When to use [so and so] file format? (*may* contain computer science)

Hi there.

Does anyone have some meaningful knowledge for choosing which file format for keeping detail but having decent size to store and load in a browser? In my (mine, not sure if happens to others) experience .png keeps the detail but take more time to load (assuming 1 megabyte = 1000 or 1024 kilobytes, a 1,5 MB .png takes more that 3 times to load than a 500 KB .jpg). Might have something to do with (lack of) compression, a image with lots of flat color/simple shading shoulda load faster than one with more complex coloring (for a very simplified explication, files repeat parts, to compress them one says something like "a 15 times" instead of "aaaa..."; a highly complex/already small file can't have a noteworthy compression).

If it helps, i use (very sporadically) GIMP, and the images i have are watercolor(-like).

I'm not an expert so this is probably not too helpful, but generally I find that as long as the compression level for .jpg isn't too low the quality will still be decent. I can't remember since it's been a while since I used GIMP, but in Photoshop you're given a slider to choose the compression level before saving as a .jpg. Of course, less compression leads to larger file sizes...but that's just an unavoidable tradeoff.

I've usually read that 72 dpi is sufficient for online viewing as well, so that could be another way to reduce filesize (assuming your image was originally higher dpi, like something scanned or made at print quality.)