Light foreground changing exposure of Milky Way panorama

[Chris Slaybaugh]

I'm trying to composite a Milky Way panorama using PTGUI pro13.3. Image consists of 22 sky images and 6 foreground images. The sky is, of course, fairly dark. which I want. The foreground is quite a bit lighter, by design (longer exposure at higher ISO).

In order to preserve alignment between foreground and sky, I combine all the images in PTGUI, perform alignment, then by deselection/reselection, create separate panoramas of foreground and sky for later combination in Photoshop. While this gives me tiffs of each in perfect register (vital!), the sky panorama becomes much lighter than it should be. If I create a similar sky panorama from scratch, using just the sky tiffs, it is much darker, as it should be. But of course in this case, the register is off and I have a hard time compositing.

I've turned off all the exposure-related adjustments I can find, but can't get the sky-when-aligned-at-same-time-as-foreground to come out as dark as the sky-when-aligned-alone.

How to I keep PTGUI from brightening the sky when alignment includes brighter foreground images?

(FYI, I have not had success using template features to do this. And while I could re-darken the sky in Photoshop, the whole idea is to minimize adjustments to preserve image quality and accuracy. Lastly, I've asked ChatGPT, which thinks PTGUI has many additional exposure options exposed than I am able to find. )

Thanks!

--Chris

[PTGui Support]

Hi Chris,

Are your foreground images taken at a different exposure time than the
sky images? By default PTGui applies exposure compensation, to bring all
exposures to a 'middle' exposure prior to blending. That could explain
what you are describing.

You can switch this off in Panorama Editor - Blending - Exposure
Compensation.

Or alternatively you can apply an exposure offset in Panorama Editor -
Post Processing.

ChatGPT hallucinates terribly, it doesn't have much PTGui knowledge in
its training data. Better ask here!

Kind regards,

Joost Nieuwenhuijse
www.ptgui.com

> --
> 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
> <mailto:ptgui+un...@googlegroups.com>.
> To view this discussion visit https://groups.google.com/d/msgid/
> ptgui/9b5a9082-916e-4791-b84b-3c9f7da50ceen%40googlegroups.com <https://
> groups.google.com/d/msgid/ptgui/9b5a9082-916e-4791-
> b84b-3c9f7da50ceen%40googlegroups.com?utm_medium=email&utm_source=footer>.

[Chris Slaybaugh]

Thanks, Joost--that helped a lot!

 " Are your foreground images taken at a different exposure time than the
sky images?"

Yes, the sky images were taken at 60 seconds, ISO 500, f/1.4; the foreground images were 180 seconds, ISO 1250, f/1.4--so very different exposures. This was because I didn't want to burn out the very bright stars in the sky, but also wanted a lot of detail in the foreground, which was lit only by starlight and airglow.

Following your advice, I now have nicely exposed composites of each, and am combining them in Photoshop.

Very best regards,

--Chris