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05-22-2011, 10:08 PM   #1
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Best K Mount 2x Teleconverter?

I want one with the best optics regardless whether it has Pentax-A and on up support--manual aperture is fine (if it has better optics).

Thanks!

05-23-2011, 08:43 AM   #2
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If it's for digital, I will bet none you can find will do than simply cropping. But it's certainly possible there might be an exception if paired with the right lens.
05-23-2011, 02:16 PM   #3
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TCs are a crap shoot. You might find one that works well with a lens you have, but not so good with a different lens. Some Sigma TCs will only mount on certain lenses. Other TCs will only work in manual mode. You have to be careful when shopping and know what you are buying.
05-23-2011, 02:29 PM   #4
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QuoteOriginally posted by geekette Quote
I want one with the best optics regardless whether it has Pentax-A and on up support--manual aperture is fine (if it has better optics).

Thanks!
That's not an easy task. If you have lenses, that will accomodate the long protruding front element, I think, that the Pentax A 2x-L is the best 2x tc. But it fits only a few lenses. Otherwise the Pentax A 2x-S is another choice, but quality loss will be detectable.
On some lenses, the old Kenko MC7 (A version) is indeed a very good performer (on the K 300/4 for instance), on other lenses, it is mediocre.
If you have one of those Sigma zooms, which will match with the Sigma Apo tcs, then that would be the preferred choice.
Also, if you can forego the full 2x factor, the Pentax 1.7x AF-adaptor would be an interesting and versatile option, with very good image quality.

Ben

05-23-2011, 03:53 PM   #5
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QuoteOriginally posted by Ben_Edict Quote
That's not an easy task. If you have lenses, that will accomodate the long protruding front element, I think, that the Pentax A 2x-L is the best 2x tc. But it fits only a few lenses. Otherwise the Pentax A 2x-S is another choice, but quality loss will be detectable.
On some lenses, the old Kenko MC7 (A version) is indeed a very good performer (on the K 300/4 for instance), on other lenses, it is mediocre.
If you have one of those Sigma zooms, which will match with the Sigma Apo tcs, then that would be the preferred choice.
Also, if you can forego the full 2x factor, the Pentax 1.7x AF-adaptor would be an interesting and versatile option, with very good image quality.

Ben
The 1.7x sounds fine, since it has good image quality; but how is it with compatibility? Say M42 lenses (with adapter), Pentax-M, Pentax K and Pentax-A lenses

Regarding the Pentax A 2x, would that work with a Tokina M42 400mm 6.3 lens? I'd like to have 800mm and point it at the moon, jupiter, saturn etc.. Kinda use it as a telescope.
05-23-2011, 04:13 PM   #6
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The 1.7 AF convertor is a wonderful piece of kit! With an A lens, it turns it into a fully automatic AF lens. Not only that but it also works very well for macro because not only do you get the focus range with the AF convertor which you wouldn't with a normal 2x one but you can add that to the lenses own range.

It also works well with K and M lenses but doesn't seem to like to autofocus with M42 lens in an adapter although you can still manually focus them.

Kim

QuoteOriginally posted by geekette Quote
The 1.7x sounds fine, since it has good image quality; but how is it with compatibility? Say M42 lenses (with adapter), Pentax-M, Pentax K and Pentax-A lenses

Regarding the Pentax A 2x, would that work with a Tokina M42 400mm 6.3 lens? I'd like to have 800mm and point it at the moon, jupiter, saturn etc.. Kinda use it as a telescope.
05-23-2011, 04:23 PM   #7
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QuoteOriginally posted by Kim C Quote
It also works well with K and M lenses but doesn't seem to like to autofocus with M42 lens in an adapter although you can still manually focus them.
It will autofocus with m42 lenses if you short the contacts on the lens side of the AF 1.7x adapter with a piece of aluminium foil or aluminium tape. Same for K and M series lenses.

With all lenses, M42, K, M or A, you will need to pre-focus the lens manually to approximate focus, before the AF1.7x will focus, as the focus range is short.
05-23-2011, 04:33 PM   #8
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I tried it with a "K" lens and it worked without shorting it. I must admit, I don't really intend to use it with any M42's. I Have a "good" selection of the K range of lenses and I don't have anything in M42 which isn't covered.

I tend to use it most with the longer A series lenses. 100/2.8, 135/2.8, 200/2.8 and 300/4.

Kim

QuoteOriginally posted by selar Quote
It will autofocus with m42 lenses if you short the contacts on the lens side of the AF 1.7x adapter with a piece of aluminium foil or aluminium tape. Same for K and M series lenses.

With all lenses, M42, K, M or A, you will need to pre-focus the lens manually to approximate focus, before the AF1.7x will focus, as the focus range is short.


05-23-2011, 04:48 PM   #9
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The 1.7x adapter works quite well with all the lenses I have... including the DA*300.



http://farm5.static.flickr.com/4090/5115810377_91a53619ea_o.jpg

but they cost $350+.. It might be best to define exactly (as close as possible) what you want to do, aside from just doubling the lens. Remember that with a 2x you also cut the light in half reaching the sensor so with a 'slow' lens, it may require some quite long shutter times or force you to shoot wide open.

Here is a photo with the FA43 mounted on a Vivitar 2x Macro Focusing converter.



It doesn't make a great long distance converter with all lenses however. That's why I say, it's important for you to define what you want to do with it.

For a moon shot, you might do better to get a telescopic lens.

Taken with a Vivitar 600-1000




Last edited by JeffJS; 05-23-2011 at 04:54 PM.
05-23-2011, 05:51 PM   #10
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AF 1.7x can produce some interesting bokeh when paired with certain lenses, in this case, a Vivitar Series 1 105 Macro:

05-23-2011, 06:00 PM   #11
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I love it! But wow that little sucker is so expensive lol. I am not used to paying more than $100 for lenses yet lol.
05-23-2011, 06:04 PM   #12
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QuoteOriginally posted by geekette Quote
But wow that little sucker is so expensive lol.
You asked for the best.
05-23-2011, 06:37 PM   #13
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QuoteOriginally posted by JeffJS Quote

but they cost $350+..
That must be why the person who bought mine in the Marketplace for $275 said it restored their faith in humanity that there was someone willing to sell it at a reasonable price. LOL (I only paid $300, and thought $275 was pretty good)
05-23-2011, 06:46 PM   #14
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I'm speaking in terms of typical ebay auctions. The most expensive I ever saw one actually sell for was over $500. I've seen buy it nows from asian sellers at over $600 though I doubt anyone will pay that. The last one I watched went for $375 or within change of that. It's one of those things that if you're willing to pay a going rate, you really can't spend much time worrying about the price (within reason of course). I think I gave $340 for mine shipped from Australia on the marketplace. The combo of that and the 300 are just as good if not better than the Bigma they replaced (already had the DA*300). 510mm at seemingly half the weight.

05-23-2011, 06:54 PM   #15
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QuoteOriginally posted by JeffJS Quote
I'm speaking in terms of typical ebay auctions. The most expensive I ever saw one actually sell for was over $500. I've seen buy it nows from asian sellers at over $600 though I doubt anyone will pay that. The last one I watched went for $375 or within change of that. It's one of those things that if you're willing to pay a going rate, you really can't spend much time worrying about the price (within reason of course). I think I gave $340 for mine shipped from Australia on the marketplace. The combo of that and the 300 are just as good if not better than the Bigma they replaced (already had the DA*300). 510mm at seemingly half the weight.

I keep thinking about the 300 f4. Makes a 510 ~f5.8, yes?

Then I see the old Tamron SP 300mm f2.8 on eekbay for $500 and go hrm... (I have the SP 2x and the SP 1.4x, along with the SP 180mm f2.5). I used to rent that lens and got some stunning images with it...

EDIT: So I went and looked on ebay for the 300 2.8 or the 400 f4 (tamron SP) and there's a 30a (the old 80-210 f2.8 SP Adaptall... interesting).
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