Expository text - How does instant photography work?

When I was a kid, my parents used to have a polaroid camera. They took pictures and shortly afterwards the image magically appeared. For those of you who, very much like me, have always wondered how this was even possible, here is the explanation.

Instant film or film for polaroid cameras is very similar to regular film. The main difference between the two of them is the developing process. While a regular film has to be developed externally, in a dark room, the instant film already has all the needed chemicals in its layers. Therefore, the picture develops as soon as it's been taken.

The film itself comprises of several different layers, as you can see in the image.

When a photograph is taken, the silver atoms on the film react with the light photons and create an image. In order to get a real picture, it needs to be developed. For this, rollers inside the instant camera spread the reagent layer, which is made of opacifiers (light-blockers), alkali (acid neutralizers), white pigment and other elements.

Underneath the reagent layer, there are three different light sensitive layers (blue, green and red). Under each of them lies a dye developer in its complementary color (yellow, magenta and cyan respectively). When a certain color of light reaches its sensitive layer, the opacifiers block the dye developer right underneath it. The other two developers can move up to the image layer.

This means that if blue light hits the blue sensitive layer, the yellow dye developer gets blocked. Therefore, only magenta and cyan reach the image layer, creating the color blue.

If you have ever seen an instant photograph develop, you know that it is usually greyish at first and only slowly becomes visible. This is due to the opacifiers. The reagent chemicals not only work their way down through the dye developers but also up through the image, timing and acid layer. The picture will stay greyish until the opacifiers and the alkali reach the acid layer where they react. This reaction makes the opacifiers become invisible and the picture visible. The timing layer slows the reagent chemicals down, leaving the picture underneath enough time to develop.

And voila, that is how instant films work. You see, it, unfortunately, has nothing to do with magic after all. 

Camera Lucida - How helpful were the instructions?

Tim Hunkin’s instructions on how to make a camera lucida appear to be easy to follow due to the pictures and the text accompanying them. However, the set of instructions turns out to be rather confusing when examined more closely. Firstly, the instructions given are incomplete. For example, the instructions mention a hole to look through although said hole was never mentioned before. Similarly, the installation of the reflecting plastic plate is missing. The author probably left these steps out purposely as they seemed obvious to him. To someone who has never  built a camera lucida before, however, these steps are essential. It would also have been more helpful to number the steps, even if the text is very short. Another confusing aspect that the reader constantly has to jump between the text and the pictures. Neither text nor pictures are sufficient on their own to explain how the camera is built without causing utter confusion. Overall, the text itself is not badly written. It is concise and understandable, but the fact that it is only partially complete makes the instructions rather difficult to follow.

Napalm Girl Descriptive: Group 2

This black and white picture was taken during a napalm attack during the Vietnam War in 1972. The landscape is bare save for an overgrown field and a few buildings in the background. In the centre of the picture is a young naked girl, a haunting scream on her face as she runs down a cracked asphalt street from the enormous cloud of smoke behind her. She is surrounded by five clothed children and four armed and uniformed soldiers. The children wear terrified expressions on their faces, whereas the soldiers do not look particularly frightened to the naked eye. The malicious dark colour of the cloud, when compared to the light gray of the street leading the
innocent children into safety from the ever closer growing danger, makes the situation look even more bleak.The picture is devoid of colour but full of life nonetheless. The children’s screams resonate in the viewer’s ears, as does the rumble of the ongoing air raid and humanity’s inherent fear of their own demise is reflected in the children’s faces. The poisonous cloud seems to have a life of its own as it appears to close in on its terrified victims, rendering the viewers unable to tear their eyes away from the scene in fear that the break in eye contact will set the scene into motion.