The Exposure Triangle – Aperture, Shutter Speed and ISO


There's more info on this topic at The exposure triangle explains how the individual aspects of exposure, i.e aperture, shutter speed and ISO, affect the final exposure of the photo. It's a useful way of describing the relationship between the three aspects of exposure. Each side of the triangle represents one of the three variables, aperture, shutter speed and ISO. Adjusting just one of these will will change the appearance of the photo based on your settings. It's important to understand that unless you are in the Manual Exposure Mode, changing any of the three settings will not make the image darker or lighter. That's because in any of the semi auto modes (such as A/AV, S/TV, or P), the camera will automatically compensate by changing one of the other settings. Aperture The aperture, which is part of the lens not the camera, controls the quantity of light entering your camera. Just like the pupil of the eye, the larger the aperture, the more light is let in. The aperture is set using what is known as F numbers, i.e f2.8, f4, f5.6, f8 and so on, and the smaller the number, the larger the aperture (only a small elite of quantum physicists know why this numbering system is so perverse!!). These numbers are sometimes referred to as a 'stop', and each stop allows in twice as much light as the previous one, so or example f4 lets in twice as much light as f5.6 Shutter speed The shutter speed, measured in fractions of a second, controls the duration of the exposure. Just like window shutters, the longer the shutter is held open, the more light is let [...]

The Exposure Triangle – Aperture, Shutter Speed and ISO2020-06-11T18:48:49+01:00

Aperture vs Shutter Priority Mode – Which should you use?


As well as the fully automatic green Auto mode, all DSLR's have several other very useful exposure modes. Aperture Priority and Shutter Priority Modes are two of the most popular semi-automatic modes. But what many people don't realise is that generally speaking, these two modes will give you exactly same exposures. For example, take a look at these settings which show equivalent settings (assume that the current light level is giving a reading of aperture f4, shutter speed 1/250th of a sec):- Every one of the above settings will give you the same exposure, for example, compare f5.6 at 1/125th of a second with f11 at 1/30th of second. f11 is 2 stops smaller than f5.6 (so less light is let in), and so to compensate for that, the camera chooses 1/30th of a second, which is 2 stops slower than 1/125th (shutter is held open longer). Also, the only difference between aperture priority and shutter speed priority, and the clue is in the name, is which setting you have direct control over, either the aperture or the shutter speed. Aperture or Shutter speed priority So that leaves a burning question. If it makes no difference to the exposure, why then choose aperture priority over shutter speed priority or vice versa? Well, it all comes down to the creativity element of photography. As well as controlling exposure, the aperture is used to control depth of field, that is, how much of the image is in focus from front to back, and the shutter speed is used to control motion, so whether you want to freeze the action or show movement. With that in mind, for landscapes you would generally use aperture priority and choose [...]

Aperture vs Shutter Priority Mode – Which should you use?2018-01-22T19:46:01+00:00
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