Konica Minolta SLR - Manual (Page 7)

Pentax *istDs (Pentax Corp., Tokyo, Japan). This
camera uses the same sensor as the Nikon D100.
However, in contrast to the latter camera, the Pentax
images were strongly biased towards red. The camera
was also very ‘trigger happy’ causing multiple unwanted
exposures. The intra-oral exposures were good once the
initial change from factory preset to manual (f522) had
taken place. However, taking extra-oral views required
changes to the aperture settings. The viewfinder was the
largest of all cameras tested, but only mid-range when it
came to brightness. The camera is comparatively small
and was the lightest tested with 1324 g (including
macro-lens and flash unit).
The camera was tested with a Pentax 100 mm macro-
lens and Pentax AF 140C flash. The latter proved not
very powerful, so great care has to be taken not to move
too far from the patient for extra-oral views. Also the
recharge time was the slowest at 9 seconds.
Discussion
Ease of use
No camera matched the benchmark, the ‘Yashica
Dental Eye’, in terms of user friendliness. This bench-
mark camera requires four actions to take good images:
N Switch camera on;
N Choose magnification;
N Move forward/backward until object is in focus;
N Expose.
Ease of use is particularly important for auxiliary staff,
who may have had little previous training for dental
photography. Only the two Olympus cameras matched
the above benchmark parameters after alterations of the
initial factory settings were made. All other cameras
needed a change of aperture settings between intra- and
extra-oral photography. It is interesting to note that
instead of changing the aperture from f522 to f58
between intra- and extra-oral images, one could also
change between modes: from aperture priority to
‘manual’ or ‘portrait’ mode as these modes often
automatically change the aperture. However, this was
not consistent between manufacturers. As changes were
necessary for all models (apart from Olympus) changing
the aperture is recommended.
Color reproducibility
Measuring color is complex—there are several systems
available to aid this process. To our knowledge only one
has been published regarding the impact of color fidelity
in orthodontics.
4 In analogue photography, color
fidelity was largely determined by the make of film,
but the flash unit, as well as the lens used also
contributed. In digital photography mainly the sensor
and the subsequent processing of the data determine the
color of the image. The difference in color reproduction
for digital cameras reflects the manufacturers assumed
customer preference for color weighting. The Fujifilm S
3 Pro exemplifies this best: the camera has two ‘film
simulation modes’, which allow the operator to choose
the weighting of colors. Generally, color profiling
cameras is often only achievable for specialist equip-
ment: even professional 36 mm SLR cameras edit or
‘color render’ images (ISO22028-1), thereby interpret-
ing/assuming the characteristics of a pleasing appear-
ance of the image. The color rendering will, among other
things depend on the format they are taken in (by
example JPEG or TIFF): the camera acts as a computer
‘translating’ the images on the sensor into the respective
format. In most ‘prosumer’ and all professional cameras
the user is able to bypass this process by downloading
‘RAW’
(unprocessed) images to the computer.
However, even when taking images in ‘RAW’ mode
some rendering will take place in the software used to
produce the images on a screen or printout. To undo the
‘rendering’ would therefore remove the images’ intended
characteristics. This investigation therefore abstained
from ranking the color reproducibility of the images and
only used descriptive terms to characterize the color
reproduction (for further information, see International
Color Consortium white paper
5 ). Color adjustments will
have to be made for all cameras to produce images
matching the original object for color temperature.
In addition, for ideal reproducibility of color on
monitor and printer, an elaborate calibration process is
required. Monitors needs to be regularly re-adjusted as
color may change over time. For printers the color
fidelity may vary for different print-media and may also
vary with each new print cartridge. In this investigation,
‘SpyderPRO’ by ColorVision
TM , a combination of
hard- and software was used, which allows the monitor
to express the original color generated by the computer,
to a high standard. However, even after monitor and/or
printer have been calibrated, in the end, direct compar-
ison between the object itself and its image will be
necessary. Although color temperature can be mea-
sured, the figures themselves should be treated with
caution, since a difference in the measurement does not
necessarily reflect an equivalent change in the observer’s
perception. This final comparison between the object
and the image will depend on a variety of factors: the
temperature of the ambient light, temperature and
humidity of air etc. It is also worth remembering that
about 7% of male and 1% of the female population in
Journal
of
Or
thod
ontics
JOR
3338.3d
11/7/0
6
19
:17:41
The
Charlesworth
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Rev
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JO September 2006 Features Section Comparison of digital SLR cameras 7