a mirror and the zig-align system to make sure the work and camera are square.  The work moves across the plane of the camera, which is on a tripod.

The tripod center column is geared and moves up or down but, remains in plane when the tripod is leveled.

Thank you.

Spike

[Erik Krause]

Am 16.08.2022 um 18:48 schrieb Spike Mafford:
> I am having trouble stitching the multiple files together accurately.
> The are and camera are in plane and I am making 24 exposures of each
> work. Every time I add control points, the stitch comes out inaccurate.
> Blurred, skewed, not lining up. What am I missing? I've used PTGUI for
> this previously and it worked. I just updated to the current version and
> am at a loss.

PTGui is primarily intended for stitching together images taken from a
common viewpoint (which eliminates any parallax). Therefore, using a
panoramic tripod head and shooting from a distance with a telephoto lens
is by far the easier way to photograph art.

One way PTGui can stitch these types of images is described at
https://ptgui.com/support.html#6_5.

In theory it should also be possible to use viewpoint correction
instead, but this might cause other difficulties.

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

[John Houghton]

Spike, If you can supply a sample set of images (half size jpegs would be fine), I would be happy to happy to investigate if you haven't yet managed to get an acceptable stitch. 

John 

[Spike Mafford]

Thank you for the response Mr. Krause,

I've attempted using a telephoto lens and a Nodal Ninja panographic head but, it is not effective.

The angle to the work is too great and puts the plane out of focus, even at f18.  If I used a 1200mm lens, it might work but,

the click stops on the pano head are not small enough to accommodate this.

I did implement the adjustments suggested in #6_5 without success.

Spike

[Spike Mafford]

Hello John,

Here is a sample set of images I used for a composite file.  There are 24 images in the series in an effort to create a 20,000  x 20,000 pixel file of the original art.  The original files are 5434 x 7229 pixels, created on an H5D-40 Hasselblad.

Thanks,

Spike

[Spike Mafford]

Hello John,

Here is a sample set of images I used for a composite file.  There are 24 images in the series in an effort to create a 20,000  x 20,000 pixel file of the original art.  The original files are 5434 x 7229 pixels, created on an H5D-40 Hasselblad.

I am including screen shots of my process and the project file.  Images will be in another message.

Any insight is greatly appreciated.  I had to turn over this project to a scanning facility that has a 4x5 scan back.

I guess that’s what I need to upgrade to.  I know PTGUI is not designed for this but the Ver. 11 was working much better.

Best,

Spike

[Spike Mafford]

Here is a sample set of images I used for a composite file.  There are 24 images in the series in an effort to create a 20,000  x 20,000 pixel file of the original art.  The original files are 5434 x 7229 pixels, created on an H5D-40 Hasselblad.

I am including screen shots of my process and the project file as well.

[John Houghton]

Spike, The images are not an easy stitch as there is a general lack of detail that PTGui can recognise as candidates for control points. Your project file has no control points between some images and has a lot of points on the board in the background around the edges which I removed as they are on a different level and therefore create parallax issues.  I had to zoom right in and search for tiny specs and blobs to get an adequate number of points actually on the surface of the artwork.  This takes a lot of time!  But a not-too-bad result was eventually obtained, and can probably be improved with a bit more work.  The revised project file is attached.

John

[John Houghton]

Spike, I Tried to improve the result by generating additional points targeted with the "Generate points here" option and also applied viewpoint correction for good measure.  It's improved it somewhat.

John

[Spike Mafford]

Thank you very much for the research in to the problems I’ve been having.
I had deleted all control points and then added them in, per image pair but, somehow couldn’t get to the point of generating the project without it reverting back to auto generated points. Once you add points manually, you have to optimize, prior to creating the “final” panorama. What is the work around for this?
I spent many hours adding points, only to lose all the work, multiple times.
These are a unique style of painting and, I too, was using the hairs and dust on the surface, as control point locations. Dumb luck to have started the project with these three smallest works. I am encouraged to try again with other pieces. I believe the method for capture is sound, having seen the results you achieved.
Thank you for restoring my faith in PTGUI!
Best regards,
Spike


Spike Mafford
206.719.337
Zocalo Studios, LLC

[Erik Krause]

Am 20.08.2022 um 16:33 schrieb Spike Mafford:

> I had deleted all control points and then added them in, per image
> pair but, somehow couldn’t get to the point of generating the project
> without it reverting back to auto generated points. Once you add
> points manually, you have to optimize, prior to creating the “final”
> panorama. What is the work around for this?

Apparently you pressed "Align Images". Don't do this, Press F5
(Optimize) instead. "Align Images" will start from scratch and generate
control points automatically.

> I spent many hours adding points, only to lose all the work, multiple
> times.

As for all computer work: save frequently! You can also undo recent
steps by pressing Ctrl+Z (windows) or Command+Z (Mac). PTGui even tells
you what it will undo in the Edit menu.

[Spike Mafford]

Thank you Erik!

Spike Mafford
206.719.3378
Zocalo Studios, LLC


> On Aug 20, 2022, at 8:13 AM, Erik Krause <erik....@gmx.de> wrote:

> --
> 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.
> To view this discussion on the web visit https://groups.google.com/d/msgid/ptgui/98908081-bc13-53f1-5fa8-03eadbedeb4a%40gmx.de.

[Spike Mafford]

Hello John,
Is there a tutorial on applying “viewpoint correction “? Also, would adding vertical or horizontal points(not sure how to do this either), add to the quality?
Thanks,
Spike

Spike Mafford
206.719.3378
Zocalo Studios, LLC

> On Aug 20, 2022, at 8:20 AM, Spike Mafford <spikem...@gmail.com> wrote:
>
> Thank you Erik!

[John Houghton]

Spike, Viewpoint correction tends to be discussed in connection with patching nadir shots into a 360x180 panorama to cover up the tripod.  The nadir shot may be taken well away from the rotation point of the main set of images and therefore requires correction for the different viewpoint.  But if you have a set of shots all taken from differing viewpoints, then you can correct each of them with control points created only on a single flat plane like a wall or floor or ceiling (but leave one image not viewpoint corrected as a sort of anchor).  The viewpoint shots must have objects outside of the plane masked out (like furniture poking up from the flat floor).  

For your panorama, you just have the flat plane of the artwork (excluding the flat support surface behind, which can be ignored by not creating points there).  So there are two tutorials on the PTGui web site ("Learn"), one of which is in the videos section (Part 7).  I also have one recently updated for V12 at  PTGUI PRO -VIEWPOINT TUTORIAL (johnhpanos.com).

Horizontal and vertical line control points are invaluable for getting the image aligned with the edges properly horizontal and vertical.  They are to be created on line features that are expected to appear straight and vertical/horizontal in the currently selected projection for the output panorama.  Again, they are very relevant for levelling 360x180 panoramas, so tutorials tend to be aimed in that direction.  There are tutorials on the PTGui web site and there's and old one of mine at  LEVELLING A PANORAMA IMAGE WITH PTGUI (johnhpanos.com).

Levelling won't make any difference to the stitching quality of the panorama. OTOH, I did make use of straight line control points for your panorama to get the edges hopefully glitch free.  You can create points of type "Line 1" along a line feature possibly crossing several images in order to encourage the optimizer to get the points into a straight line (in the currently selected output projection).  Do the same for other straight line features, using Line 2,  Line 3,  points for each successive line.  Just select "New line" for the control point type.for each new line feature required.

In the current project, I found it necessary to create far more special points than I would normally expect to do, largely because of the bland images devoid of detail for control points.

I would also add to Erik's suggestion that it is much more straightforward if you simply photograph using a long lens with the camera mounted on a spherical panorama head, which rotates the camera about the entrance pupil of the lens (AKA no parallax point) to avoid parallax issues.

John