Landscape Astrophotography - Layer Blending in PT Gui v Auto-blending in Photoshop

[Hugh Brown]

Landscape Astrophotography - Layer Blending in PT Gui v Auto-blending in Photoshop

What are the advantages of doing layer blending in PT Gui during the stitching process and exporting the blended file versus exporting individual layers from PT Gui and then bringing those layers together as an auto-blend in Photoshop?

And what are the disadvantages?

One of the disadvantages of the former approach that comes to mind is difficulties rectifying horizon steps after the stitch in PT Gui if the stitch is exported as a blend.

[PTGui Support]

Photoshop's auto blend and PTGui's zero overlap blender will probably
give similar results.

If you see horizon steps, that's probably something that should be fixed
first though. Most cases of misalignment are caused by parallax. Did you
use a panoramic tripod head?

It could also be caused by moving objects (likely the stars), in that
case stitch the ground panorama separately from the sky panorama. The
ground panorama should have no errors at the horizon, assuming you did
use a panoramic tripod head.

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

On 8/3/26 00:41, Hugh Brown wrote:
> *Landscape Astrophotography - Layer Blending in PT Gui v Auto-blending
> in Photoshop*

>
> What are the advantages of doing layer blending in PT Gui during the

> stitching process and exporting the blended file *versus* exporting

> individual layers from PT Gui and then bringing those layers together as
> an auto-blend in Photoshop?
>
> And what are the disadvantages?
>
> One of the disadvantages of the former approach that comes to mind is
> difficulties rectifying horizon steps after the stitch in PT Gui if the
> stitch is exported as a blend.
>

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[Erik Krause]

Am 03.08.26 um 00:41 schrieb Hugh Brown:

> What are the advantages of doing layer blending in PT Gui during the

> stitching process and exporting the blended file*versus* exporting

> individual layers from PT Gui and then bringing those layers together as an
> auto-blend in Photoshop?

Before PTGui had Zero Overlap Blending and Optimum Seam, PS Autoblend
Layers was superior, in that it routed seams around objects and
performed a good equalization of brightness and color in adjacent
images. However, it didn't blend across the 360° seam. I even wrote a PS
script to circumvent this:
https://erik-krause.de/ttt/#AutoBlend360Javascript
But PS didn't blend across zenith and nadir either. No idea whether it
does now, I never upgraded to the subscription model.

PTGui has resolved both of these issues by introducing Optimum Seam and
Zero Overlap Blend, and the Patch Tool has also reduced the need for
external editing.

However, since astro shots are a bit different in that the features are
point-like, surrounded with black (or rather: light pollution :-( )
Optimum Seam and Zero Overlap might give inferior results compared to
other blending solutions. Hence, the answer is: it depends. But you have
more options inside PTGui to try: Optimum Seam can be switched off and
combined with three different blending options. So you will have to try
on your own what the best solution is.

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

[Hugh Brown]

Thanks Erik.

The problem with getting PT Gui to do the blend is that the row is one of two and so all the images have been ingested into PT Gui and then outputted as individual layers because PT Gui can't - and should not be expected to - handle the exposure differential between the blue hour (ie, much lighter) foreground and the darker sky.

There is a second issue also.  That the lens I have been using has sharp fall-off in the corners when shot at f2.8 (ie, fully open).

This means it creates vignettes and which I need to remove via the creation of manual masks in PS before I do the auto-blend.

I'm sure there is a simple solution to this - I've not yet been smart enough to solve it.

Cheers.  Hugh.

[Erik Krause]

Am 07.08.26 um 02:21 schrieb Hugh Brown:

> The problem with getting PT Gui to do the blend is that the row is one of
> two and so all the images have been ingested into PT Gui and then outputted
> as individual layers because PT Gui can't - and should not be expected to -
> handle the exposure differential between the blue hour (ie, much lighter)
> foreground and the darker sky.

It can actually. There are three ways: If the correct exposure is in the
EXIF data, you can try to just check Exposure compensation on Pano
Editor Blending side menu. Or you can go to Exposure/HDR tab and enable
Brightness optimization under Automatic exposure... -> Settings. Both
possibilities will likely darken the brighter and brighten the darker
images. If you don't want this, you can enter an exposure offset on
Image Parameters tab Exp. offset column manually (you can select
multiple fields). If this renders the landscape too dark, play with Tone
mapping or Exposure fusion settings in Pano Editor side menu.

> There is a second issue also. That the lens I have been using has sharp
> fall-off in the corners when shot at f2.8 (ie, fully open).

Paint a red mask for one image in PTGui, then go to Source Images tab,
copy the mask from that one image and paste it to the others (multiple
selection possible -> right click menu). You also can save it to disk
for later reuse.