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03-02-2008, 04:50 AM   #1
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Auto Focus - a bit of common sense

I have a K100D which behaves exactly as I expected.
Brightly lit subjects containing reasonable internal contrast auto focus very quickly.
Landscapes focus at infinity in daylight and in low light you would normally maually focus at infinity - eg firworks display. People at low light take some time to focus but organising them takes longer. Moving subjects are panned with manual or autofocus depending on light unless you want motion when critical focus is not an issue.
You get the drift - you have to be the photographer and make decisions to get the photograph you want.
I used a Canon 40D last week in both low light indoors and bright sunshine outdoors. The focusing speed and accuracy was no different from my K100d. Where the K100D hunted for focus so did the Canon and comments from high end Nikon users admitted the same behaviour.
Its not the camera. The technology relies on the same physics.
Where did Pentax get a reputation for deficient auto focussing?


03-02-2008, 05:55 AM   #2
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I have both a Canon and a Pentax. The Canon is far better in the AF department. It isn't a reputation, it is a fact of life.

True, if you go dark enough, there isn't an AF system that will save you, however, Canon and Nikon can AF better at a lower EV then the Pentax. But all AF systems have their limits.

In bright daylight, the Pentax does AF slower, but that is due to the lenses that have no built in motors. A screw driven motor in the body can never beat a dedicated fast motor in the lens. That is a factor of physics. I know as my Canon 20D can out AF my Pentax K10D anytime I decide to compare them. It also has far better software that allows the Canon to track small moving fast objects with greater ease then the Pentax system.

With that said, the Pentax AF isn't that bad. It is more then adequate for most photo opportunities. However, the truth of the matter is this...if you do wildlife/action/sport photography, you will notice the benefits of the faster AF from most other brands over the Pentax. Don't be fooled by anyone who states that the Pentax is more accurate either. I have yet to notice this from using both systems. All AF systems are fairly accurate, otherwise it would defeate the purpose of having AF to begin with.

Pentax does have many different strengths other then their relatively slower AF system. For instance, have you tried to manually focus AF Canon and Nikon lenses? Here is another factor that many people seem to forget or neglect. One of the reasons why Nikon and Canon autofocus so much faster is their lenses are designed with a shorter focusing throw. This allows the camera to zip them to and fro rather quickly. I have noted that the Pentax lenses I do have are designed with a longer focusing throw. This facilitates manually focusing them, which the Pentax excels at compared to most competition out there. This is another physical design reason why the Pentax system isn't as speedy in the autofocus department.

Just my opinions based upon personal experience from owning and using both systems. When I go out birding, I take my Canon as I can plainly see the advantage to that (I don't have to do trap focusing, etc). When I do all else, I usually take the Pentax.

What I find interesting, is why do people fail to realize that there are no perfect camera systems out there. They all have their pros and cons. It is a fact of life that Pentax AF system isnít the best in the business. It does the job, and for most situations, it does it very well. However, you cannot compare it to what the competition has. Likewise, an AF system does not make a camera. It is just one piece of the puzzle.
03-02-2008, 06:18 AM   #3
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Original Poster
Totally agree with this.
I guess most new Pentax DSLR users came from the Point & Shoot world.
No history of manual focus.

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