Ideal 16:9 project size - should it really be 960 x 540?

Been playing around with this some more.

I took the same image and resized it to three different heights: 540px high, 720px high and 1080px high.

I then uploaded the image into 3 different SL360 courses - each course with slide dimensions altered to match the height of the image it was showing (so a 960x540 slide size for the 540px high picture, a 1280x720 slide size for the 720px high picture and a 1920x1080 slide size for the 1080px high picture).

I then exported all three courses as web output and viewed the picture contained in each course side-by-side in Google Chrome on my PC screen (which has a QHD (2560 × 1440 pixels) resolution).

Here's what I found:

The 540px high image (at 96kb file size) was acceptable on my QHD screen. To the trained eye, you could tell that it had lost some pixel quality but not much.

The 720px high image (at 150kb file size) showed improved pixel quality on my QHD screen. Not a massive improvement, but an improvement.

The 1080px high image (at 279KB file size) barely showed any noticeable improved pixel quality at all compared to the 720px high image.  

I appreciate that there are many other factors at play when it comes to image quality in courses (such as SL360 image export settings and browser scalability capability for example) but here are the lessons I am taking from this:

1. 540px high images on a QHD (and therefore HD screen) are perfectly acceptable unless you/your client wants or needs tack-sharp image resolution.
2. Images around 720px high offer slightly better pixel quality but images at 1080px high don't offer much noticeable pixel quality improvement at all. 
3. There is a balance to be had between image quality and file size. For hefty courses with many slides, I will consider reducing the file size of images used without sacrificing too much image quality.

I hope this helps someone somewhere!

540px high image (courtesy of Pixabay):

720px high image (courtesy of Pixabay):

1080px high image (courtesy of Pixabay):