Not at all. It is true that we do not see things upside down, but this is because of mental readjustment during the passage of the impressions from the eye to the brain. Now let us suppose that we have our camera loaded with film, and that mother has succeeded in keeping the baby quiet long enough for us to uncover the lens for an instant and let the points of light through to the film. The next question is, how are we going to make the resulting image permanent. We know that it is there, but in its present state it is not going to do us a great deal of good. In fact, if we should peek in the back of the camera, and to do so would ruin the exposure, we could not even see it. But let us go back a bit. We ought to know a little something about the composition of this film on which the image has been projected. In brief, film is a cellulose base coated with silver bromide and gelatine. If we were using a plate the only difference would be that instead of cellulose as a base we would have a sheet of glass. The gelatine is there to afford lodgment to this sensitized silver. The silver, being sensitive to the action of light, is there to record the image. As soon as one of these silver particles has been touched by light, it becomes imbued with the power of holding whatever the lens has transmitted to it. The image was formed, we remember, by points of light grouped in the same relative positions as the points of light of the object we were photographing. Consequently it is only those silver particles within the image-forming area that are affected, because that is where the light struck. The lens, then, gathered in the points of light and dispersed them on the film so as to form an image. The silver particles held this image, but not visibly--it is a latent image, and it is the purpose of development to bring it out. It is the particular business of a chemical called “pyro” to release this latent image. When attacked by pyro, those silver bromide particles which have been affected by light--and only those--change to black metallic silver. After all the silver bromide particles, the ones that held the image, have been transformed into metallic silver, another chemical called “hypo” effectively disposes of all the silver bromide that was not affected by light. Now only the image-forming silver bromide particles remain, and these have been transformed to metallic silver. The result is a permanent image--a negative. But it _is_ a negative, so called because everything in it is reversed--not only from left to right, but in the details of the image. Mother’s dark blue gown looks light, for example, and baby’s white dress, dark.