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s_arena

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Posts posted by s_arena

    buying a used 50-135mm

    in Pentax

    Posted

    <p>I would not buy a used DA* 50-135. First of all, the owner may be selling it because of an intermittent SDM. The warranty is too short, and the lons is very slow to focus. If you are insistant on buying this lens, I would buy it new with an extended warranty. I had two of these lenses. Both had SDM failure over time (one was the DAY before the warranty expired. After the second one went bad, I got it replaced and then sold it promptly. </p>

    Pentax SDM vs. Sigma HSM - speed?

    in Pentax

    Posted

    <p>I used to shoot a lot of basketball, and I remember how frustrated I would get using the 50-135 on my k-20d and then k-7. I found I needed to switch to screw drive primes to get AF speed I could live with. I agree with Martin about Pentax AF speed, as well as SDM. I have since had an opportunity to test an EOS 550D (t2i) as well as a 7D in a variety of environments. The AF speed and accuracy was so much better on the EOS cameras equipped with ring-USM lenses, that it is hard to go back to shooting Pentax. Someone posted a video on youtube that shows a 20-year old EOS camera with an old kit lens focuses faster than a new k-7 with a kit lens. (search for Pentax vs Canon on youtube). I could live with it for most situations though.<br>

    One thing is for sure; I have owned my <em>last</em> SDM lens.</p>

    Perigree Moon tonight

    in Pentax

    Posted

    <p>Full moon is actually the worst time to photograph the moon. The direct reflection back to earth eliminates the shadows that give the surface features contrast. Often pictures taken of the moon at full moon look soft and out of focus, but it is just the lack of surface detail contrast.</p>

    Beginning of the end for Pentax 35mm?

    in Pentax

    Posted

    <p>I have have heard predictions about Pentax's demise for many a year. The thing that has me a bit worried now, is that when those predictions were made in the past, does anyone remember them being accompanied by such broad complaints about quality control? Photozone now talks about lack of quality control of Pentax lenses being "a bit of a tradition" now? (I guess that is based on recent tests)<br>

    I always remember the predictions of demise based on arguments like: "great cameras and lenses, but they are just to small to compete with the big 2" etc. etc.<br>

    Does anyone remember things differently?</p>

    kx v canon 7D what is going on here? Is this stopping us upgrading?

    in Pentax

    Posted

    <p>Bill,<br /> Unfortunately those of us who had only been comparing Pentax AF systems over the years have been blind to just how good the competition is. Sure the k-7 AF is much faster than the k20d, but that is like saying Mo is smarter than Curly (Three Stooges reference.) I recently used a Canon 7D with a couple of ring-USM lenses, and I can honestly say, it made my k-7 feel like it was the 1980's. I found this video that illustrates some of the differences. It is consistent with my experience:<br />

    <p> </p>

    kx v canon 7D what is going on here? Is this stopping us upgrading?

    in Pentax

    Posted

    <p>I agree with Orlando. The k-x may have good iso performance in darkness, but unfortunately to realize the benefit you also have to be able to <em>focus</em> in that darkness...<br /> The Canon 7D combined with a ring-USM is by far the fastest and most consistent AF system I have ever experienced. Even in dim lighting with no assist lamp. Makes my k-7 seem like it came out of the 1990's.</p>

    SDM problem: could it be thick lube?

    in Pentax

    Posted

    <p>Interesting Orlando. I have read several places, including several posters here, that SDM is a "micromotor" design. Not micromotor in the traditional sense. Micromotor, in the way that Canon defines it. Canon has ring USM which goes around the lens barrel, and micro USM, which is an ultrasonic motor, but it is geared into the lens drive. My understanding is that SDM is similar in design to Canon Micro USM that is used in Canon's less expensive lens. They are ultrasonic, but not full ring-type.<br>

    Do you know for a fact that SDM is designed like the full ring drive USM? You are the first person I have ever seen write that.</p>

     

    SDM problem: could it be thick lube?

    in Pentax

    Posted

    <p>My experience has been very similar to Bulent on my DA* 50-135. I have gone through 2. One thing I don't understand: apparently Canon pioneered the use of USM lenses in 1998 and has been developing ring-type ever since. They only use micromotors on the cheapest of their cheapest lenses. Why did Pentax choose to saddle the DA* lenses with a micromotor design?</p>
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