An amateur critique for a talented artist. This can only end well, I’m sure.
I'll preface this by commenting on the dA star rating system, which is a really dumb system, but I tried to be honest within its context. Most of this is explained in the longer section of text below, but just a quick overview first.
Vision (4.5): Generally well-executed idea that still has a few polish points that are more than simple nitpicks.
Originality (4.5): I wavered on this one for a while. As a standalone piece, considering none of your other art, it's quite original: braces, shiny pony, teenager—it's an excellent blend. However, in the context of your recent work, it's a different take on the same idea. It's still interesting (and adorable!), but it's been done (obviously). I decided to split the difference. As a standalone execution, this merits 5 stars. In the context of your recent set of portraits (especially those with braces), it merits 4 stars.
Technique (4.5): You know your way around an airbrush and your layer settings, and it shows. Certain aspects (detailed below) could be easily improved upon, but it's a solid execution overall.
Impact (4.5): The half point being docked here is due to the eyeshadow color contrasting with her force of personality, not her coloration specifically. Again, this is detailed below.
Before I discuss the shading, most of your form seems fine. However, the horn appears to be angled up too steeply, as I’d expect it to be jutting out along the normal vector at that contact point on her forehead and foreshortened accordingly.
You have a balanced amount of darks and lights throughout the piece, and your composition takes advantage of that in specific places to good effect: her neck falling beneath her fringe pops because of the contrast. Similarly, the ribbon stands out against the variegated background not only due to color contrast, but also due to value differences. It’s a nice touch that helps bring her forward in the painting.
Your choice of specular highlights to make her appear shiny is par for the course, and I don’t think there’s much to complain about there. It’s not what I’d consider true-to-life going from show style to more 3D-oriented, but it’s an obvious style choice that doesn’t grate on the eyes. However, due to that same reflective nature, her fringe leaves me with an uncertain impression on whether her hair is partially translucent (and thus some of the implied shapes might be her obscured eye) or just reflective and darkened due to the hair’s curvature right there.
Worth noting is something that several people have taken stances on already: your choice of her eyeshadow color. With the disclaimer that my color theory should be taken with a grain of salt, based on this comment by WhiteHeather ( [link] ), a more appealing choice would be something that more closely matches her eye color. While this is obviously a younger Rarity, the impression we’re left with here is that despite her braces, she still has a firm grasp of her own beauty and charisma, and has the force of personality to back it up; she doesn’t come off as an awkward teen that doesn’t know what colors work best with her. The color of her ribbon, as noted before, works rather well with her coloration. The braces are, perhaps, the best of the limited options available to her.
The shading overall is good, though it doesn’t appear to define any amount of the inside of her ear, leaving it looking affixed upon her head, rather than an organic part of it. Also, based on your primary lighting (indicated by the specular highlights in her eye) and the secondary lighting (indicated by the yellow–yellow-green highlights across various parts of her face), the join point of her ear and the curve of her upper cheekbone should be darker, but it appears to be getting some sort of spot lighting there from nothing that seems discernable in the scene.
In regards to her bow, the inner loops appear accurate based off of the primary light source, but the outer loops have odd spots of shading that don’t seem to belong on the side facing the light source—there isn’t ambient occlusion on the convex side of the ribbon for it to grow darker so close to the highlight. Some of the spirals on the ribbon suffer from this as well.
The lack of shading on her face from the nose to cheek area doesn’t give us vital information on its depth—the value from the front of her nose to her cheekbone is essentially the same. Above her eyeshadow, you used a faint blue–blue-green shade to good effect—it informs us there’s a slight recess there and isn’t just a result of ambient occlusion due to the eye’s proximity. I believe that this same type of subtle shading would be good around the lower edge of her eye (and coupled with a highlight, which appears to be missing above the brow) to help give her face more depth.
The number of specular highlights on the eye make it difficult to tell whether the iris highlights are being portrayed correctly, but there’s enough incidental lighting that I don’t know that it’d even be visible. Her eyes are fantastic, and I think the fact that you dialed back some of her eyeliner really does a service to making the eye stand out (in a good way) as much as it does.
Your lighting on the hair is excellent within the context of your shiny style, and it does a great job of helping the hair display not only its volume, but its shape and bounce. I feel like it could be darker where it curls behind her ear, where it’s occluded by her head, but that’s it, really.
All in all, an excellent job. In the context of improving, I think that choosing a different pose and expression would be good—what you’ve done here is well-executed, but it’s also well within the bounds of what you’ve done before. It’s safe, it’s familiar, but it could be more interesting, both for you as the creator, and for us as your audience.