Pentax K10D vs Sony Alpha A100

Pentax vs Sony

The Sony Alpha A100 and the Pentax K10D compete head-to-head with the most similar feature set among 10 megapixels DSLR cameras. These two digital cameras share the same image sensor, built-in stabilization and dust-reduction. As a matter of fact, these are the only two currently shipping 10 megapixels DSLR cameras with built-in stabilization. Later this year, they will be joined by the Olympus E-510 which has a smaller 2X crop sensor with 4:3 aspect ratio.

Besides the lens mount, the most prominent feature difference is the Pentax K10D’s weather-sealed body. Note that weather-sealing is only truly effective when using weather-sealed lenses and Pentax has not shipped any such lenses yet. The first two such lenses, the 16-50 F2.8 and the 50-135 F2.8, are expected to ship in May 2007. Since these are moderately high-end lenses with retail pricing above $800, the weather-sealing feature may not be relevant to all buyers.

The remaining differences between the Alpha A100 and the K10D can be spit into performance features and usability features. Since these camera’s share the same sensor, performance differences were not expected to be significant.

Performance

In our full-review of the Sony Alpha A100, we already showed that the Pentax K10D produces images with noticeably more details starting at ISO 400 and slightly less noise starting at ISO 800. See this in the outdoor crops from the A100 review. Higher-than-average image noise is definitely the A100’s more serious weakness.

A camera’s performance is not simply about image noise. There are also differences in sharpness, exposure, color, speed, stabilization and dust-reduction. Sharpness is the most difficult to quantify because it depends on both the camera and the lens used. Generally, DSLR cameras produce slightly soft images by default. However, boosting the image sharpness of both the K10D and the A100 to their respective maximums clearly shows that Sony’s image processing is capable of producing much sharper images. Indeed, JPEG softness is the K10D’s most critical weakness.

Sony Alpha 100 and Pentax K10D

The exposure systems of both cameras are excellent. The main difference is that the A100 uses 40 segments for its multi-segment metering compared to the K10D’s 16 segments. In practice this translates to more consistent metering for the Sony Alpha. In other words, the A100 changes its metering less when the camera is moved around the same subject than the K10D. In terms of accuracy, both cameras meter conservatively to reduce the chances of burning highlights. That does not mean that they meter identically, since there is no generally no absolutely correct exposure for scenes which exceed a camera’s dynamic range. The images below shows a case where the A100 chose a brighter metering and one where the K10D did. This proves that neither camera is consistently more conservative than the other.

Color accuracy varies depending on light sources and a camera’s white-balance system. Both the Sony Alpha A100 and Pentax K10D showed very accurate white-balance systems when set manually. When set automatically, white-balance occasionally differs substantially. Under natural light, differences are small but the K10D consistently produced more accurate results. In artificial lighting, the K10D got slightly better results with preset white-balance but often got significantly worst results with automatic white-balance. Overall, the K10D produced better results more often than the A100 while using automatic white-balance. However, when both camera’s automatic white-balance failed, the K10D left a much stronger color cast than the A100. Therefore, those who generally leave white-balance on automatic will probably be served better by the Sony Alpha A100.

Speed is great with both cameras. They are both capable of shooting continuously at 3 FPS until the memory card gets full. The way the K10D’s shutter-release is designed makes the K10D feel more responsive than the A100. While, this difference is noticeable, it is only a minor difference. For every thing else, both cameras show excellent responsiveness and never leave the photographer waiting.

Clearly, built-in image-stabilization is the most important selling point for these two DSLR cameras. The obvious advantage to built-in stabilization is that it stabilizes all lenses. The disadvantage is that its performance is dependent on the camera. You cannot buy a better stabilized lens if the built-in stabilization is not good enough. Neither Pentax nor Sony, or formerly Konica-Minolta, produce any stabilized lenses anyway. Sony claims that its Super-Steady-Shot system provides 2 to 3.5 stops of added stability. Pentax claims 2 to 4 stops of added stability. After several hundred shots with each camera but before formal testing, the initial impression was that Sony’s stabilization worked much better than Pentax. After some Internet research, it was clear that opinions of the K10D’s stabilization are much more mixed than opinions on the Alpha A100. Therefore, more formal testing was required.

The effectiveness of stabilization is not systematically measurable because it depends on so many factors including the photographer’s movements. Instead, it must be measured empirically. For this we took shots of several targets while varying shutter-speeds and quantified the number of sharp shots. The results showed that the Sony Alpha A100’s built-in stabilization performs statistically better and more consistently than the Pentax K10D. However, the difference is less pronounced than anticipated. The table below summarizes the observed results:

Percentage of Sharp Shots
	Stop Over 1/Focal-Length
Camera	2	2.5	3	3.5	4
Sony Alpha A100	100%	100%	80%	20%	0%
Pentax K10D	100%	80%	30%	10%	0%

There is one small but very important detail which advantages the Sony Alpha A100 with regards to stabilization: the shake-meter. For the unaware, the shake-meter is a 5-point scale visible in the A100’s viewfinder, similar to its Konica-Minolta Maxxum predecessors, which indicates relative camera shake. The photographer can use the shake-meter to judge the stability of his body-motion and adjust his posture and breathing to lower the indicated shaking. As such, the A100’s stabilization can stabilize the image sensor and the photographer!

The final aspect of performance is dust-reduction. Both cameras perform dust-reduction by shaking their sensors. The difference lies in usage: The K10D has a system menu option to trigger sensor cleaning directly while the A100 has a setup option which cleans the sensor at each power-off. This meant that this Sony DSLR accumulated little dust but going through extra dust-cleanings did not improve things. This Pentax DSLR, however, accumulated more dust and going through several dust-reduction cycles reduced its appearance slightly. In relation to the size of dust particles, dust-reduction worked mostly on small dust particles, like those that can be seen at F11 and beyond. The end result is that both cameras still required manual sensor cleaning and neither was capable of getting rid of the dust that really mattered.

Usability

Usability is more subtle than performance. It includes design, ergonomics and features. Features that form part of usability are those which help photographers with the creative and technical process of photography. Among non-DSLR cameras, there are lots of features which do not fall into this category like world-clock, direct-printing, website publishing, etc. Digital SLR cameras have lots of usability features, but some manufacturers like Nikon and Pentax generally pack more of them. The Sony Alpha A100 may not have the most but it does pack several unique and very practical features.

In terms of body design, both the A100 and the K10D are rather good. The K10D and A100 have excellent hand-grips, the former being wider and the latter being deeper. Which one feels more comfortable most likely depends on the size of your hand. Without loosening pressure on the camera’s back, several important buttons can be reached using your thumb. On the K10D, those are the EC, AF and AEL buttons, although that last one may require shifting your grip a little. On the A100, those are the EC and AEL buttons. Since the Sony’s buttons are larger, they are easier to press while wearing gloves. Both these DSLRs have an easily accessible front control-wheel. Once again, the Sony’s is easier to use with gloves because it has bigger notches. This may not be an issue for most people, but if you do take pictures where gloves are required, it is something to keep in mind. Another point with regards to gloves is that the K10D’s memory and battery door compartments are more difficult to open. This is a reasonable compromise considering that DSLR’s weather-sealing.

The K10D also has a second control-wheel on its back (above the EC and AF buttons) and a green button (near the shutter-release). Both of these are put to great use and, consequently, provide more efficient access to certain functions compared to the A100. Particularly, in A and S modes, the second-control wheel can be used to directly change ISO sensitivity and the green button can be used to automatically select the ISO. The green button can also be used to reset the exposure parameters to their metered values in both P and M modes.

Sony Alpha A100 - 0.83X Magnification
sony_viewfinder Pentax K10D vs Sony Alpha A100

Pentax K10D - 0.95X Magnification pentax_k10d_viewfinder Pentax K10D vs Sony Alpha A100

The K10D’s pentaprism viewfinder is both bigger and brighter than the A100’s pentamirror one. The difference is particularly noticeable in low-light. Coverage is at 95% for both though. Both cameras also feature a high-resolution 2.5″ LCD for reviewing images. The Sony Alpha A100 has an eye-start sensor which turns its LCD off while the viewfinder is in use. This is a timesaving feature which nearly eliminates the need for the LCD activation button. Another thing that the A100’s LCD does well is that it stays on while settings are being changed. As for the Pentax K10D, its information screen disappears as soon as a setting is changed. On the other hand, the K10D has a top-mounted LCD which can be used to change most exposure settings. Some important settings, such as white-balance, cannot be seen on the K10D’s top LCD and therefore require using the rear LCD. The top-mounted LCD position is generally more useful while using a tripod but not necesarily for hand-held photography. With the Sony, all settings can be changed and seen from a single location which improves efficiency

Although basic capabilities are the same, these two DSLR cameras show different philosophies with their extended and unique features. The Sony Alpha A100 tends towards more automation addressed at various photographic situations. The Pentax K10D takes the opposite approach by providing more direct controls to the photographer.


Pentax K10D	Sony Alpha A100

The first place to notice this is on the mode dials. While both cameras feature the standard Automatic, Program, Shutter-priority, Aperture-priority and Manual modes, the Sony adds six scene modes. Each scene mode is pre-optimized to Sony’s liking for particular subjects. Instead of scene modes, the Pentax has five additional modes, including a user-programable mode. The most unique modes of the K10D are its sensitivity-priority mode and its shutter-aperture-priority mode. The former mode selects aperture and shutter-speed automatically based on a chosen ISO sensitivity. The latter selects ISO sensitivity based on a chosen aperture and shutter-speed. Note that even in aperture-priority and shutter-priority modes, the K10D allows direct access to ISO sensitivity using a control-wheel.

Image parameters can be changed directly on both cameras in terms of color-tone, contrast, sharpness and saturation. While the K10D has more steps in its image parameters, each step is larger on the A100. We already mentioned that sharpness at +2 on the A100 is sharper than +3 on the K10D. The same is true for color saturation and contrast. In addition to those direct controls, the A100 features innovative ways to affect image contrast and therefore dynamic range. First, there are special keyed ISO settings: Lo80 and Hi200. These settings have a fixed effect designed to help with low-key and high-key scenes, respectively. Second, there is the Dynamic Range Optimizer (DRO) which adjust an image’s tonality to enhance its apparent dynamic range. What is important about these features is that their result cannot be emulated by any combination of camera setting on the K10D, or any other DSLR, while shooting JPEG. However, with enough effort, they can be emulated using RAW conversion software. Speaking of RAW images, the K10D can develop them directly in camera and supports two such formats (Pentax’s PEF and Adobe’s DNG).

Although the K10D’s white-balance system is more customizable than the A100’s, its standout feature is an extremely useful white-balance preview. The white-balance preview works by taking a picture without storing it and dynamically changing its white-balance as the users modifies the camera’s white-balance settings. This allows for a very accurate selection of white-balance without resorting to manual white-balance. With other DSLR cameras, including the Alpha A100, one has to go through a trial-and-error process until the results are pleasing.

There are plenty of other differences between these two 10 megapixels DSLRs when it comes to customization. Two particularly useful features of the K10D are its Program-Line and its customizable Auto-ISO. The program-line gives control on how the Program mode chooses its shutter-speed and aperture combination. This can be customized to favor fast shutter-speeds, narrow apertures, the lens’ optimal aperture or average settings. The Alpha also has some very useful features: EC effect, AEL button customization and Eye-Start AF. The EC effect option selects whether EC affects ambient illumination only or ambient+flash illumination. The AEL button can be customized to use the set metering mode or spot metering and to behave as a hold-button or a toggle-button. Each of these options improves efficiency in specific situations. The Eye-Start AF option lets the camera start focusing before the shutter-button is half-pressed without using continuous auto-focus.

Sony Alpha 100 and Pentax K10D

The last, but not least, aspect of usability is the availability of modern lenses. Although Pentax has been in the camera business for longer, Sony currently produces more lenses. Even so, both these companies have far fewer lenses than Canon and Nikon.

To summarize, here are the relative advantages of each camera over the other. It is not the number of advantages that counts, but which ones are relevant and their relative importance to your photography. Working in RAW over JPEG, for example, greatly affects the importance of several points listed below. When choosing between these excellent cameras, keep in mind that it is your photography that decides which is best.

Finally, you should always judge image quality by your own standards. Click on the scaled image of any of our samples to see the unmodified full-resolution image, but keep in mind that results will vary according to the lens in use.

Sony Alpha A100