I love teaching about Op Art! The kids get really excited and love looking at all of the examples and what's even better...they like to discuss them! I don't even have to prompt them into having a conversation about it, they automatically start the discussion as soon as I show an example! It's amazing! Last year I taught the fifth graders an amazing cube optical illusion (lesson here) but this year I wanted more variety and to teach them a little more about shading. So I gave them a series of options in their illusion. They all started with 3 circles (though one of my examples below only has one big one) and then they chose their style of background. They could do "cones with draping ribbon," checkerboard or a checkerboard fading back into space:
I demonstrated all of the steps (full lesson details for the fading into space plan are here) for drawing out the backgrounds and let the students get to work. I showed them how to make their circles have the illusion of spheres and had them color in their background and spheres like checkerboards (or color in the "ribbons" along the "cones"). My example used a black marker for this step but some of them opted for color. After that had been finished or nearly finished by most, we discussed shading and how to shade based on the chosen background. The kids were all great about knowing that with the distance/checkerboard background, the smaller tiles were darker because they were farther away--and I love that they know that! So smart! After that, they finished coloring them in with colored pencils and appropriate shading!
Since students all work at a different pace--some students didn't quite finish and others had tons of free time. So I suggested that they use their 'finished early' time looking at Optical Illusion books that I have on hand, drawing a simple optical illusion design with their name (I demo this and how to do this with a wavy line instead of their name) or to try to draw their own optical illusions that they create from their brain!