As of October 8th 2016, after roughly two years of offering free critiques, I will now be limiting my own critiques to patreon supporters ($3 or more). But don't fret - you are still welcome to freely submit your work and questions directly to the /r/ArtFundamentals subreddit to be reviewed by the community.
Over the many hundred of homework submissions I've critiqued, I've come to notice a lot of patterns in the mistakes people are making. Below are the most common mistakes made for this lesson.
The idea is that whether or not you choose to submit your homework for review, you can first go through your work on your own and catch common mistakes beforehand. It can be difficult to critique your own work, but it's an important skill to develop.
Do not go through this list while you're doing the work. It's a good idea to go through it beforehand so you know what to avoid, but after you've finished, you should set your work aside for a time, then sit down and go through this list mechanically, one by one, with fresh eyes.
The important thing to keep in mind when dealing with these ribbon-like forms is that the two edges that run along the length of the flat form must remain equidistant from one another at all times. Generally you'll draw one line, and then do your best to match it with a second. At the same time, however, being too careful when drawing a line will lead to wobbling and uncertainty - so, the focus lies on ghosting enough to get the rhythm right. It is not an easy task, and you won't nail it the first time. Always remember that - failure is certain, and necessary. What's important is that you keep heading in the right direction, not that you reach your destination quickly.
When you draw your contour ellipses, as I've mentioned in the past, be sure to draw through them two or three times before lifting your pen. This will keep them well rounded and even, which will help promote the illusion of volume when applied as contour lines to your organic form.
This mistake is extremely common. Contour lines are intended to run along the surface of a 3D form - their purpose is to describe how that form warps through 3D space. So, if the curvature and roundedness of a curve is too shallow, it won't imply much volume. If the curve comes to an abrupt halt at the edge of the organic shape, it will give the impression of a flat bottom, or a sharp edge. In this exercise, we are strictly after a smooth, rounded, organic form.
In order to achieve a rounded form, the contour curve must give the impression that it wraps around the form and hooks back around, continuing behind to where we cannot see. When drawing these contour lines as ellipses, most people get it right. Once they move to just drawing curves, they tend to come out far too shallow.
Always keep in mind that the form is rounded - accelerate the curve as it reaches the edge of the form, and overshoot while hooking around slightly if necessary. This will help you maintain the roundedness we're after, but after you start to gain confidence, try overshooting less and less.
When applying texture to your dissection, it is extremely important that you not give into the urge to scribble. At the surface, some textures may appear to be random, and scribbling may seem like the easiest way to mimic that apparent randomness, but the truth is that randomness is not something you generally find in natural textures. Most textures will abide by some hierarchy, organization or rhythm, but you may have to study it very carefully in order to find it.
Pay attention to how things are organized - if there's hair, does that hair flow in a particular direction? If there are spots or bumps, are they spread out evenly across the entire surface, or do they form groups and clusters? What kind of impact does the texture have on the silhouette of the object - specifically, how does it impact the overall shape? Rather than thinking in terms of lines and dots, try to think in terms of shapes - the shapes created by tiny shadows from raised bumps or scratches. The shapes clumps of hair make, rather than the individual strands. Focus on these things when identifying your textures, don't just scribble and hope for the best.
When applying texture, many will think that more detail is better. More little lines, little visual bits and bobs. More is better, right? Not quite. Rather than filling a space, consider the balance between emptiness and detail. When drawing, what we are doing is laying out a plan for the viewer's eye to follow. We're taking that eye on a journey through the piece, directing where it will look first, and where it will go from there. We do so by providing areas of interest (high-detail-density) and areas of rest (emptier, or calmer spaces).
If you fill a space to the brim with detail, the eye has nowhere to rest - it actually becomes painful to look at, with all of this buzzing noise arising from the high contrast of dark and light.
Instead, consider how you can group details into larger filled shapes. It isn't the presence of black, or the presence of white, that makes something distracting. It's the presence of both together, the juxtaposition and contrast of them. So, filling a shape with black will have the same impact of leaving a space blank.
Furthermore, what I've mentioned previously about the importance of a silhouette's edges stands here as well - every shape has its edges, and how those edges are crafted and cut will impact what the viewer's mind will fill into the shape. If you look at the examples below, I've cut notches into the many clusters that form into pure black areas near the edges of the form. Those cuts immediately make the viewer assume that the details they cannot see within the shapes match, but it does so without increasing the contrast and noise.
This principle is referred to as 'implying' detail. It is an art form in and of itself, and is one you should experiment with in this exercise.
Some, out of a lack of confidence or an unwillingness to think through their lines before they draw them, will attempt to sketch an underdrawing instead - either in pencil, a thinner/lighter pen, or the same pen. Then, they will carefully draw on top of the underdrawing, taking their time with slow, laborious strokes.
The result of this is lines that wobble, and forms that carry no weight or sense of solidity. Instead, draw your lines with confidence, after taking the time to plan and think through them. Previsualize the lines in your mind's eye, rather than sketching them on paper. This will improve your confidence, and will result in less waste.
You'll remember this one from the previous lesson.
This is a common issue. When you draw a single, individual box, you can apply whatever rate of foreshortening you choose. That is, the rate at which the far plane gets smaller than the near plane. Very dramatic foreshortening will have a far plane get really small very quickly. A very shallow foreshortening will have the far plane remain relatively similar in size to the near plane even if it is far, far away from it.
When you're drawing a single box, it's not terribly important. When you're drawing many boxes, however, it becomes a problem, because this rate of foreshortening needs to be consistent across all of the objects in the scene. It is a characteristic of the viewer (specifically the focal length if you want to get technical), not of every individual box. If a box has very dramatic foreshortening on it, and then the box beside it has very shallow foreshortening, the viewer is going to realize something is wrong, and their ability to infer scale will be affected.
The rule I generally use (even when drawing single boxes), is that dramatic foreshortening implies large scale, and shallow foreshortening implies small scale. A cardboard box at your feet isn't going to show a whole lot of foreshortening, but a skyscraper will.
So, when you're drawing many boxes together, as you must in this exercise, it's important to keep the foreshortening fairly shallow. You will show depth in the scene using the whole population of objects - with those far away being small and those close up being very large - instead of using each individual box. Any single box will remain fairly shallow.
This exercise is fairly new, so I will add mistakes here as I come across them.