Test SrcSets

Original images (size in the caption) tested on various devices, like an iPhone XR (828x1792), iPhone 13 Pro (960x2079), iPad(1548x2064)  (PC Monitor (2560x1440), 4k Laptop (3480x2160).

If you open an original low resolution  image in portrait mode  with the Chrome or Edge browser under Widows  you see initially with the original images  a problem background, see lightGallery issue #1521. You don't see this issue if you use FireFox or use a mobile device.