QuickTime: HD video displayed too large on MBP M5 Pro screen and HDMI screen.

With a high-resolution display (the Retina display in MBPs, some external displays), macOS renders the screen images at twice the physical resolution. For example, on my MBP in clamshell mode, the LG 5K:2K display that is set to 3360 x 1418 is internally rendered at twice those dimensions, as you can see from a full screenshot.

In QuickTime Player, the Actual size and Zoom to fit commands are only available after you select Zoom in.

You can use the commands and shortcuts in QuickTime Player > Window menu to adjust the displayed size of the video.

Something does not add up.

Can you show us what the display settings are for your Dell display, and also an Info window for a full screenshot of that same display, similarly to what neuroanatomist showed?

This would help us understand the math...

It seems that your display is set to some "retina" resolution.

Also, see my screenshot below.

In the Displays section of System Settings, activate "Show resolutions as list";

then for the display in question, activate "Show all resolutions". Show us what you see.

Your display may be set to a retina resolution.

Did you mean 3840x1600 (that would be roughly 21:9 aspect ratio, not 3340)?

Ernest House wrote:

I just jumped from MBP 2018 on Monterey to MBP 16" M5 Pro with Tahoe. I generated an HD video from FCP 12 using the Apple HD preset. However when I open the HD video on a Dell U3818DW 21:9 main display (3340x1600) that has a PPI of 111. The video window size is noticeably larger than when on Monterey using the same display. Quicktime Player reports the same HD resolution for the video resolution and "Current Resolution":

https://discussions.apple.com/content/attachment/5d10c52c-bff8-4571-881b-3ffdc72274b7

On a lark, I dragged it onto the MBP screen. As expected, it is too large for that screen (a true 1920x1080 video should fit just fine). Once on the MBP display, the Quicktime Player reports a much larger "Current Resolution."

https://discussions.apple.com/content/attachment/693863df-fe86-41f0-a65c-44a63f304c62

Quicktime in Tahoe no longer has the convenient hotkeys to change the display to half size. Using the "Actual Size" command is not selectable on either screen nor is Zoom to fit.

The change in "Current Size" is due to your built-in screen being "Retina", whereas the Dell is not.

(As you probably know, "Retina" resolutions are typically nominally half the physical number of pixels, but text and video is rendered using full resolution, that is how you can get the smooth display without it being tiny).

I see this too; I just keep the Movie Info window open as you drag the video from one display to the other and the "current size" instantly doubles or halves - again, this is expected.

Did you press Command-0 for "Actual Size"?

You could also press Command-F to view in full screen. This should scale to full screen regardless of the movie dimensions.