The two optical devices that I studied the most through the reading and our class activity are the kaleidoscope and flipbooks. On one end of a kaleidoscope is a hole that you can look into and the other end allows light in. Inside the kaleidoscope, there are mirrors and colorful plastic objects that move around freely. As one looks through the hole and spins the kaleidoscope handle, the mirrors reflect the movement of the objects, forming vibrant images that constantly change. Meanwhile, a flip book is a stack of pages, each with a picture. The picture changes ever so slightly from page to page. When one flips through the pages rapidly, the allusion is created that the pictures are moving. This idea of allusion once seemed simple to me, but after reading about it throughout Jonathan Crary’s Techniques of the Observer, it is actually quite complex and intricate.

In my opinion, the observer that is being created in each of these devices is very different. On one hand, the kaleidoscope seems fascinating at first, but becomes simple once one understands the mechanics behind it. Little kids love the kaleidoscope because they don’t understand its simplicity and because, as Sir David Brewster is quoted in Crary’s book, it works “with such unexampled rapidity… [and] with a corresponding beauty and precision.” On the other hand, I think that the majority of the observers of the flipbook were well-off, white families. The flip book seems to have targeted wealthy and affluent white families, standing around the flip book in a parlor and probably believing themselves to be very sophisticated.

Both devices rely heavily on the retinal afterimage. The flipbook relies on the afterimage and persistence of vision because one’s vision has to recall what it saw in the immediate past to benefit from the flipbook’s progression of pictures. The kaleidoscope relies on these concepts because the fascination of the kaleidoscope is produced by the constant contrast between patterns. Binocular disparity is also evident in both devices, but in different ways. In the flipbooks, each eye is focusing on a different part of the picture while when one uses a kaleidoscope, they can only use one eye at once but will still see different images out of each eye. I find the phenomenon of binocular disparity to be quite interesting and am curious if it is being used in other fields, such as medicine.