SO... this is a minor issue. Just curious.

I connect to cms.waltrips.com, go to a gallery, select a picture. it foes to the image page...

Picture comes up large with incorrect aspect ratio for a split second, then resizes to correct. I click on 'next' and it does same with next picture, etc.

I do have ImageMagick. Could that be causing this? or is this normal?

I quickly looked. That's not exactly normal but I am not familiar in that detail with this theme. I assume that adjusting/resizing the image here to fit correctly within the space.

Not sure why but might be related that the image has no width/height attributes set. That could indicate that it does not use the standard template image functions which should do this.

I don't see the behaviour with the theme on the https://demo.zenphoto.org/album1/Cosmos01.jpg.html though.

Imagick surely nothing to do with tis as that is serverside and statically generates the image sizes.

If the theme option Vertical Scale Full Image is checked, Javascript removes the width/height attributes and resizes the image to be always entirely visible. This process is the glitch you see.
See the info next to the option.

OK on that. Was able to test. With it checked, it scaled to the viewport, With it unchecked, the pictures often end up larger than the available window (viewport).

Is there a way around this?

Is that with all images or just the video's?

Both.... images are not too bad. you can scroll, the I would rather not. 4k video... yikes.... Its huge

I don't mind the pause for it to resize with it checked... and If I have to will deal with it resizing in front of me. It would be more attractive if it did not resize visibly.

With this concept the theme author implemented back then there is no way to not resize visible since it needs to be loaded first before this can be done. With some rework the images could perhaps be done similar with another way but for the huge video itself there is no way around

OK... will just accept,

are there any supported themes that are close to zpbase?

No, sorry. But perhaps work on the huge video ;-)

To at least get the video's right again try this:

In your style.css lines 282-285 there's

audio, canvas, video {
  height: 100%;
  width: auto;
}

Remove the width: auto.

thanks. Will try.

Question, Is there something I can do with Thumbnails that would correct the picture resizing?

A little strangeness on the sytle.css change:

http://cms.waltrips.com/Brecksville-Reservation/Hemlock%20Loop/VID_20200913_153253.mp4

Question, Is there something I can do with Thumbnails that would correct the picture resizing?

These are no "thumbnail" type images but "sized" types. Without modifying the theme you cannot do anything here.

A little strangeness on the sytle.css change:

Not really that strange. The video images is not really a normal image but technically enclosed within the `` element becuase it is actually an attribute. Here not the image but the video element is resized.

It would be surely be better if the video image would use the same aspect ration as the video itself (using a screenshot/still)

A little strangeness on the sytle.css change:
Not sure what you did but I see that you still have line 284 (i.e. width: auto;)
Try to remove that line.

grr. though I have commented it out. however, with it out, it is still happening

Looks good to me. Empty your cache and browser memory.

still a little strange.... thumb for movie smaller... when I play it foes full size

Yeah, that's as far as I can get right now.

Sidenote @jwaltrip4 Define a rewrite suffix on the option as otherwise a page like http://cms.waltrips.com/Brecksville-Reservation/Hemlock%20Loop/VID_20200913_153253.mp4 may be interpreted wrong espeecially for SEO (it looks like a video file URL but isn't one).