(Approx. 1,286 words)
What Do You Use To Frame Your Digital Images
By Fran Damratowski, Refurbishing
SIG Chair, Chesapeake PC Users Group, MD
www.chesapeakepcusersgroup.org
Refurbishing(at)chesapeakepcusersgroup.org
Obtained from APCUG with the
author's permission for publication by APCUG member groups.
When using a 35mm camera
photos are framed using a viewfinder. One of two basic types of viewfinders is
used. One type used by single lens reflex (SLR) cameras is a through the lens
(TTL) optical viewfinder. The SLR TTL viewfinders use a mirror and pentaprism
or porro finder to reflect the light/image directly through the lens to the
viewfinder without changing the light/image (what you see is what you get). The
second types are optical viewfinders that do not project the actual image
directly to the viewfinder. They are (1) rangefinders that use the principle of
triangulation and mirrors and (2) optical tunnel viewfinders that consist of a
tunnel that goes from a small lens, near the photographic lens, and the
viewfinder. The problem with the optical viewfinders is parallax error. What
you see is not exactly you get because the complete image does not come through
the camera lens to the viewfinder. What you see is actually less than what you
get.
Digital cameras have several
different types of viewfinders, optical tunnel viewfinders as described above
and TTL viewfinders. There are three types of TTLs liquid crystal displays
(LCDs) that are located on the camera, Electronic Viewfinders (EVF), and the
mirror and pentaprism or porro finder that are used in digital single lens
reflex (DSLR) cameras.
An LCD panel is essentially
a small TV built into the digital camera. The camera has a lens that admits
light to an image sensor that converts it to data. The data is then sent to a
mini computer in the camera that sends the data as an image to the LCD panel.
The LCD panel is as active as a TV screen and changes as the image in front of
the lens changes. What you see is what you get when you click the shutter
button.
An EVF is basically an LCD
panel, about 0.5 inches diagonally, located behind the small viewfinder on the
back of the camera. The image that is seen through this eye level viewfinder is
exactly what is seen on the LCD panel and will be captured when the shutter
button is clicked.
DSLR cameras use the same
the mirror and pentaprism or porro finder that are used in 35 mm SLR cameras.
Very few of DSLRs use an LCD panel to frame the photo. The LCD panel in most
DSLR cameras is used to view the image after it has been captured to the memory
card.
Advantages and Disadvantages
of the various types of viewfinders
Because LCD panels are TTL
viewfinders they have the advantage of showing about 100% of the image that
will be captured when the shutter button is clicked. There is no parallax
error. You can immediately see the effects of zooming in on your subject. It is
excellent for accurate framing. If you use an extension or a filter on the
camera lens you will see the effect of the extension or filter. You can view
the images and immediately delete those you don’t want to keep. You can also
view the camera settings if you desire. The LCD panel works well in dim light.
One of the major
disadvantages is that they generally perform poorly in some situations such as
when reflections and glare are present and in bright sunlight. The image is
also difficult to see on monitor in some dark situations because the human eye
can see about twice the light the LCD portrays. Some of these problems can be
corrected with antireflective coatings, trans-reflective technology that
increases brightness provides better contrast, and wider viewing angles.
Some LCD panels are better
than others. Larger LCD panels are easier to see than smaller LCD panels, but
to place a 2.5 or 3-inch LCD panel on a camera you must have a large camera or
give up the option of an EVF or optical viewfinder. Digicams without an EVF or
optical viewfinder are less expensive to manufacture. LCD panels are made up of
pixels. Poor quality LCD panels will have fewer pixels and may have a lot of
digital noise (bad pixels). A better LCD panel will have more pixels, but it
will use more power. See the manufacturers specifications for the number of
pixels on the LDC panel.
LCD panels use backlighting
consequently they use a lot of power. If the LCD panel is left on for a long
period of time it will drain the battery very quickly. This in turn translates
into lost pictures because there is no power or additional cost for extra
batteries.
Most Digicams have the LCD
panel located on the back of the camera integrated into the camera body. The
first consumer digicam with an LCD panel was the Casio QV-10 released in 1995.
This camera had an articulating body. Insert image of
QV-10 Cameras with articulating bodies and articulating screens are
still being manufactured today. With these cameras pictures can be taken from
any angle such as overhead, out a window, pointing the camera at the subject
but looking in another direction. Insert pictures of
Nikon with articulating body and Canon with articulating screen.
The main advantage to a
digicam with an EVF is that it is TTL focusing there is no parallax error when
looking through the viewfinder. What you see is what you get. An EVF or optical
tunnel viewfinder is a necessity if the LCD panel fades out in the sun or the
battery power is low. If the digicam has a zoom power over 5X the EVF is the
only eyelevel viewfinder available. The tunnel optical viewfinder is not an
option.
The disadvantages of an EVF
consist of slower reaction to changing views, the resolution is lower than an
optical viewfinder, because it has an LCD it uses battery power, and it freezes
between shots with rapid sequential shooting.
The old optical tunnel
viewfinder has several advantages the first is that it always works, it uses no
power and, light goes directly through the camera without changing just like
the optical TTL viewfinder in an SLR. The optical tunnel viewfinder is ideal
for someone who likes to hold the camera to the eye to shoot a picture.
Because the optical tunnel
viewfinder does not use the photographic lens about 85% of the image is not
seen, parallax error, as a matter of fact the closer to the subject the
greater the variance from the photographic lens. The optical tunnel viewfinder
should not be used when shooting a picture of the sun because there is nothing
to protect the eye.
The optical tunnel
viewfinder and EVF are omitted from many cameras because the cameras can be
smaller and it is less expensive to manufacture them.
An
LCD panel is made up of a white backlight that changes color as it passes
through a crystalline material. It is the power hungry backlight that depletes
the battery power. A new type of panel being investigated is the organic light
emitting diode (OLED). The OLED is carbon based as opposed to the crystalline
material used by the LCD. The carbon-based molecules can be sprayed on any
material and do not require a backlight that makes OLEDs more power efficient,
brighter, and with a wider angle of view. From a marketing standpoint an OLED
is less complicated and less expensive to manufacture.
This
article has been provided to APCUG by the author solely for publication by
APCUG member groups. All other uses require the permission of the author (see
e-mail address above).