After grading an equirectangular image a seam is visible in PTG Viewer

[twalp]

After exporting gigapixel jpeg equirectangular images from PTG, I do non-destructive color and exposure editing in Affinity Photo 2.6.5. I export the result to JPEG and view it in PGT Viewer.  If any of my adjustment layers affect the entire image there is often a visible seam where the two edges meet.  Is there a way to avoid or fix this back in PTG?

[Matthew Rogers]

The problem is, most of the tools in Affinity Photo aren’t 360 aware. And now it’s owned by Canva the chances of it ever being supported are virtually zero.

Matt

On 25 Mar 2026, at 21:29, twalp <trw...@gmail.com> wrote:

After exporting gigapixel jpeg equirectangular images from PTG, I do non-destructive color and exposure editing in Affinity Photo 2.6.5. I export the result to JPEG and view it in PGT Viewer.  If any of my adjustment layers affect the entire image there is often a visible seam where the two edges meet.  Is there a way to avoid or fix this back in PTG?

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[John Houghton]

One way of dealing with this problem is to make a temporary copy of the image that is more than 360 degrees wide, do your adjustments, and then shrink the image back to 360 degrees wide.  E.g. you might copy/paste a section from the left hand side of the image to the right hand side, and likewise copy/paste the right hand side to the left hand side.  Or copy/paste a larger selection to one side, and after doing your image adjustments crop the central portion to the original width and do a shift with wraparound to restore the original centre point.

John

[Erik Krause]

Am 25.03.2026 um 22:29 schrieb twalp:

> If any of my adjustment layers affect the entire image there is
> often a visible seam where the two edges meet. Is there a way to
> avoid or fix this back in PTG?

One way to avoid this is not doing adjustments that act locally. I'm not
familiar with affinity (yet), but anything that acts on shadows
differently than on highlights might cause this effect. Only adjusting
global exposure, contrast or gamma should not cause it.

Recent versions of affinity used to have a spherical mode, where you
could edit panoramas seamlessly.

In recent versions of PTGui pro you can try to use the Patch tool. This
might be difficult for highly structured areas, though.

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

[twalp]

So what photo editors ARE 360 aware? (I didn't know about this issue until now, but it makes sense. Doh!)

[PTGui Support]

There's one way to work around this: Take your 360 image and extend it
at at the left and right hand side by copying a part from the opposite
side. So you then wider image with some parts repeated at both ends.

Then do your editing, and afterwards crop the image again to the
original dimensions (360 degrees horizontally).

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

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[twalp]

Thank you to all who responded, especially John Houghton and Joost whose answers led me to a solution. 

I tried copy/paste in Affinity Photo 2.6.5 to produce an expanded width image, but the resulting "extensions" differed in color or tone from the original image. Total bafflement, because I had done nothing to the equirect out of PTG other than view it in PTG Viewer. (no seam evident) The color space or whatever must change in the copy/paste process.

BUT, duplicating the original image to a second and third layer, deleting all but a 500 px end strip (left end and right end), and then moving the end strips to the opposite ends of the original image did produce a seamless working image. I beat the heck out of it with adjustment layers, masks, and local/global whatnot to challenge the result. I then used Resize Canvas with it pinned to the center to restore it to an equirectangular image, and exported it. The result plays perfectly in PTG Viewer. 

However, using my 32GB M1 Max MacBook both the copy/paste and the dupe/move processes with a 50K by 25K image are exercises in spinning beachball (busy indicator) watching. Being ignorant about projections and other tech details I'm curious if PTgui can create a 370 X 180 cylindrical image that can be converted to a spherical image later.