I re-did the Mug with Onion , but this time, I used the photo as reference, copying values directly from the pic. You can see the difference by scrolling down.
Painting from photo reference does help a lot, but its always good to do a dry run live and without photos, before doing the final version with the help of photo images.
Mug & Onion re-done
6 x 7" Oil on board