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					                                              Photography
                                                        camera body focus mode switch is set to AF (auto
Introduction                                            focus) and the auto focus/manual switch on the lens
                                                        is set to M/A (manual/auto).
Photography involves producing a two-dimensional
image that is a reproduction of a three-dimensional     To manually focus, be sure the camera body focus
scene. Although the field of photography is much        mode switch is set to M (manual), then turn the
too complex to cover in a single experiment, this       manual focus collar (the inner collar on the lens)
experiment will highlight some essential elements       until the subject is in focus. Notice that as you
of digital photography.                                 rotate the manual focus collar, the focus distance
                                                        reads out in a display near the collar (in both meters
In this experiment we will be using a digital SLR       and feet). To focus at a particular distance, rotate
camera. The "SLR" stands for "single lens reflex".      the collar until that distance is indicated in the
A CD with an e-book about this particular camera is     display.
available in lab. Open the e-book to the section
entitled “Meet the Camera System.” Familiarize          Exposure Modes
yourself with the following parts and controls on
the camera; then keep the e-book handy for              The exposure mode dial allows for many different
reference.                                              settings regarding the exposure of the image. One
                                                        choice is Auto, in which the camera automatically
     On/off Switch              Shutter Release         chooses the exposure settings to get normal
                                                        exposure. This is often used if there is nothing
 Exposure Mode Dial          Manual Focus Collar
                                                        unusual about the photo you are taking, as it allows
 Camera Body Focus           Auto Focus/Manual          you to take pictures in different situations without
   Mode Switch                Switch (on lens)          stopping to figure out the best settings. However,
                                                        as we are doing an experiment, we want to be in
    Color Monitor                  USB Port             control of the parameters, so we will use A
 Main Command Dial            Subcommand Dial           (aperture mode) and S (shutter speed mode)
     EV +/- Select               Delete Button          settings.    Also useful are the various pre-
                                                        programmed settings such as portrait mode, as well
   LCD Data Panel               Review Button           as P mode, which allows you to program another
      Viewfinder             Multiselector Switch       setting, and M mode, in which you manually set all
                                                        settings.
Three important components of the camera are:
(1) a lens system to focus the light and form a sharp   F-number and A-Mode
image; (2) a variable aperture (opening) to control
the amount of light passing through the lens; (3) a     In A-mode you can manually set the aperture or size
shutter to control the amount of time that the          of the opening through which light passes into the
aperture is open and light can pass through.            camera. This changes the f-number of the aperture.
                                                        The f-number is defined as the ratio of the focal
                                                        length of the lens to the diameter of the iris
Focus
                                                        diaphragm opening. Since the focal length of the
Focusing of the image can be done manually or           lens commonly remains fixed, increasing the size of
automatically. Unless a particular focus distance is    the lens opening causes a decrease of the f-number.
called for, you can allow the camera to auto focus.     The f-number (sometimes called the f-stop) appears
To use the camera in auto focus mode, be sure the       in the upper right corner of the Data Panel (if it is

                                     PHOTOGRAPY                                                             1
not in view, press the +/- button). Each doubling of      larger the f-number, the wider the depth of field,
the f-number decreases the light entering the camera      and the greater range of distances are in focus.
by a factor of four, since the area through which the
light passes increases with the square of the             To get a great depth of field, however, requires a
diameter.                                                 small aperture, which in turn usually requires a
                                                          slower shutter speed. When the shutter is open for
If the f-number is increased, the light intensity is      a longer time, subjects have a greater likelihood of
decreased; thus the exposure time must be increased       moving, and that movement can blur a picture.
to maintain the same level of exposure in the photo.      Serious photographers consider both the depth of
In A-mode, the camera adjusts the exposure time           field they need and the possibility of subject
(or shutter speed) automatically as you adjust the        movement before deciding on their choice of
aperture.                                                 aperture and shutter speed.

                                                          Procedure
Shutter Speed and S- Mode
                                                          Throughout this experiment, be sure to record the
In S-mode, you control the shutter speed, and             aperture setting (f-number) and shutter speed used
therefore the length of time the aperture is open.        for each picture. If you forget to record as you take
Increasing the time would increase the level of           the picture, you can find the information in review
exposure of the photograph, if the f-number weren’t       mode. To enter review mode, press the review
increased to compensate. In S-mode, the camera            button. Now pressing the right arrow scrolls you
adjusts the aperture automatically as you adjust the      through photo information.
exposure time.
                                                          If a picture is taken which will not be used in the
The shutter speed appears in the upper left corner of     analysis, record the settings, record the reasons it
the Data Panel. The symbol ″ next to the number in        won’t be used, and delete it from camera memory.
the shutter speed means seconds, so 2″ means the
shutter is open for two seconds. However, if the          If your pictures are turning out too dark to analyze
symbol does not appear in the shutter speed, that         well, you can increase the exposure by holding
means it is a fraction of a second. For example 60        down the +/- button and rotating the main command
means the shutter is open for 1/60th of a second.         dial. Select a small positive numbers to increase
                                                          exposure slightly. Be sure that all photos taken in a
Under some light conditions, it may be impossible         single part of this experiment are taken with the
for the camera to get the exposure desired with the       same exposure setting.
aperture or shutter speed setting you have chosen.
In this case, the camera displays “LO” or “HI” in         Part I — Shutter Speed and Camera Movement
place of the shutter speed or aperture readout,
indicating that the exposure will be too low (dark)       In this part of the experiment, you will study the
or too high (bright). You should try to avoid taking      effect of camera movement on the ability to resolve
pictures under these circumstances, if possible.          fine detail in a photograph. Set up the camera on
                                                          the tripod approximately 4.5 feet from the Edmund
F-number/Shutter Speed Tradeoff                           Resolving Power Chart on the wall. This chart is
                                                          designed to test camera lenses. It has a large
"Depth of field" is the range of distances in the field   number of patterns with varying line frequency.
of view in which the objects are in sharp focus. For      The camera should be at such a distance that when
example, under some circumstances objects 10 feet         the chart is viewed through the viewfinder it fills
from the camera can be in sharp focus while those 3       the viewing area. The image should be in sharp
feet from the camera are blurred. In general, the         focus. Using S-mode, set the shutter speed at 1/30th

2                                     PHOTOGRAPY
of a second. Click the shutter to make the exposure.     Compare the two images taken with a speed of
Remove the camera from the tripod and hold it in         1/30th of a second. In which of the two images of
your hand at approximately the same distance from        the chart are the finest lines resolved — the one on
the chart. Using the same aperture setting and           the tripod or the one made by holding the camera in
shutter speed, carefully take another picture of the     your hand? Why does the resolution depend on
chart. This second exposure will measure how             whether or not you use a tripod?
steady you were able to hold the camera.
                                                         Now compare the three images made while holding
Take four more pictures of the chart, holding the        the camera in your hand. Which has the best
camera in your hand — two with faster shutter            resolution? Which has the worst? Explain why this
speeds and two with slower speeds.                       is the case.

Part II — Shutter Speed and Subject Movement             Part II

In this part of the experiment, you will study the       Examine the images of the moving subject. Are the
effect of subject movement on the clarity of a           subjects blurred in any of the images? Which
photograph. Take five pictures of a moving subject.      shutter speeds gave the least blurring? Why? Was
Use the tripod for all five pictures, and use the same   it difficult to get a fully exposed image without
speed settings used in part I.                           blurring? Under what circumstances might it be
                                                         impossible to get good exposure without blurring?
Part III — Aperture and Depth of Field
                                                         Part III
In the third part of the experiment, you will
determine the depth of field for different aperture      Examine the images of the series of numbers.
settings. For this part of the experiment it will be     Which numbers are in focus in each image? Why
necessary to position the camera to take a picture of    are some numbers in focus while others are not?
the series of numbers placed at varying distances        Which aperture value(s) gave the best depth of
from the camera, ranging from 25 cm to 8 m. The          field? Which gave the least depth of field? Does
camera should be mounted on the tripod. Focus the        this agree with expectations?
camera at 1 m. Take a series of four pictures using
A-mode. Vary the aperture from one photo to the          The light entering the camera is proportional to the
next, with at least a factor of four between the         exposure time and inversely proportional to the f-
lowest and highest f-numbers. The camera will            number squared, if the ambient lighting doesn’t
automatically set the shutter speed, but try to avoid    change. Divide the exposure time by the f-number
speeds slower than 1/15th of a second or faster than     squared for each of the three images. Is the value
1/500th of a second.                                     approximately the same for all? Why or why not?

Upload all useful pictures to the computer using the
USB cable, and analyze them for your report.

Analysis

Part I

Examine the images of the Edmund Resolving
Power Chart, zooming in as needed. Look for the
finest lines (greatest line frequency) in which the
three lines in the group are distinguishable.

                                      PHOTOGRAPY                                                           3

				
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