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Old Mar 28, 2011, 1:23 AM   #1
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Default Frustrated by Lens Decision. Need advise

Just to give you some background info, I was formerly using the Olympus E520 and the ZD 70-300 for birding purposes because it was light enough to give me 600mm reach without sacrificing portability.

When I switched to Pentax K-r a few weeks ago, I was looking for something to match the 600mm reach of the Olympus system. As I plan to use the K-r for birding as well as family and indoor events, I got the Sigma 17-70 f2.8-4.5 and the DA 60-250mm f4. I figured that by matching the 60-250mm with a Kenko Paf 1.5X teleconverter, I should be quite ok instead of spending more to get another lens just for birding.

Unfortunately, I tried the 60-250mm plus Kenko 1.5x combination last Sat during a family outing. The result was disappointing. On average, the camera could not give me a focus lock 4 out of 10 tries. Sometimes after pressing the shutter release for a few times, it achieves focus out, and somrtimes it doesn't.

Sigh...if this is the case, seems that I won't be able to use it for birding very well. What should I do now?

1) Should I save up (sigh) and get the DA 300mm f4 to match with the Kenko 1.5x? If so, will I still have the focus lock problem?

2) Or should I just forget about the kenko 1.5x and get a Sigma 120-400mm instead?

3) Or should I try to look for the Pentax AF 1.7x, which is relatively expensive almost impossible to find?

Your advise is much appreciated.

Last edited by calvinlo; Mar 28, 2011 at 1:38 AM.
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Old Mar 28, 2011, 8:14 AM   #2
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Hi calvinlo,

I personally use the Pentax F 1.7x AFA and 300mm lenses for birding, and I think I do pretty well, but the AFA takes some getting used to and though many like it, some don't so it's a YMMV thing.

The easy answer is to get either the currently available Sigma 120-400 or its two predecessors, the Sigma 135-400 or Tokina 80-400 f4.5-5.6 AT-X. Both of these lenses were discontinued a few years ago, so are only available on the used market.

One of our members, penolta recently posted a comparison that I think eventually included all three of these lenses. . .

http://forums.steves-digicams.com/pe...120-400-a.html

A number of members like the "Bigma" the Sigma 50-500, but it and its little sister the 170-500 are both pretty big lenses, and might not suit you. The new "Bigma" has HSM and OS so it's quite a bit more expensive, but it should be considered.

I've posted a number of times about the benefits of the AFA and 300mm lenses, but the posts seem to have gotten lost in a server crash. I think I may have copies somewhere on one of my hard drives. If your interested, post here and I'll try to find one -- it'll be long, and probably a bit confusing, but it'll have some good information.

I would tend to recommend against the DA*300 for use with the Kenko 1.5x, as I have had similar experiences with my Tamron 1.4x and SDM lenses, but some have said that this combo works, so you might get lucky. Both the Kenko and Tamron PZ TCs were discontinued before the first SDM lenses were introduced, so the fact that they have common electrical contacts do not guarantee that they will function correctly as an SDM TC as you have found.

Scott
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Old Mar 28, 2011, 8:40 AM   #3
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I've thought about trying to get a Kenko/Tamron PZ 1.4 for my DA 300, but as Scott says, it seems like a hit-or-miss type of thing for them working with AF. I love my DA*300, it's an awesome lens on its own, by the way. While I would really like a 1.7AFA, they've gotten too expensive for my limited use. I've been thinking that if I want something longer I should go with the Sigma 150-500, but I'm going to buy at least 1 and probably 2 different lenses before I think about anything longer than 300.
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Old Mar 28, 2011, 9:58 AM   #4
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Hi Scott, thanks for the advise about not getting the DA 300mm. I think the price of the lens is too high to take another risk of it not working well with the Kenko.

Therefore, seems that the right decision at the moment will be to forget the kenko and just get the Sigma 120-400mm. At 1.7kg, I think it is still quite portable. I agree that the Sigma 50-500mm OS HSM is good choice as well, though a monopod will most likely be necessary.

IMHO, I also think the Pentax AF 1.7x is a good option as well, but unfortunately it's hard to find, and usually priced too high.

Last edited by calvinlo; Mar 28, 2011 at 10:05 AM.
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Old Mar 31, 2011, 12:54 AM   #5
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Just to update you guys.

I just managed to secure a Pentax Af 1.7x adapter at a reasonable price. Will be getting it tomorrow.
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Old Mar 31, 2011, 11:08 AM   #6
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Quote:
Originally Posted by calvinlo View Post
Just to update you guys.

I just managed to secure a Pentax Af 1.7x adapter at a reasonable price. Will be getting it tomorrow.
These days like that is like winning the lottery. I have given up even looking of late. $500 is not worth it, I'll just save up for a fast AF lens at that cost.

John
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Old Mar 31, 2011, 2:10 PM   #7
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Congrats! I'd love to run across one at a reasonable price, I have the A*300 and it would be fun to use it with the 1.7 AFA.
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