In the good old days, people like Leonardo da Vinci would simply put a piece of paper where an image was formed and start drawing. The mediocre results that he achieved aren't likely to satisfy a serious-minded visual artist today. So perhaps it is time to think about putting some film behind the lens to record the image. Sadly, however, I was a math major in college and got class low on the first exam in freshman chemistry. Slide film is magic stuff that starts out opaque and turns transparent as more light hits it.
Negative film is magic stuff that starts out transparent and turns opaque as more light hits it.
The opacity of the film is increasing on the y-axis. If you look at the right of the graph, you'll notice that the film doesn't ever become perfectly clear. Only over a small range of light intensity does this film react differently to different amounts of light. Right now, let's think how this information is presented to consumers. If you go to the camera shop, the Agfa Scala box does not have a curve on it like the above.