August 2003 S M T W T F S           1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30  July 2003 S M T W T F S     1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31     Daily Logs This material is based upon work supported by the National Science Foundation under Grant No. 0230236. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Please select a name below to see the individual log. Bob McCarthy | Gerhard Behrens | Andreas Münchow Log - July-31-2003 by Robert McCarthy Previous | Next Cameras Robert McCarthy Last night Lee Narraway gave a talk on photography. I mentioned yesterday how Lee learned the “art” of photography by experimentation. Well, she also knows the “science” of photography too. Her talk was mostly about how to take better pictures by critiquing digital photos that people onboard sent to her. I think EVERYBODY in attendance learned something from her comments. That’s another benefit of being a teacher, always learning new things. The same holds true for a lot of other professions, but teachers must be role models of life-long learners. The major question high school teachers hear is, “why do we need to know this?” And quite frankly, most of my students don’t need to know all the formulas and “laws” I teach them. But understanding how things work and being able to ask new questions is a skill I’m also teaching. Teaching them problem solving skills employers are looking for and they will use for the rest of their lives is equally as important as the physics. (But really, who doesn’t love physics?) So today, I want to give a brief explanation of how a camera takes a picture. The lens is convex (converging), so the light coming in from the object is bent through the focus point of the lens. Between the lens and the focal point of the lens is the aperture. This is a variable opening that limits the light reaching the shutter. The shutter is past the focal point but before the film. Through the lens viewing cameras have a diagonal mirror on the shutter. This way, you look in the viewfinder and with the use of two diagonal mirrors, you essentially see your object the way the film will “see-it”. When you click the shutter release, the mirror flips up out of the way and the light exposes the film. Notice that the image is upside down and much smaller on the film. It is upside-down because the rays cross over at the focal point of the lens. When you focus on the object, you are changing the distance from the focal point of the lens to the film. This is accomplished by moving the camera lens slightly. The farther away your object is located, the closer the lens needs to be to the film. For an “infinite” object, the film is at the focal point of the lens, and the camera is as compact as it can be. For an object close to you, you need to extend the lens out away from the camera body, because the image distance (the distance from the lens to the film) must increase. Different lenses have different focal lengths. The greater the focal length, the more the object is “zoomed-in”. The greater the aperture opening (designated by f-stops), the more light gets in to expose the film. Thus you need a fast shutter speed, so not to overexpose the film. An f-stop of 2.8 is a large opening. This is good for fast action shots, where you want to freeze the motion. Conversely, an f-stop of 22 is a very small aperture opening. This is nice if you want the greatest depth of field in focus. Lastly, disposable cameras have a fixed focal length and a fixed aperture size (usually about f-11) to allow a large depth of field, minimizing the need to focus. Now all we need is subject matter. I think we’ll be looking for walruses when the “clam-team” starts their research, but that’s another day and another story. I’ve included some spectacular digital photographs, mostly from Scott McAulliffe.