This Galaxy S21 camera guide explains how to set photo size on Galaxy phones including Galaxy S21, S20, S10 and S9, how to use the Gallery app to resize photo size on these Samsung Galaxy phones, and how to revert back to the original photo size.
How to set photo size on Galaxy S21?
In the old Camera app, you can set different sizes (resolutions) for the photos to be taken, as in the Galaxy S7 Camera app. If the storage is limited and you mainly share the photos through social media, you can choose a smaller photo size (lower resolution). Of course, if you may need to print the photo or view the photo on a large screen (e.g., an 8K TV), you should choose a higher resolution.