Originally Posted by AnemicOak
While I agree there are lots of covers out there that are a larger file size than needed. With current cover specs required by many retailers (1400 pixels minimum width and likely to increase over time) 100kb or less isn't realistic for many of the images out there.
I've seen one ebook from Apple where the cover image was close to 90% of the book size. Yes, it looked better when I looked at the cover image on my iPad but overall, was the change worthwhile? Not really since I really don't spend much time gazing at book covers.
Just for the heck of it, I converted a 4000x6000 image of decorative cherry blossoms to a 1400x2100 image. Dropping the jpeg quality to 75% when saving gave me a 185KB file. The original image clocked in at 13.4MB but then the camera is set to maximize quality when saving .jpg format -- I have to justify having dual 32GB cards in the camera somehow.