Lesson Six: The Sharpness Triad, Part II

Last time we talked about aperture which is the first part of the sharpness triad.  If you've tried to open your aperture to its widest setting and still can't get the picture sharp, the next thing you can try is to adjust the shutter speed.  Here's the way the relationship between aperture and shutter speed works.  The bigger the aperture, the less the amount of time the shutter should have to remain open to let enough light in to get a sharp picture.  Here's a little experiment you can try at home.  Set your camera mode to shutter priority (Tv mode).  Now set the shutter speed to it's fastest setting which should be 1/x second where x is a number.  You want x to be the largest number on your camera.  Go ahead and take a picture.  Now change the shutter speed to the second fastest setting.  Take the same picture.  Now keep doing this, decreasing the shutter speed.  You should notice that as the shutter remains open longer, the picture will get brighter up to a certain point where you'll start noticing blurry pictures (usually when the camera is hand-held and the shutter speed is set to a couple of seconds or more).  What's happening here is the camera is taking the picture even though there is not enough light (leading to the dark pictures).  You've told the camera (by selecting Tv mode) that I don't care that there's not enough light.  Just take the picture and close the shutter after x seconds has passed.  As the shutter remains open longer, you are letting more and more light in (accounting for the picture getting brighter) until you get to a point where you can no longer hold the camera perfectly still for the full duration that the shutter remains open (leading to the blurry image).