Clinical photography 01 /certified fixed orthodontic courses by Indian dental academy

CLINICAL
PHOTOGRAPHY
www.indiandentalacademy.com

INDIAN DENTAL ACADEMY
Leader in continuing dental education


• Ever since the caveman began drawing on
walls, it has been widely acknowledged that "a
picture is worth a thousand words."
• Nowhere is this truer than in dentistry.
• Radiography depicts that which cannot be seen
with the naked eye; photography documents
that which can be seen.

• Photography is undoubtedly one of the most
important inventions in history -- it has truly
transformed how people conceive the world.
• Now we can "see" all sorts of things that are
actually many miles -- and years -- away from
us. Photography lets us capture moments in
time and preserve them for years to come.

• Photography is a universal means of
communication and an invaluable tool in many
fields.
• From family snapshots to pictures taken from
aircrafts, photographs record the people and the
things we see, as well as many subjects beyond
our range of vision.

• In skilful hands, a camera can transform an
ordinary scene into an image of exceptional
beauty.


WHAT IS PHOTOGRAPHY?
• The word photograph comes from the greek
words ‘Phos’ and ‘Graphien’.
– Phos – light
– Graphien- To draw
• Literally – To draw with light
• Photograph is a picture drawn with light.

• The art of photography has been in existence for
well over a century.
• It is best described as an art for the purpose
that we likely to put it to; but in recent years,
it has also become a science.


WHY PHOTOGRAPHY IN
DENTISTRY??
• Patient education
– Understand her/his condition
– Need for treatment
– Visualize potential improvements
– Improves confidence
– Evaluation of progress

• Interactive treatment planning
• Diagnostic aid

• Teaching
• Publication / Clinical research
• Communication with colleagues
• Record keeping
• Legal protection


CAMER
A


• The term camera is shortened from camera
obscura, literally "dark room" in Latin.
• The camera is basically a box , with small
aperture or opening where the lens is attached
at one end and the film at the other.

• The inside of the camera must be completely
dark , so that the rays of light reach the film
only through the aperture.


PRINCIPLE
• The camera works in much the same way as
your eye.
• The lens in the eye focuses the image on to the
nerve cells in the retina and this image is sent to
the brain by the optic nerve.

• This is the principle employed in the camera.
The lens sharply focuses the image on to the
film.
• To keep the image sharp even when the distance
varies, the lens has to be moved either farther or
closer to the film. This what we commonly call
‘focussing’.

• The diaphragm of the camera is a variable
aperture which controls the amount of light
allowed onto the film, much in the same way
that the iris of the human eye contracts in
bright sunlight but opens when the room is
dark.

• The light reflects from a subject, enters the
camera through the lens, which focuses the rays
of light into an image on the film.
• Light rays from the top of the subject form the
lower part of the image and those from the
bottom form the upper part. Thus the image on
the film is upside down.

TYPES OF CAMERAS

• Single Lens Reflex (SLR)
• Twin Lens Reflex (TLR)
• Instant picture / Polaroid
• Point and Shoot
• Special cameras
– Panoramic
– Under water
– Stereoscopic
– Sub miniature (spy)

SINGLE LENS REFLEX


TWIN LENS REFLEX


COMPONENTS OF A 35mm SLR
CAMERA
Hot Shoe For Flash


LENS


• Lens is a piece of transparent material that has
at least one curved surface.
• The lens is the heart of the camera, the
component that turns the three dimensional
world outside the camera into a two
dimensional image on the film inside.

• Its job is to take the beams of light bouncing
off of an object and redirect them so they come
together to form a real image -- an image that
looks just like the scene in front of the lens.


• The best way to understand the behavior of light
through a curved lens is to relate it to a prism. A
prism is thicker at one end, and light passing through
it is bent (refracted) toward the thickest portion.


• A lens can be thought of as two rounded
prisms joined together. Light passing through
the lens is always bent toward the thickest part
of the prisms.


CONVERGING
OR
CONVEX LENS

DIVERGING
OR
CONCAVE LENS

• A lens produces its focusing effect because light
travels more slowly in the lens than in the
surrounding air.
• Therefore, refraction (an abrupt bending of a
light beam) occurs both where the beam enters
the lens and where it emerges from the lens into
the air.

• Because of the curvature of the lens surfaces,
different rays of an incident light beam are
refracted through different angles.
• Thus an entire beam of parallel rays can be
caused to converge on a single point. This point
is called the focal point, or principal focus, of
the lens.

FOCAL POINT


• Refraction of the rays of light reflected from or
emitted by an object causes the rays to form a visual
image of the object.
• This image may be either

– real--photographable or visible on a screen or
– virtual--visible only upon looking into the
lens, as in a microscope.

• The focal length of a lens is the distance from
the centre of the lens to the point at which the
image of a distant object is formed.


FOCAL LENGTH


• A long-focus lens forms a larger image of a
distant object, while a short-focus lens forms a
small image.


• The closer that you move an object to the lens, the
larger it will appear on the film or photograph.


• The image may be much larger or smaller than
the object, depending on
– the distance between the lens and the object
and
– the focal length of the lens .


• There is a limit to how close you can move an
object in order to enlarge an image size.
• If you move too close to an object, with a lens
which is not suited to that distance, then the
image will get distorted.
• This is one of the most important concepts in
dental photography, with regard to lenses.


TYPES OF LENSES

TYPES OF LENSES
• Fisheye lenses
– The fish eye is an ultra wide angled lens.
– Typically it will have a focal length of
between 6 and 16 mm
– For shooting interiors or other confined
spaces where an extreme angle of view is
needed

Wide-Angle Lens
– Includes focal lengths ranging from around
15mm through 35mm
– Particularly well suited to landscapes and
architectural photography


Normal / Standard lens
– 50mm lens
– Suitable for all general photography
– Usually are the cheapest available for
cameras


Telephoto lens
• Short telephoto lenses range from 85mm to
250mm.
• Long telephoto lenses range from around
300mm to 1000mm, and beyond.
• Both these groups have multitude of uses
including landscape photography, sports
photography and wildlife photography.

• In addition, a short telephoto lens is considered
ideal by many photographers for portrait
photography.


Zoom lenses
• Designed to have variable focal length from
24mm to 80mm, or 80 to 200mm, etc.
• These are very handy pieces of equipment for, in
one lens, you get two or three normal lenses.
• Expensive, but when you consider that they
take the place of two or three lenses these are
quite economical.

50mm

120mm


300mm

Macro lens
• Macro-photography is a term that covers the
photography of subjects on a life size scale (1:1)
or larger than life size perhaps up to ten times
(1:10).


• Macro lenses offer a stepless range of
magnifications and shooting distances.
• They make good portrait lenses.


• Dental Photography: 100-105mm Macro lens
• Some zooms can be set at a macro setting,
although the image magnification is not as
great.
• In addition, because of the variable focal
ability, it is almost impossible to make zoom
lenses as sharp as a fixed focal length macro
lens.

• Depending on the preference of the
photographer and the situation, a wide variety
of choices can be exercised in order to get the
required effect from the lens.


SHUTTER SPEED


• The purpose of the shutter is to protect the film
from light until the chosen moment.
• Simply put, the shutter speed is the length of
the exposure time.


• Shutters have speeds ranging from ½ sec. to 1/8000
sec.
• A fast shutter speed, 1/2000 sec., 1/4000 sec., etc means
that the shutter is open only for a brief moment.
• A slower shutter speed, 1/30 sec., ½ sec. means the
opposite; the exposure is made for longer.

• Do not let the numbers on your camera confuse
you.
• A shutter speed shown as ‘2000’ means
meaning very fast.

1/2000

–

• The fraction indicator of 1/ is left out to
‘simplify’ things.

1/30

1/1000


• Each speed will allow half as much of light
strike the film as the preceding one.
• For eg.
– 1/30 will allow twice as much light as 1/60 would.


MECHANISM


• Usually, in Dental Photography, we have
standard situations which are static. Therefore,
the shutter speeds are also standard viz. 1/60


APERTURE


• The aperture is an opening through which the
light passes from the subject to the film.
• The aperture size is a measure of the size of
that opening.
• It controls the amount of light that is allowed
to pass through the lens, and eventually strike
the film.

• The aperture does this either by opening or closing ,
and allowing more or less light to pass through.


• Some lenses have a
rotating ring on the lens
barrel
called
the
aperture selection ring.
• Other cameras have an
electronic dial to control
this setting.

• The various sizes of the aperture are called
‘f’ stops or ‘f’ numbers.
• The f-stops start from 1.4 and go up to 32.
• Easy calculation:
1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32

• These numbers refer to the size of the LENS
aperture, but not the diameter of the aperture.
• The f number is the number by which the focal
length of the lens must be divided to yield the
diameter of the aperture


• For eg.
– In a 50mm lens the lens is set to f/2 aperture.
– Therefore the diameter of the aperture must
be 50/2 i.e. 25mm.
– Similarly, in a 100mm lens an aperture
setting of f/2 means a diameter of 100/2 i.e.
50mm


• Caution:
A 50mm lens set at f/8 will
allow exactly the same
amount of light that is
allowed to pass through
as does a 200mm lens set
at f/8

200mm


50mm

• This can be expained on
the basis of the Inverse
Square Law.
• The intensity of light is
inversely proportional to
the square of the
distance that it travels.

200mm


50mm

• The 200mm is longer
than the 50mm lens.
• Therefore the light has to
travel further to reach
the film.

200mm


50mm

• Thus, on the 200mm lens
the opening has to be
bigger, at f/8, to allow
the same amount of light
as a 50mm lens set at
f/8.

200mm


50mm

• Remember in this case too, the higher the
number, the lesser the amount of light that is
allowed to pass through.
• Also one setting allows only half as much light
as the preceding one would.

• For eg.
– If you ‘open up’ the setting from f/11 to f/8
the aperture admits twice as much light
– If you ‘stop down’ from f/11 to f/16, the
aperture admits half as much light.


FILM


Types
• Black & White
• Colour
• Colour reversal (for slides)
• Also, Instant film (Polaroid)


Speed
• Film speed is the amount of time required for
the film to react to light.
• The photographic film is similar to the
radiographic film in this respect.
• The photographic film is also composed of light
sensitive grains (silver halide particles), which
when exposed, produce an image of the subject.

• Thus, the larger the grains, the more sensitive it
is to light. This is called a fast film.
• A slower film would have smaller crystals, that
are less sensitive to light.
• However, smaller grains i.e. slower films
always would produce sharper images vis-à-vis
faster films with larger grains.

• Previously, film speed was either denoted with
an ASA (American Standards Association)
Number or a DIN (Deutsche Industrie Norm)
Number.
• Now film speed ratings have been standardized
and are indicated by an ISO (International
Standards Organization) Number.

• The film speeds available range from ISO 25 to
ISO 3200.
• ISO 25 being the slowest and ISO 3200 being
the fastest.


• Slow (25- 64) films are used for stationary
objects in a well illuminated scene or when fine
detail is essential.
• A fast film (400- 3200) is used for scenes that
have dim light or involve fast action.
• A medium (100-300) speed film is suitable for
average conditions of light and movement.

• In this case too, as you move from one film
number to the next, you would require twice as
much light to get the same exposure.
• E.g.. When you move from ISO 50 to ISO 100,
you need half as much light for the ISO 100 to
get the same photograph.


• For dental Photography, the ideal film would
be ISO 100 that provides adequate sharpness
and detail.
• Light would not be a constraint in these
situations as the conditions are static and well
illuminated with a flash.

EXPOSURE


• Exposure is the total amount of light reaching
the film in the camera.


• If too much light enters the camera, the film will be over
exposed and the picture will be too bright.
• If there is insufficient light, the film will be under exposed
and will result in a dark uninteresting picture.

• The three factors that affect the exposure are
– Aperture setting (smaller number)
– Shutter speed (smaller number)
– Film speed (larger number)


• To obtain the correct image for your object, you
must combine the three so that the correct
quantity of light strikes the film.
• Usually speaking, the shutter speeds and the
aperture are variable, but the speed of the film
is not.


• E.g. on a bright day, for a ISO 100 film the
ideal settings for a static object are f/22 and
1/60 sec.
• You need to shoot a fast object coming your
way and change the shutter speed to 1/125 sec.
Then you would need to compensate the
aperture setting to f/16 for the correct exposure.
• Vice-versa for aperture change.

• On a cloudy day, you may be better off loading
a ISO 400 film rather than a ISO 100 film.
• This would give you greater latitude in terms of
selecting the shutter speeds and aperture
controls.
• Probably the sharpness may be compromised to
a limited extent, but the trade off is worth it.

DEPTH OF FIELD


• A photographic term, which defines what is in
focus within your shot, both in front of, and
behind your point of focus.
• In other words , it is the zone of the ‘in-focus’
elements in front and behind.

Factors affecting DOF
• Aperture size
• Focal length of the lens
• Distance of the subject from the camera


• It should be noted that the depth of filed does
not extend equally in front of, and behind, the
point of focus.
• As a general rule, the DOF produced by a
particular lens will extend approximately onethird in front the point of focus, and two-thirds
behind.

1.4

4

22

8


• So how do we know what is in focus?
Most 35mm SLR’s have a depth of field
preview button.
Looking through the viewfinder with the DOF
preview button pressed down will give you a
very good idea what is in focus and what is
not.

FLASH & LIGHTING


• The two most important sources of light are
– Natural
– Artificial / Flash


•Using different combinations of the two can
enable the photographer to obtain a wide
variety of results, often with dramatic effects


Hard Light

Soft Light


• In dental photography, the flash gun is always
employed, irrespective of the type i.e. I/O or
E/O photography.


TYPES OF FLASHES


Built-in flash


Dedicated point flash


Ring flash


Ring + Point Combo


Important characteristics
• Flash guide number- indicates how powerful
the flash is.
– A GN of 40 is adequate for dental
photography when using an ISO 100 film
• Recycle time: 5-10 secs

Synchronization
• The duration of the electronic flash is very
short, often less than 1/1000 second, and it
goes off instantaneously.
• Hence, flashes can be used at shutter speeds
slow enough for the whole film to be exposed
simultaneously.
• This is where flash synchronization comes into
the picture.

• If your shutter is adjusted to higher speeds as
prescribed by the manufacturer, you may end up
with partially lit photographs.
• The shutter speed that is synchronized with the
flash is often marked in red or has this sign
marked next to it “ ”.
• This shutter speed should be the one selected
for dental photography.

Red-Eye
• We've
all
see
photographs where
the people in the
picture have spooky
red eyes. Where do
the red eyes come
from?


Red-Eye
• The red color comes
from light that
reflects off of the
retinas in our eyes what you see is the
red color from the
blood
vessels
nourishing the eye.

Eliminating Red-eye
• Many cameras have a "red eye reduction "
feature. In these cameras, the flash goes off
twice -- once right before the picture is taken,
and then again to actually take the picture. The
first flash causes people's pupils to contract,
reducing "red eye" significantly.
• Another trick is to turn on all the lights in the
room, which also contracts the pupil.

• Red-eye normally occurs when the angle of the
light, striking the subject and being reflected off
o
the camera is 2.5 or less. Thus, if possible, move
the flash away from the camera.
• You can also try bouncing the flash off the
ceiling if that is an option.
• Have the subject look slightly away from the
camera.

Leader in continuing dental education


Clinical photography 01 /certified fixed orthodontic courses by Indian dental academy

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