Page 54 - CEREC Q2 | 2014

52 | CERECDOCTORS.COM | QUARTER 2 | 2014
sensor. A large F-stop number means
that the opening of the lens of the
camera is small. The larger the F-stop,
the less light allowed in. Conversely, the
less light that goes in, the longer your
shutter needs to be open to allow for
proper exposure.
A small F-stop, by contrast, means that
the lens is wide open. The wider the lens,
the less time a shutter needs to stay open
to ensure the same exposure (Fig. 6).
The smaller the F-stop (which means
the larger the lens opening), usually
the smaller the depth-of-field. If we
look at two photographs — one taken
with a small F-stop number, and the
other with a large F-stop number — you
will see that the photos with the large
F-stop will have a deeper depth-of-
field, meaning that the entire photo-
graph is in focus. When we have a small
F-stop number, and hence a shallow
depth of field, the items in the back
of the photograph will be out of focus
(Figs. 7-8). For dental photographs, we
want the F-stop to be large, meaning
small opening on the lens. This smaller
opening also means that the picture
will be in focus both in the front and in
the back.
The shutter speed refers to how
long the shutter stays open to expose
the photograph properly. The shutter
speed is indicated by a number; these
numbers run, typically, 60-200 and
refer to a length of time. For example,
125 refers to 1/125th of a second that
the shutter is open. And 60 refers to
1/60th of a second that the shutter is
open. The higher the number, the less
time the shutter is open.
For dental photographs, with our 100
mm macro lens, our normal settings
are typically an F-stop of about 29
with a shutter speed of 125. On your
camera, you can set these numbers in
the manual setting. This will result in a
properly exposed photograph for intra-
oral photos.
Fig. 7: With the F-stop setting set to a
low number (a large opening of the
lens), there is a shallow depth of field.
Everything in front of and behind the
subject is out of focus
Fig. 8: Increasing the F-stop number
(a smaller opening of the lens) allows
everything in the photo to be in
proper focus
Fig. 9: An example of an under exposed
photograph. The shutter speed in
this case was set too high (meaning a
shorter time that the shutter is open).
Fig. 10: By lowering the shutter speed
number, the shutter stays open longer
resulting in a properly exposed
photograph.
Fig. 11: Proper settings and equipment
result in a properly exposed
photograph that allows the right
communication between clinician
and patient.
| | | P U R I
7 8
If you want to adjust the exposure
(make the photo brighter or lighter)
you would adjust your shutter speed.
To darken the photo increase the
shutter number; to lighten the photo,
decrease the number (Figs. 9-10).
Proper photography requires proper
equipment. Cosmetic dentists using
inexpensive point-and-shoot cameras
don’t do their clients justice. By having
quality photographs, the clinician not
only can have better communication
but also better be able to critique their
own work. A good photograph is crit-
ical to the practice of a cosmetic dental
practice (Fig. 11).
For questions and more information,
Dr. Puri can be reached at
sameer@cerecdoctors.com.
9 10
11