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01-01-2013, 12:37 PM   #1
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2x Converter or Lens?

Hi,
Had my Kr for about 6 months now, still a novice getting my way round all the bits and bobs.
I fancy getting more zoomability...
I'm struggling to find info about 2x concerters that wont interfere with auto-focus and so on. Or is that a non-problem?

Can anyone recommend 1 or a good resource for me to read up on them? The lens I have are the twin set that came with the camera markedSMC Pentax Dal 50-200 and 18-55

I saw a second hand Pentax REAR CONVERTER PENTAX 6X7 in my price range will that work for me?

Cheers and apologies if Im being a noob!

Thanks Steve

The photo is one I took over Christmas of the sunset over Newlyn, Cornwall. Obvioulsy I've messed around with it a bit!

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01-01-2013, 01:24 PM   #2
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Welcome to PF!

That teleconverter won't work for you (unless you have a medium format lens - you would know if you do).

Unfortunately there really aren't any great 2x TC's, and the ones that are OK are in the same price range as the Pentax 55-300mm, which in itself is a great lens.

What lenses do you have now? (edit: whoops, saw you have the 50-200).

You're better off with the 55-300. If you want more reach than that, you're looking at $1k on up.

Last edited by ElJamoquio; 01-01-2013 at 01:29 PM.
01-01-2013, 01:25 PM   #3
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QuoteOriginally posted by superduper Quote
I saw a second hand Pentax REAR CONVERTER PENTAX 6X7 in my price range will that work for me?
No.
Pentax has made (and makes) several 'mounts' that are not compatible without adapters. 6x7 and 645 are medium format camera mounts that will only work with cameras that have those mounts. The only current medium format Pentax camera is the 645d which costs about $10,000. There are no current 6x7 cameras but those lenses can be used on k-mount with adapters.

In general using a 2x tele-converter with a consumer zoom (like your 50-200) is an exercise in frustration. You will get the 2x focal length but you also lose 2 stops of light so for the 50-200 @ 200mm you get 400mm f/11 which makes the viewfinder very dark and almost certainly prevents auto-focus from working due to low light levels. And you also suffer image degradation from the additional optics in the TC which often are cheap and un-coated.

Good AF TC's for Pentax are hard to find, although SIgma has both a 1.4x and a 2x. However due to the optics these will only work with some lenses because the rear element projects into the lens and can hit the lens element. These often run over $200usd.

TC's are best used with fast prime lenses with focal lengths over 200mm. You can use them with any lens but the results are seldom good. Most people who have done testing report that simply cropping the image results in a better image than using a 2x TC. Fast primes being the exception.

If you want a bit more zoom may I suggest you take a look at the DA L 55-300. You can likely get one for not a whole lot more than a good AF TC and you will be much happier in the long run.
01-01-2013, 01:58 PM   #4
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Converters don't work for me.The 55-300 is a good choice.If buying used look at the FA 100-300 f4.7.

01-01-2013, 02:57 PM   #5
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I tried a 1.5x teleconverter (Kenco) and was disappointed with the results. As said above, you lose too much image quality and stops of light for my liking. They generally seem to be a bit of a compromise. I sold it and put the proceeds towards a better lens.
I agree with 'ElJamoquio' that the 55-300 lens would be a better solution. Sell your 50-200 and add the money you would have spent on a teleconverter to get the 55-300, and it will do a much better job for you.
01-01-2013, 03:57 PM   #6
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I cannot address the AF question, however, using 4 off brand 2x teleconverters (TC) [for nikon and pentax m42, and pentax K), if used with top quality lens (e.g., Nikon 55mm f2.5, Pentax M 50mm f1.7, K 135 mm f2.5] I found all of the results satisfactory. And excellent for macro.

This is consistent with experience of some excellent (but dated) authors (Blaker and Lefkowitz). Of course another top quality longer lens should be be better but it's likely not in your kit, doesn't focus close enough, is huge, etc.

But I have hardly used them with digital. When backpacking my kit is 1-2 film camera and a moderate wide angle (35mm) and a 50-55mm macro, and a 2x TC.

Basically I would assume most zooms (unless superb) would not be a good idea. I have never tried it with zoom--but I don't consider zooms except where the fast pace and need to zoom are important, and under those condition the teleconverter is pointless anyway.

It partly depends what you want it for--and the expectations you have. I suggest you simply buy one (for $10-$50) and try it with a good prime lens.
01-02-2013, 06:19 AM   #7
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There are only two reasons in my opinion for using a teleconverter; space, and budget.

Budget is the easy one to understand; while teleconverters are almost always less expensive than a comparable telephoto lens, the image quality is also almost always less. Further, depending on the subject and its lighting, and the intended use of the image, you might be just as well off cropping your image (also known as 'digital zoom').

The other reason is space ... even if you can afford the super-humongous telephoto lens, it may be too big or heavy for you to transport under some circumstances. Teleconverters are generally smaller and lighter than packing another full lens - especially a telephoto lens. Still, due to the image degradation, cropping may be a better option.
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