Dreamstime's requirement page is unusually explicit. All files must be uploaded in JPG format, RGB and sRGB, free of noise or any other artifacts, with a minimum size of 3 MPs and a maximum of 70 MP. It also pre-empts the exact mistake this page exists for: it tells contributors not to confuse MP, which stands for photo dimension, with MB, which stands for file size on disk, and shows the arithmetic — multiply length by width in pixels and divide by 1,000,000, so a 3000 x 2000 file is 6 MP. The 70 MP upper bound is generous enough that almost nothing hits it from a normal camera, which means the real constraint here is qualitative, not numerical: free of noise or any other artifacts. That phrase is a direct instruction about how hard you may compress. A file squeezed to the smallest possible byte count develops blocking and banding, which is exactly the artifact class the agency rejects. So the compression target for Dreamstime is not a byte number at all — it is the point just before artifacts appear. Move the quality down in small steps, inspect at 100%, and stop at the first step where smooth gradients start to band.