SECTION III

SECCTION III Exposure To take a picture you need to control exposure. Exposure refers to the amount of light going through the lens to the sensor to create the image. too much light = overexposed photo not enough light = underexposed photo Exposure depends on Available Light. Available Light - AL Three factors control the exposure of the sensor: 1.The ISO number 2.The shutter speed 3.The aperture of the lens Got to set them correctly to take a properly exposed picture (not too dark, not too bright). The light meter built into the camera reads the amount of AL and sets both values (shutter speed and aperture) to expose correctly, according with the ISO. 1. The ISO number It indicates how sensitive the sensor is. In the past ISO was named ASA or Film Speed. THE LARGER THE NUMBER THE MORE SENITIVE THE SENSOR ISO SCALE 100 200 400 800 1600 With a high ISO number you need less light to create your image. This is to be used in low lighting, but also when you need to stop action (sport photography). Increase ISO: - in low AL - to take action photos 2. The shutter speed THE SHUTTER SPEED CONTROLS THE LENGTH OF TIME OF THE EXPOSURE THE LARGER THE NUMBER THE LESS LIGHT GOES TO THE SENSOR 3. The aperture scale THE APERTURE CONTROLS THE INTENSITY OF THE LIGHT ONTO FILM THE LARGER THE NUMBER THE LESS LIGHT GOES TO THE SENSOR ALL THREE OF THESE EXPOSURE FACTORS ARE RECIPROCAL The Law of Reciprocity The law of reciprocity means that you can compensate a change of one exposure control with an opposite change in the other exposure control and still have the same total exposure onto the film. Shutter Speed Aperture 30 32 60 22 125 16 250 11 500 8 1000 5.6 These couples are all equal exposures for the film – the same total quantity of light goes to the sensor. The difference created by setting the different combinations of aperture and shutter is aesthetic! It depends on how you want the picture to look. If you want lots of sharpness you must choose a closed down aperture and have a slower shutter speed; if you want “stopped action” you must choose a fast shutter speed and a more opened aperture. NOTE: this is just an example; in different lighting conditions and with different ISO numbers the couples will be different too. Controlling Both Motion and Depth of Field Depth of field is an expression that means the zone of apparent image sharpness. While human eyes see everything in sharp focus, the camera sees in a selective way. Selective focusing means that only a portion of the entire picture will be sharp; the rest (in general both foreground and background) will be blurry. Depth of field is the distance including all sharp points. Depth of field can be increased rising the aperture number. To take a picture of a landscape, as we want everything to be sharp, we will set a big aperture number: 16 or 22. Conversely to take a portrait we will focus on the person face and we will use a small aperture number to have a blurry background. Setting both shutter and aperture you can control your image in terms of sharpness and motion. A high shutter speed number gives stopped action A low shutter speed number gives blurred motion A high aperture number gives great depth of field (sharpness) A small aperture number gives little depth of field (sharpness) But it is the given light in which you are shooting that determines the limits in which you can work. IMPORTANT SETTINGS: Read the user’s manual to learn how to operate your camera. Exposure: Shutter Speed + Aperture SUGGESTED VALUES shutter s. aperture 200 ISO in the sun 125 16 in the shade 60 11 In the evenings and indoor (depending on available light) 200 ISO 60 11 30 11 30 8 15 8 15 5.6 If you set shutter speed below 15 you will get camera shaking. Zooming All digital cameras have a zoom lens. This means you can zoom in and out. In other words you can change the Focal Length of the lens. This way you get more or less of the scene in front of the camera and you also make the subject smaller or bigger. Focal Length (millimeters) 28 mm 35 50 (standard for 35mm film and full size digital camera) 80 135 200 400 800 T = telephoto lens (high number, over 50) - to make the subject bigger W = wide angle lens (low number, below 50) - to get more of the scene Focusing: All digital cameras have automatic focusing. Professional cameras have both automatic and manual. If you get to close to the subject you can’t get it in sharp focus. The limit depends on the camera (usually it’s around 12 inches). If the subject you want to focus on is not in the center of the image point the camera to it, then press the button half the way and keep it down. Move the camera back to the right framing and shut. When using your 35mm film SLR camera, you have to get the subject in sharp focus manually.