Wim van Egmond wrote:There are details lost because of the jpeg compression. I am not sure if there are ways to improve this.
First, check to be sure that the loss is actually due to JPEG compression and not due to resizing. In Photoshop there is a Preview checkbox that can be toggled on and off while you are adjusting the compression quality. If this preview shows details getting lost, then your problem is definitely in JPEG compression. Otherwise, detail may be getting lost at an earlier stage, perhaps in the resizing.
Within Adobe tools, the only techniques I know to reduce or avoid lost detail are to 1) sharpen before saving, and 2) use "Save for Web" as opposed to "Save As". The first approach may avoid low contrast detail being discarded. The second removes some overhead in the files, which frees more space for image content. There may also be some difference in the compression algorithm; I don't know for sure about that.
I ran a test just now where I started with your third image (size 298,086 bytes), then resaved it to be Save As quality 4 at 106,607 bytes, Save For Web quality 46 at 105,248 bytes, and Save For Web quality 41 at 104,705 bytes after USM 50% at 0.7 pixels. The last one lost some of the fine striations in the wide area of the gullet (?), but other than that I can't see any detail loss despite file size being over 2.5 times smaller. The Save As quality 4 lost a significant number of the fine striations.
--Rik