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 paper5). 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 ColorVisionTM, 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