We still must use those to make a “correct” exposure, but we can also better consider the creative implications of our choices. Now making an exposure truly becomes a “three-ball juggling act.” We can change Aperture, Shutter Speed, or ISO with each shot if we like. In the digital world, ISO can be changed whenever we like, even from shot to shot. It had less grain than did an ASA 400 roll, but it was also less light sensitive. Put in a roll of ASA 64 film and that was what you lived with for the whole roll. In the film days, film sensitivity was fixed. ISO measures how sensitive we make the sensor in a digital camera. Like an audio amplifier, lower settings keep the background “noise” less while higher settings which amplify the signal also introduce more noise and distortion. Of the three components of the triangle, ISO choice has implications, but probably less so than the others. Short (faster) shutter speeds will help us freeze motion by capturing a “thinner slice of time.” Longer (slower) shutter speeds can allow us to “stretch time” and cause moving objects to blur. You might think of the shutter speed as the “slice of time” we expose the light-sensitive medium to light. A shutter speed of 1/2 second is a longer time the shutter remains open than 1/250th of a second. Remember, shutter speed is represented in whole or fractions of as second. The shutter speed you choose also offers creative possibilities. In a landscape photo where we want front-to-back sharpness, a small aperture may be better. In a portrait, we might want an unfocused, simplified background with a limited depth-of-field, so a large aperture would be a good choice. Therefore, the bigger f/numbers like f/22 represent smaller apertures (holes), while the small f/numbers like f/2.8 or f/4 represent the larger apertures.Ĭreatively, we can use smaller f/stops to increase depth-of-field and larger ones to limit it. At those extremes there is no detail to recover it is either totally black and “blocked up,” or totally white and “blown out.” In theory, an image which stays “between the goalposts” such that none of the tones go off either edge is a “correct exposure.” In editing, we can redistribute the tones so long as they have not gone to “0” which is total black, or 255 which is total white. At the far right are the highlights, on the far left, the shadows. The first consideration is technical, the second creative.Ī histogram shows us the 256 shades of gray for a given image. How can we use the three components of the triangle most creatively?.What is the correct amount of light to let into the “box” rendering all tones in the subject and capturing everything from the blackest shadows to the brightest highlights, and.There are two basic things to consider when making an exposure: From the simplest to the most complex camera, three things – Aperture, Shutter Speed, and ISO are the factors affecting Exposure.
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