so clearly without doubt I am not as good as drawing as you are, this took me 20 minutes and the anatomy is all off. But I cant put into words clearly what I want to point out, and I loved the face of your model so I made a copy of your drawing. Here is what I see off. Your shading is off, you put too much emphasis in making difference in each anatomy part, I personally notice it in the abdomen area and the ankle: I am not sure where your belly button is, but I imagine it should be around that drape its wearing, but since you made so much emphasis on the dorsal muscles it looks like the (chocolate bar) abdominal muscles are off center. Also, the muscles below that drape should be darker. This is where I learned this from Proko and Gonzo, the values are important. See my image? I made a 4 value grid. 1 black, 2 grey. 3. light grey. 4 white. obviously since my drawing is bad my shading is bad, but bear with me... I shaded in 4 that part of the body, the muscles below the drape, and if you want to make the muscles popup, maybe choose a 2. and on the other side where the light hits, the muscles shade it with 3. so in the dark muscles are 1 and 2, in the light 3 and 4. Makes sense what I am saying? the ancle is similar, you made the figure of the bone protution in the ancle truly pop up beatifully, but forgot to shade that area, and sometimes you loss lines when you shade. Also, the shadow of the hand and of the face are in complety different dirrections. I shaded the head, but i didnt know where to shade the hand so i didnt in my drawing. but yours is a diagonal in the head and a vertical in the hand over the leg, and that doesnt fit. What do you think of my opinion? I am not as good as drawing as you so I hope you dont get offended. we can help each other.

You're welcome, @Jesper Axelsson! About this question, my take is that there can be various ways to approach values in practice, and it mostly depends on your goal. If you want to train observing values more accurately, it can be helpful to copy the exact values you see; but if you want to do an intentional application of values in a composition, you can tweak, change and design as freely as you wish and are able to without worrying about straying from the reference. If you're drawing on an "off-white" toned paper (almost white, but not quite), you could use things such as white gouache or acrylics or a white marker to put in the strongest highlights without having to tweak the whole value range. Another thing to keep in mind is that all materials have specific limitations and this often requires deliberate concessions: graphite pencil, for example, might not go as dark as charcoal - so if you want to shade something black, but for whatever reason, you only have graphite to draw with at that time, you'll have to settle with the darkest dark your graphite gives you, even if you're aware that what you're seeing isn't that exact value. Hope this helps! :)

Hey, Jesper, good question. I'm no sure if my thoughts about this are in consensus with what other artists think, but I'll share anyway. I think it's always about relationships. If you're painting with a full-value range and you have 10 values to work with, then you can say 1 is black, 2 to 4 are dark grays, 5 and 6, middle grays, 7 to 9, light grays, and 10 is white. You could also be painting with a full-value range, but only have 5 values to work with, then you'd have only one value for each gradation: 1= black, 2 = dark gray, 3 = middle gray, 4 = light gray, 5 = white. In the same way, you might take the 10-value scale and turn it into a 20-value one by adding "in-between" values, then you would have 1 as black, 2 to 7 as dark grays, 8 to 13 as middle grays, 14 to 19 as light grays and 20 as white - or instead, if you prefer, you could keep the same original numbering and call the added "in-between" values 1.5, 2.5, 3.5... The numbering for itself is merely conventional and contextual, and it's only important as long as it helps you, the artist, to better understand how to organize the values in your painting. But, in the end of the day, what really matters after all is how the value relationships are visually applied in your composition. Personally, I prefer to think in terms of range (lights, darks, middle...). But if you like working with numbered values, I'd say having a basic 1-to-10 full-value scale in your mind as a parameter might be a good general "rule of thumb". Hope this helps! :)