I’ve been playing with JPEG output quality on some old 6 meg files from a Canon 50D. At 10% output, the file size is only 400K , but the quality is very poor; Pixelated and posterized; so poor I wonder why it’s even offered as an option. However, when 50% output is compared to the normal 90%, the quality differences can only be seen at 400% magnification and they are not bad; slight artifacts on the edges of lines and posterization that takes a critical eye to see. Furthermore, file size is only 1 meg.
Storage is cheap and plentiful, so file size is not an issue, but performance, particularly with older computers is an issue: smaller files process more quickly. Why do we output at 90% when 50% is adequate for all but the most discerning eye?