All photos have their orientation in the EXIF tags. ZenPhoto is correct rotating the thumbs on the gallery and image pages, but when starting the slide show or viewing the full image it doesn't rotate photos with unnormal orientation.
You can check on https://alben.mossels.de/2021/2021_kanu/. The exif orientation for the photos in this folder are:
======== 20210721_103033.jpg: Orientation : Rotate 180
======== 20210723_182759.jpg: Orientation : Rotate 90 CW
======== 20210724_190608.jpg: Orientation : Rotate 180
======== 20210724_191010.jpg: Orientation : Rotate 90 CW
======== 20210724_191234.jpg: Orientation : Rotate 180
======== 20210724_191246.jpg: Orientation : Rotate 180
======== 20210724_191322.jpg: Orientation : Rotate 180
======== 20210724_191342.jpg: Orientation : Rotate 180
======== IMG_4394.JPG: Orientation : Horizontal (normal)
======== IMG_4395.JPG: Orientation : Horizontal (normal)
======== KarteAlle.jpg:
======== P1000003.JPG: Orientation : Horizontal (normal)
======== P1000442.JPG: Orientation : Horizontal (normal)
The ones with "Horizontal (normal)" are displayed as expected, as well as the KarteAlle, which doesn't have an orientation tag. But all others are scrambled.
Another example with a non SmartPhone photo is https://alben.mossels.de/2021/2021_kanu/210720/DSCF4304.JPG.

Is this a bug in colorbox_js or is the function called the wrong way from ZenPhoto? I've no clue how long this behavior is lasting, but it's the same in all themes, I've tried 3 or 4 for now.

Thanks for some hints how to get my albums working again.

Jan

The colorbox script just displays an image directly as it is. There is no processing of any kind involved. Most themes like the one you use this for the full original image which is as you uploaded it. So bottom line to get this to use you would have to upload them already rotated.

Off hand you can try to to set Options > Image -> Full image protection > "Protected view" as the image then will be serverd through a page. Not sure if that really rotates (have no image to test at hand right now).

"Cache the full image" may also be an option if space is not an issue.

Thanks for the tips, but both had no effect.

But I'm pretty sure it was working in the past, so I thought about options I've recently changed and was successful with "Enable Imagick". After disabling the option everything is fine again. Slideshow is working and the full image is also properly shown.

Until now I can't find any disadvantages without using imagick. What would be the benefit in using it?

Jan

Normally imagick is said to be faster and more efficient memory managment wise than the default GD graphic library. But I heard/read otherwise but as so many things it may depend on the server used and its configuration.

And it if memory serves right Imagick generally can preserve metadata within images which GD generally could not.

Colorbox is also an older script already so in any case it would be browser dependent whatever it does with images.

But it seems you found a way to get it working although I don't really understand why the graphics lib would make any difference here. Zenphoto generally works with both.