What is standard image size?

I want to create a Slideshow with several photos and videos.
In preparing the photos/videos, I can edit them so that they're all a standard size.
My question therefore is as follows: what is the standard size that I should use for the dimensions (heigth/width) of each photo and video?
Thank you in advance for your help.

Hi
there is no "standard" as you can set the image ratio in the module settings.
The best solution is to have the same ratio (height / width) for all images. You can use the "info" icon in the module settings to calculate your ratio
CEd

Excellent. Thank you very much for suggesting using the same heigth/width ratios and for using the 'info' icon.