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02-18-2013, 05:53 AM   #1
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Sharp tele zoom working with K-01

Hi all,

I just cancelled the order of the Tamron 70-200/2.8, as I read about many AF problems with the K-01.

Now I am back to filed one. I am looking for a telephoto lens for the K-01. It should not be more than 800$ and have auto focus. And, most important, evenly sharp to the edges of the frame when stopped down to f/8 at least up to 200mm, even when looking in the 100% view, and no purple fringes. Basically just what my Tamron 17-50/2.8 does at f/5.6 and f/8. One can easily print the picture in 20x30" and look at the corners from close, without immediately seeing the corners are soft.

I owned a 50-135/2.8 some years ago, it was just sharp enough at f/8 (but bad at f/4 and f/5.6), but had quite obvious purple fringes problem towards the long end, even if stopped down to f/8. 135mm is quite short, too.

Any idea which other lens could do the job? The Tamron 70-300 VC isn't available for Pentax, the 55-300 I owned was just soft towards the borders of the frame, even when stopped down.

02-18-2013, 07:10 AM   #2
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First there were indeed some AF issues with some zoom lenses with the original firmware. The latest firmare update is a MAJOR improvement from firmware 1.0. I cannot comment on your specific zoom interest. But I use the K-01 with the DA18-135mm and DA18-250mm. I had some issues using the DA18-250mm with firmware 1.0 and they are resolved now.

If you have not done it yet, please do update the firmware of your K-01. It is worthwhile.

My 5 cents....
02-18-2013, 07:26 AM   #3
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Do you really need it to be a zoom? Also, if the lens has quickshift, you can easily focus manually with focus peaking, in case AF is taking too long
02-18-2013, 08:25 AM   #4
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My pentax DA 50-200mm works great with my k-01.

02-18-2013, 08:44 AM   #5
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I too would consider the 50-200 if that's enough reach; copies can be found cheaply so it's not much risk. My copy was reasonably sharp and its bokeh was consistently good. The 55-300 is an excellent zoom for its price range, it knocked the 50-200 out of my lineup - but it's bulky and awkward for me on the K-01.
02-18-2013, 10:28 AM   #6
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I owned both the 50-200mm and the 55-300mm. I used them on a K-5. Non of them was really great in boarder sharpness.

The question if it really has to be zoom is a good question. Well, I'd love to have one lens only beside my 17-50 for the kind of things I'd like to do. On the other hand, if it is two primes and they are quite small, it might work, too. The goos news is: I already have the 70mm Limited and it is sharp enough to crop up to 85mm for the print size I'd like to get. Now, a factor of 1.5 would be OK, it shouldn't be less, as only one lens is left. So I automatically end up at 135mm. This leads to the question: The SMC-F(A) 135/2.8, when stopped down, are they as sharp as the 70mm Limited is? Well, if I go for primes and accept being less flexible, the quality should be even higher.

The other thought is the Sigma 50-150/2.8.
02-22-2013, 05:47 AM   #7
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Hmm, the old Sigma 50-150/2.8 is hard to find, the new one not available for Pentax.

So in the end, it will be one of these three:

Pentax SMC-F(A) 135/2.8 (if I find one)
Sigma 70-300 OS
Tamron 70-300

Non of the Zooms is 100% convincing in the sample pictures I got, but it is quite close to be convincing, at least up to the 200mm I'd like to get. And they are cheap, so it is acceptable they only bring 90 or 95% at the border of the picture. I owned a Nikon 55-300 VR, on the D2x it was just doing the job perfect up to 180mm. The Sigma OS 70-300 is just a little bit softer than the Nikkor is, not really big difference.
02-23-2013, 12:37 AM   #8
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I'll go for the cheap Tamron. It seems up to about 200mm it is doing AF without problems on the K-01. And according to the sample images I found on the web, it is sharp up to there, too, when stopped down to f/8. I think to really get better picture quality, I'd have to go to the Sigma 70-200/2.8 OS or the Pentax 60-250, both of them much more expensive than what I am willing to spend. Off course there is the CA issue with the Tamron, but it is not that big at short and medium length, an I don't need the 300mm. So it doesn't matter if it is weak at 300mm.


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