Three sentences summarizing the document: A photogram is a photographic image made without a camera by placing objects directly onto light-sensitive material like photographic paper and exposing it to light, resulting in a negative shadow image of varying tones depending on the transparency of the objects. Camera controls like exposure duration, aperture size, and focal length are interrelated and impact the total light reaching the film, and many cameras can automatically adjust some or all of these controls. The f-number system standardized the effective aperture sizes of lenses, with smaller f-numbers indicating larger apertures.

1. PHOTOGRAMS

2. PHOTOGRAM A photogram is a photographic image made without a cameraby placing objects directly onto the surface of a photo-sensitive material such as photographic paper and then exposing it to light. The result is a negative shadow image varying in tone, depending on the transparency of the objects used. Areas of the paper that have received no light appear white; those exposed through transparent or semi-transparent objects appear grey. Light exposed paper

3. EXOPSURE AND RENDERING Camera controls are inter-related. The total amount of light reaching the film plane (the 'exposure') changes with the duration of exposure, aperture of the lens, and on the effective focal length of the lens (which in variable focal length lenses, can force a change in aperture as the lens is zoomed). Changing any of these controls can alter the exposure. Many cameras may be set to adjust most or all of these controls automatically. This automatic functionality is useful for occasional photographers in many situations. The smaller the f/number, the larger the effective aperture. The present system of f/numbers to give the effective aperture of a lens was standardized by an international convention. There were earlier, different series of numbers in older cameras. Photogram Exposure Photogram Rending