In this video by Vladimir London, a Life Drawing Academy tutor (https://lifedrawing.academy/), you will find out the ovals rules and common mistakes. Let's begin with the rules.

A circle in perspective will appear as a perfect elliptical oval. It has two axes perpendicular to each other. Here's the 90-degree angle. The part "A" above the main long axis is shorter than the bottom part "B". This is because we see this circle in perspective from above or below the horizon. Because the top and bottom parts are not equal to each other, such an oval is not symmetrical across the long axis. However, the top and bottom left and right parts, marked here as "C" and "D" are equal to each other and therefore the oval is symmetrical across its vertical short axis. Also, note that the bottom outline of this oval, which is closer to a viewer, is bolder than the top outline, which is further away. This follows the rule that the objects that are further away will be seen closer to the horizon, and appear smaller than those objects that are closer to a viewer. This rule also applies to the thickness of lines. So, we know that this circle in perspective has a perfect elliptical shape, is seen below the horizon, it is only symmetrical along one axis and its frontal part is bolder than the rear one.

Now, let's talk about common mistakes. An oval must have an elliptical shape and be symmetrical along its short axis. This drawing does not follow these rules. Another mistake beginner artists often make is drawing sharp ends of an oval. Circles do not have corners, neither do ovals. Another similar mistake is drawing not sharp, but pointing ends. An oval must be elliptical. Here's another example of an incorrect oval with blunt or squarish ends. I hope you will avoid such basic mistakes when drawing circles in perspective.

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