Hey there! First of all, great job on the overall values, the brightness already resembles the reference quite well! Two things I'd like to suggest: 1. To make your light side look more like the reference, you might want to use less of the highlight value. Especially underneath her lit cheek, you might have overused the value a bit. This causes the highlights (like the temple or the cheekbone) to not stand out anymore, because the areas are basically on the same level. 2. Soft edges: I don't know if it's for the sake of the value study, but there are a lot of hard edges you painted (which is valid to be able to focus on value only). This also adds to your issue about looking flat, because edges play a huge part regarding volume and believability. Faces are very delicate when it comes to this, so you might want to add in a softer brush or play around with a smudge, like I did, ever so often. I hope this helps and keep up the great work!
