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12. How do Aperture, Shutter Speed, and Sensitivity play together? Now we realize that the exposure quality and the artistic value of our shots are impacted by both the Aperture and the Shutter Speed settings because both of these mechanisms effect how much light is allowed through to the film or sensor. The following scenario is intended to help us solidify our understanding of the two concepts and their interaction with each other. Photographing a water fountain - We start our manual adjustments by using our spot meter on the neutral grey concrete. This gives us a baseline for our exposure. - Envisioning the scene, we decide that we’d like to have the background out of focus while the turtles remains in crisp focus. To do so, we’ll adjust our aperture to a larger setting (meaning a smaller f-stop), lets say F/5.0. This reduces our Depth of Field to blur the background. However, because we are now letting more light pass through by opening up our aperture, our exposure has changed. In order to adjust our exposure back to its original neutral value, we’ll need to adjust something. We don’t want to decrease our aperture because it will comprise the artist effect rendered by our reduced depth of field. So we will adjust our shutter speed. We reduce our shutter speed to a smaller interval to compensate for the additional light flowing through the camera. We’ve preserved our depth of field and our exposure! We also notice the convenient effect that the small shutter speed only captured the action occurring in that small period, so the turtles and the near-by ripples on the water seem frozen in time! The water fountain would seem frozen as well, but it is far enough into the background that is being blurred due to the narrow depth of field.
ISO 100, 59mm, F/5.0, 1/800 sec
- But after looking at this picture, we wonder how it would look if the waterfall was streaming rather than frozen. To accomplish this, we set our shutter speed to some longer interval. Let’s say 1/30th of a second. This means that the shutter will stay open long enough to record 1/30th of a second’s worth of action on the film or sensor. We have to be careful here though. We want a long enough shutter to capture movement in the water fountain, but not long enough to chance the turtles moving in the foreground. The side effect of this setting is that it also lets much more light in from the entire scene than before. So to return our exposure to its original setting, while still preserving our desired artistic effect, we’ll need to compensate for the abundance of light by making our aperture smaller (a higher f-stop value). The larger aperture setting also increases our depth of field, so we'll notice that the background is in much clearer focus now.
ISO 100, 59mm, F/32, 1/30 sec
From this example it becomes clearer, the Aperture and the Shutter Speed work in tandem. As if on a hanging balance, if one is adjusted, the exposure will shift, and the other must be adjusted in the opposite direction to rebalance again. The photographer must be conscience of this relationship in order to properly expose while implementing some artistry in the shot. The example above does not necessitate any increase in sensitivity because the scene is adequately lit for IS0 100 settings. However, if the scene were at dusk, the photographer may find that the available light is not adequate to render the results desired. For instance, the short shutter speed necessary for freezing the water fountain may not yield enough light to adequately expose the scene, even with the aperture as large as possible. In this instance, one could adjust the sensitivity of the photo-sensitive medium to reset the tolerance for the shot. After which, the aperture and shutter speed could be adjusted within the new, brighter tolerance. As stated in the section on sensitive above, a word of caution should be extended about the possibly for noise introduced at higher sensitivities. <<PREV 1 2 3 4 5 6 7 8 9 10 11 12 13 NEXT>>
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