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By: BriarCraft , 10:52 PM GMT on January 14, 2014
My point-and-shoot camera died in 2011 and I bought a Fujifilm Finepix HS20EXR "bridge" camera. Out of the box and on "Auto" I was thrilled with the marked improvement in photo quality. It didn't take long, though, for me to get curious about all the buttons and menus, so I started reading the 132-page manual. And got really confused at all the terminology and jargon.
It took me a couple of years, but I finally decided I had to learn more in order to understand the manual and, in turn, the camera. Why have all these fancy controls if I had no clue how or why to use half of them? The answer to my questions was found in a textbook, "Complete Digital Photography, 7th edition" by Ben Long. With 600 pages and supplemental material available online, this book is designed to be helpful to any photographer with any digital camera.
I highly recommend this book to anyone who isn't already an expert photographer. The rest of this blog entry is about the elements of exposure that had me confused, baffled, and frustrated. The illustrations used are scanned images from the book and I hope it will inspire some of you to buy the book to learn more.
My biggest question, starting out, was "Why doesn't the camera capture the same thing I see?" and that was just where the book started. One of the key points I learned was that the eye and the camera simply have different capabilities.
For photographers, every time the amount of light in a scene doubles, the scene is brightened by one stop or f-stop. And if the light in the scene is cut in half, it is darkened by one f-stop. Dynamic range is the difference between the darkest and lightest tones that can be perceived. The entire dynamic range of the human eye is about 30 stops, but when looking at a single scene the eye can discern a dynamic range of only about 15 stops. By comparison, a digitial camera has a total dynamic range of 10-12 f-stops and in any particular scene, you can expect to capture a range of about 5-9 stops. And that is why a camera today simply cannot reproduce exactly what you see.
Because the camera perceives a narrower dynamic range of light than your eye, a decision must be made as to which portion of the full dynamic range the camera captures. In most cases, the camera's "Auto" setting does a fine job of deciding what to capture in a scene. Other times, you might want to capture the scene in a particular way. Since you can't capture the entire dynamic range, you might want to pick a range that conveys what you "felt" when looking at the scene.
Choosing a smaller aperture will keep more light from getting to the camera's image sensor, but the aperture setting has another effect on the image. As you go to a smaller aperture, the depth of field in your image gets deeper, bringing more of the scene into focus.
A camera's shutter is a little door that opens and closes to control how much light passes through the lens to the image sensor. Shutter speed is a measure, in seconds, of how long the shutter stays open. A faster shutter speed exposes the sensor to less light. You'll most often see shutter speeds listed in fractions of a second, as in 1/60th, 1/125th, etc., but cameras also have settings for longer durations, such as 1.5 seconds and 30 seconds. Shutter speed affects more than the amount of light. Shutter speed also affects the "perception" of motion.
Since both shutter speed and aperture affect the amount of light, it is important that when you adjust one parameter, you need to adjust the other in the opposite direction to avoid over- or under-exposure.
Then, there is ISO, the third exposure parameter just to make it all more confusing to the beginner. ISO is a standard for measuring the sensitivity of film. (ISO stands for International Standards Organization.) Digital camera makers adopted this standard early on as a way of specifying the sensitivity of an image sensor. When you increase the ISO setting on your camera, you are adjusting the sensor to become more light sensitive. As the image sensor becomes more sensitive, it will require less exposure to be able to "see" a scene. This allows you to shoot in very low light levels because ISO, shutter speed, and aperture all share a reciprocal relationship.
The downside of a high ISO setting is digital "noise", which comes in two flavors: luminance noise and chrominance noise. Luminance noise is bright speckles that appear in your image, usually in the shadow tones. Chrominance (color) noise appears as splotchy patterns of color, also usually in the shadow tones, most commonly red or magenta splotches. Luminance noise closely resembles film grain or texture, while chrominance noise looks very "digital" and is extremely difficult to remove with editing software.
In summary, balance is the key. Depending on what part of a scene you want to emphasize or draw attention to, you have three parameters to juggle. It takes awhile to get used to this and perhaps the best way is to practice. Pick a subject or scene and take several shots using different aperture, shutter, and ISO settings. Then look at the result on your computer, not the little LCD screen of your camera.
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Updated: 5:44 AM PDT on October 13, 2015