endodontics
feature
INMicrophotography
FOCUSusing the
dental operative microscope
by Jorge Zapata, DDS
Fig. 1
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OCTOBER 2015 // dentaltown.com
Microphotography, as
it relates to dentistry,
is the art of capturing
pictures through the dental
operative microscope
(DOM). One of the main
differences between
microphotography and
macrophotography is
that no lens is attached
to the camera in
microphotography. This
creates unique challenges
for the clinician in capturing
quality images.
endodontics
feature
These challenges include: controlling
the vibration of both the microscope and
the camera, working in conjunction with
live view monitors, and understanding
the par-focal adjustment of the microscope to assure clear focus of both the
camera and microscope.
Avoiding vibration
In microphotography, many different
sources of vibration can affect the sharpness of pictures, and each must be isolated and eliminated in order to capture
the highest-quality images.
In Fig. 1, (pg. 38) dots and thin,
short, horizontal lines can be noted.
These distortions create the sensation that
the picture is moving sideways. This perceived motion is the result of one or more
of the following factors:
• Vibration in the body of the
microscope
• Tremor of the clinician’s hand while
holding the dental mirror
• Shaking of the patient’s jaw
• Vibration related to the movement
of the internal mirror of the camera
(SLRs) at moment of shutter release.
Some of the vibration can be
improved and controlled by the clinician.
However, some vibration will continue to
exist, despite the clinician’s best efforts to
overcome it.
Vibration of the scope’s body is nearly
impossible to eliminate. Other vibration
can be improved with the use of surgical
armrests, a mouth prop, a remote control
and a fast shutter speed of at least 1/125
and above.
Out of focus
The desire of every photographer is
that each picture captured will be clear,
and every detail in the given subject accurately reproduced; any tiny movement can
affect the final result of the image. The
photographer can correct for vibration,
but the camera may still capture images
that are not sharp because of focus issues.
So how can the photographer take
pictures that are sharp and full of the
desired detail? What specific techniques
do professional photographers use to capture acute images? Sometimes the photographer will find that when the focus is
set on the foreground of the subject, the
background goes out of focus, and vice
versa. The answer to this dilemma is to
use the depth of field (DOF) correctly.
Photographer Bryan Peterson defines this
in his book, Understanding Exposure, as
the area of sharpness (from near to far)
within a photograph.
The real key
to successful
microphotography
is to find the precise
balance between
the camera and the
microscope.
It is important to understand DOF
in microphotography in order to control
image sharpness. In microphotography,
the DOF is very shallow, so missing the
focus point by even a millimeter causes
the pictures to be out of focus. The DOF
is impacted by the level of magnification. For example, lower magnification
produces more DOF, as demonstrated in
Fig. 2. Whereas Fig. 3 shows that higher
magnification has a narrower DOF.
Fig. 2
This picture was captured at 8x magnification and
therefore has greater DOF.
Fig. 3
When the magnification increases, the
DOF narrows.
Selecting the focus point
Because the DOF is so restricted
when shooting under the microscope, the
focus point has to be the sharpest spot in
your picture. Before capturing an image,
it is necessary to think like a photographer and ask yourself some questions:
1. Why do I want to capture this
picture?
2. What is the point of interest in this
image?
3. What do I want the viewers to see in
the image?
4. How is this image going to be
different from others?
5. Where do I want to focus?
This is my formula: Find the things
in the image that stand out as being most
important, and place the focus point
Continued on p. 41
dentaltown.com \\ OCTOBER 2015
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endodontics
feature
Continued from p. 39
there. For example, in Fig. 5, I wanted
to capture the gutta percha in the mesial
buccal canals. Therefore, I selected my
focus point as the tiny white spot in the
DB canal. The important parts of the
picture were in focus.
Fig. 5
Working with live view
Live-view mode is a useful tool in
successful microphotography. One of the
significant advantages to using live view
in DSLR cameras is that the camera’s
internal mirror will be flipped up, allowing you to display on your LCD or monitors exactly what your camera is seeing.
Because the mirror is raised up when
working in live view, the camera does not
cause vibration of the scope, so the microscope’s bounce is decreased and sharper
images are obtained. Mirrorless and
translucent cameras always display live
view. Live-view display gives significant
help in achieving sharply focused pictures, and the assistant can confirm that
the image is centered and focused prior to
capturing the final image.
Live view also allows the photographer
to easily readjust the settings because he or
she can quickly check focus, framing, etc.
The focus point is placed on the tiny bubbles
between teeth #8 and #9 at 8x magnification.
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Fig. 7
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dentaltown.com \\ OCTOBER 2015
41
endodontics
feature
Fig. 8
For example, in Fig. 6 on p. 41, the
image is out of focus, the framing is off,
the picture is overexposed, the ISO, white
balance and the shutter speed are not
ideal. After readjusting the settings in live
view, the final result was greatly improved
(see Fig. 7 on p. 41).
Perfecting focus
Fig. 9
Fig. 10
The real key to successful microphotography is to find the precise
balance between the camera and the
microscope. In other words, the subject
that is observed through the eyepieces of
the DOM must be perfectly duplicated
by the camera, without any distortion.
Par-focal adjustment is crucial to success
in microphotography.
This desired outcome is accomplished
through correct par-focal adjustment of
the microscope. Par-focal adjustments
assure that the image is in focus under
the DOM and camera simultaneously,
and when magnification is changed from
higher to lower (or vice versa), the object
stays in focus.
However, if we follow the typical
guidelines to make the par-focal adjustments, the image as seen through the
microscope will be clear, but will reproduce as blurry in photographs. This
unwanted result occurs because the manufacturer’s par-focal procedures indicate
the use of a two-dimensional, flat target
as point of reference.
Translation of these adjustment
settings to the mouth of the patient
results in pictures that are out of focus
because the open mouth of the patient
is triangular in shape, as demonstrated
in Fig. 8, but par-focal adjustments were
made using the flat target. Therefore, it
is necessary to set the camera and DOM
using a three-dimensional target, which
recreates the position of the open mouth.
Successful setting of the DOM and camera can be accomplished by constructing
a three-dimensional focusing target that
mirrors the angles and dimensions of a
mouth-propped patient.
Finally, set the camera to center
metering mode (CMM), put the focus
point on a small dot on your custom PF
target and, working with monitors, center
the image in the middle of the screen.
Next, follow the traditional steps as outlined by your microscope company for
par-focal adjustment. Fig. 9 is an example
of a photograph where par-focal adjustment has been done incorrectly.
Fig. 10 is a picture taken with correct
par-focal adjustment.
Conclusion
Microphotography is an art, and
in order to capture the highest-quality
pictures it is necessary to understand the
obstacles that will be encountered and
how to overcome them. The photographer must achieve the perfect balance
between the microscope and camera in
order to get the desired results. ■
References
Peterson, Bryan (2010). Understanding Exposure. (3rd Edition, p.
42). New York: Crown Publishing Company
Do you have questions for the author? Ask them online at Dentaltown.com/magazine.aspx.
Author Bio
Dr. Jorge Zapata is a dentist in Ogden, Utah, who has been practicing microscope dentistry in his private dental practice since 2005. Dr. Zapata is treasurer of
the Academy of Microscope Enhanced Dentistry (AMED). He has been a member of the board of directors for AMED since 2011, and in 2014 he was a recipient
of AMED’s Outstanding Service Award. Zapata was a guest lecturer at Roseman Dental School in Salt Lake City in 2015 and was a guest speaker at the European Society of Microscope Dentistry in Berlin. He can be contacted at [email protected].
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OCTOBER 2015 // dentaltown.com