No worries - it's perfectly okay to just take pictures of your work, rather than scanning it. In some cases I prefer it (but mostly because some students mess up their scanner settings - yours are fine though).

Anyway, congratulations on completing the challenge! I'm very pleased to see that you played a lot with the rates of foreshortening throughout your first set (the cylinders around arbitrary minor axes), and I'm also pleased to see that you were very fastidious in checking the alignment of your ellipses. This kind of analysis definitely yielded improvement - although there's still room for growth here, and that will come with practice. In particular, the wider ellipses tend to be somewhat trickier to align.

Now, across this first section, there is one key mistake that I'm noticing on occasion, and we can actually see it fairly prominently in cylinder 150. Foreshortening manifests in two distinct ways, two distinct "shifts" between the end closer to the viewer, and the end farther away. There's the obvious shift in overall scale, which occurs because of the convergence of those side edges making the farther ellipse smaller than the end closer to the viewer. Then there's the shift in degree, where the farther end is going to be wider than the end closer to the viewer.

Both of these signs tell the viewer that the cylinder they're looking at has a length that is more than just what they see on the page. After all - if your cylinder is running parallel to the picture plane, then the physical length we see on the page is how long that cylinder really is. But as soon as you start tilting that cylinder towards the viewer, or away from the viewer, some of its length will exist in the "unseen" dimension of depth, which we cannot directly capture on the page. So instead, we use foreshortening to imply that there's more to its length. A little foreshortening tells the viewer that the length of the cylinder is a little longer, whereas a lot of foreshortening tells us that we need to take that visible length and multiply it by a more significant factor.

The problem arises when these two shifts suggest different amounts of foreshortening. If we look at cylinder 150, you've got a significant shift in scale - the far end is much smaller than the closer end - but the shift in degree is minimal. So if we look at the shift in scale, there's lots of foreshortening, but if we look at the shift in degree, there's only a little. This becomes a contradiction - is the cylinder shorter, or is it longer?

To put it simply, make sure that these two shifts occur in tandem - that you apply roughly the same amount in each the scale and degree shifts. You don't have to be exact, and being aware of this is usually enough to correct the mistake.

Continuing onto your boxes, these are similarly well done, with one little issue that may have hindered you somewhat. This exercise is all about constructing boxes that feature two opposite faces which are square in proportion - specifically about developing the student's instinctual understanding of 3D space to be able to achieve those proportions regardless of the box's rotation.

We achieve this similarly to how in the box challenge, we gradually built up your ability to draw lines that converge together consistently - we make a page of attempts, then we apply an analysis to find where we were off and by how much, so we can adjust our next attempts accordingly and repeat the process.

Here, the cylinders themselves - or rather, their ellipses - are part of that analysis. By checking how close they were to being circles in 3D space, we can also check how close the plane that encloses them was to being a square in 3D space. We do this by extending all three of each ellipse's lines (the minor axis and the two contact point lines), seeing if they converge consistently towards the box's own vanishing points.

Now, you've done a pretty good job with this and I can clearly see improvement over the set that will really come in handy in the next lesson - but there's one thing that held you back a little. It seems like you were only extending the two contact point lines, and didn't extend the minor axis, which ought to have been running down the length of the cylinder.

This doesn't mean the whole challenge was a waste - because of the first section you were already paying attention to the alignment of those ellipses and the direction of the minor axis, but neglecting to extend it could definitely have left you open to errors on that front that went unnoticed.

So! Simply be sure to extend all three lines for each ellipse when doing this exercise in the future.

I'll go ahead and mark this challenge as complete.