What I want to show to the alien is photography.
In the middle of the picture, there are two persons taking pictures. One is posing, and the other is back to us, holding a camera toward the posing person. We can see the screen of the camera in front of us. And there is a dotted arrow from the screen to an enlarged view of the camera screen showing a picture of the posing person which is as same as him.
An arrow from the camera held by the person to a camera’s profile map so that can let aliens understand what we want to show to them and what a camera is. And there are another three arrows from the camera’s profile map separately to tree main elements of a camera. The first is a viewfinder. A ray of light shots from outside into the viewfinder and reflected by a retroreflector in the viewfinder’s profile map then to an eye. Another ray of light shots from the outside into the viewfinder then to a photosensitive element in the viewfinder. The retroreflector and the photosensitive element are drawn as long and thin rectangles. The rays of light are drawn as dotted arrows. The second is a pentaprism, which is used to reflecting the inverted image which through a focusing screen to the viewfinder. Cause it is a transparent element, we can show it in grey, and different face can use different level of grey. The third is a shutter. A shutter is mainly composed of a gear and transparent baffle. When you press the button, the gear will push the baffle between the lens of the camera and the photosensitive element to open and close quickly. To show this process, we draw two images showing the open and close of the shutter. At this point, we have finished the introduction to the camera.
Then we are going to introduce the theory of taking a picture. The theory is called image by ping hole. There is a person standing in front of the camera, and two rays of lights separately come from the head and feet of the person then focus on the lens of the camera, projected onto the photosensitive element. What’s more, the image on the photosensitive element is inverted.
In the lower part of the whole picture, we are going to introduce the genre of photograph. From left to right is the landscape picture, still life picture, portrait picture and abstract picture. We use a mountain and river picture to show the landscape picture, and fruit like apple, pear and orange to show the still life picture, and an alien’s image to show the portrait picture, and a distorted alien’s image to show the abstracted picture. The reason why we use alien’s image instead of human’s is to make them better understand the genre of photographs.
Last but not least, the reason why we want to introduce photography rather than movies is that movies have time notion so that when aliens watching movies, they can know the ending at the beginning of the movies.