مطلب زیر از سایت http://www.dpreview.com نقل میشه:
I have been comparing the Pentax K10D, Sony A100, Canon XTi and Nikon D80. I have all of them here at least for a few more days - at least until I finish a few comparisons. My impressions are mostly subjective so far, but I am comparing all the cameras side by side.
VIEWFINDER: The Pentax has the best viewfinder, followed closely by the Nikon D80, then the Sony A100. The Sony viewfinder is remarkable for a penta mirror setup, but it is no match for the true pentaprisms in the Nikon and Pentax. The Canon is by far the worst of the lot in viewfinders.
AUTOFOCUS: I compared all cameras using a 50f1.4 lens, since the shallow depth of field evened the focusing playing field for all cameras. All four 10 megapixel cameras were very fast in focusing and locking on the same subjects - much better than older models like the Pentax *ist D. Focusing noise was lowest for the Canon, but it was only very slightly quieter than the Nikon D80 (with a 50f1.4D) and Pentax K10D (50f1.4 FA) which were virtually tied. The Sony was just as fast in focusing , but noisier than the other cameras with a Minolta 50f1.4 lens. Perhaps the Sony would be quieter with the reworked Sony 50f1.4 if anyone could find it (and pay the new $350 cost Sony is asking). However, this was as fair as I could make it with the 50f1.4 lenses I had available.
HIGH ISO NOISE: From limited shots so far the Pentax is also the best at controlling noise at high ISO, which was a complete surprise to me. The Canon is almost the same as the Pentax K10D, followed by the Nikon, with the Sony last. All 4 are identical to ISO 400. At 800 differences start to appear. To my eyes the Canon CMOS sensor controls noise well (but not as good as the Conon 6 megapixel and 8 megapixel CMOS sensors) but at the expense of dynamic range. Since dynamic range, the range from lightest to darkest is already a problem with all digital photography I prefer noise control that preserves the already limited dynamic range as much as possible.
BUILD QUALITY: By far, the Pentax K10D feels the most solid and it is the heaviest, a surprise again since the Nikon D80 is a pretty solid piece of equipment. The extra sealing for water/dust resistance pays off in a very solid feel to the K10D. This is easily the best quality Pentax since the *ist D, which also had a solid quality to it. I consider the Nikon and Sony build quality about the same, except for the Sony's loud slapping mirror and louder focusing, with the Canon far behind the other 3 in build quality (but quiet lenses). The damped mirror sound on the Pentax is reassuring to my ears.
CONTROL: I've liked Hyperprogram since before the old *ist D days, and I think Pentax did a really great job with the front/rear dials and new sensitivity program line. The Nikon D80 also has both front and rear control dials, while the Sony and Canon have just one control dial. I still like the Pentax ability to shift the program aperture with one dial and the shutter speed with the other. Hyperprogram makes shooting like YOU want a lot easier.
AUTO ISO: Both the Pentax and Nikon offer user selectable Auto ISO ranges - a feature I really like. The Sony Auto is limited to ISO400, which turns out to be a good match to the sensor capabilites. The K10D capabilities with a manual, non-autofocus K-mount lens are icing on the cake - you can even use effective anti-shake with manual lenses after dialing in a little info.
CONCLUSIONS: All-in-all I find the Nikon D80 and Pentax K10D the closest in build quality and depth of features. When you consider the K10D has very effective anti-shake built in, effective moisture sealing, and dust removal - and the Nikon has none of these features - the tip is definitely to Pentax for me. I still think the Sony is a great all-round camera, and with the current price about the same as the Canon XTi, the Sony is an easy choice between the two. Canon will sell a ton of XTi's to people who don't compare, but this go around the Canon is the least competitive.
I will be even happier when lenses with motors start appearing for Pentax. Pentax was smart to add this capability, but they are usually VERY slow to ship those good ideas. If they sell a ton of K10D - which they will if buyers compare - then it may come quickly. That will remove the last Canon/Nikon advantage. It was pointed out that Sony also addressed the lens motor issue with a couple of very expensive lenses, but I don't know if their plans include lens motors in any of the more common and affordable lenses
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