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07-25-2012, 10:37 AM   #1
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Teleconverter Help

Hi all,

This is my first post, after quite some time coming to pentaxforums for the excellent posts and reviews.

Here's the thing, not long ago I decided that mechanics are way better than electronics so I parked my DSLR and got a K1000. (Truth be told I still remember my mother's K1000 and how much she regretted selling it).

The K1000 came with the standard Pentax M 50mm f2 lens, which I replaced with the f1.4. Now that I have a fast 50mm I thought about adding a 2x Tele Converter to it. I figured the fast 50mm and the TC would work great. (I have a KX with 28mm f2.8 on the way, so I got the wide lens covered).

However, looking at the Pentax M 100mm 2.8, it really looks like the 50mm+TC will never live up to those standards. Should I forget about the TC and go for the 100mm f2.8 directly? Or will there be no noticeable difference? Speed would be the same, so I guess it is down to image quality. The reason I ask is because a Pentax TC costs about as much as the 100mm from what I've seen, and I don't have enough experience to judge other TC lens brands. (So unless someone points to towards some good, not so pricy TCs for K mounts, budget wise both options are about the same).

Or would it make more sense to get the TC and a 200mm f4? That way I would have 50mm, 100mm (with TC), 200mm and 400mm (with TC). Will the Petax M 200mm f4 with 2x TC be any good? If you had all of the above, based on your experience, what would you end up not using? That's what I'm trying to find out. I'm not indoors focused, so considerations on weight/size will be valuable, though I'm not sure that is much of an argument for getting a TC?

Thanks!

07-25-2012, 10:58 AM   #2
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I think with the prices of good/great lenses in that range being relatively low I would scrap the TC idea, I just don't think it makes sense with wide to normal focal lengths or even short teles . One thing you haven't mentioned is zoom lenses, there are some decent ones out there and then you have one lens that covers a greater range.
07-25-2012, 11:07 AM   #3
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Pentax M 75-150 f/4 quite a remarkable zoom for the time. Quite sharp and constant f/4. Covers the range you would get with a TC and more with likely better IQ than you would get with the TC on the 50mm. Maybe cost $50 - $100 in good shape.

In my experience TC's are not worth the effort until you get over 200mm on the main lens. As littledrawe noted it is not worth it on normal or short tele focal lengths. After 200mm they can be worth it especially if you are trying to avoid getting and carrying a 400mm lens. But understand the image quality will rarely be the same. And then only if the TC is 'matched' to the lens. This is done intentionally by some manufactures to give better IQ and the TC is built with the lens optics considered. For example the Sigma 1.4x and 2.0x APO TC's are matched to certain Sigma lenses.
07-25-2012, 11:27 AM   #4
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I have yet to find a TC that could match up against a well made lens of the same focal length and aperture. I say scrap the TC and go hunt for the M100mm. TC tend to destroy the image quality a lot and even with the best of them it is only marginally better.

07-26-2012, 10:02 AM   #5
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Great. It seems to be unanimous, I'll scrap the TC idea and start looking for a reasonably priced M f2.8 100mm. I think that setup will give me plenty of options to keep me busy. I tend to stay away from Zoom lenses, as the fast ones have a considerably higher price tag, though I guess it won't hurt to at least keep an eye out for them. Though the 2 cameras and 3 primes setup seems reasonable.

Thanks for the responses!!
07-26-2012, 11:23 AM   #6
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With a 2x teleconverter you lose 2 f-stops so the speed would not be the same. This is along with all the other drawbacks raised previously. A teleconverter of 2x or greater in general should be used when there is no other options to get the shot - either you don't have a longer lens with you at the time or can't afford one.

However you might want to look into a Vivitar 2x Macro Focusing Teleconverter. These are optimized for 50mm lenses and can give you 1:1 macro reproduction size. You still have the speed and image quality issues but you can still get good results. These have a semi-cult status so you can end up paying too much for them.

Vivitar 2X Macro-Focusing Teleconvertor Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database
07-28-2012, 07:03 AM   #7
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Hi Not a Number, it is my understanding that if my 50mm is f1.4 and I attach the 2x TC it would be a "100mm f2.8". Is my math wrong? Though I understand this does not necessarily mean the image quality will be the same.
07-28-2012, 04:15 PM   #8
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QuoteOriginally posted by mfenoglio Quote
Hi Not a Number, it is my understanding that if my 50mm is f1.4 and I attach the 2x TC it would be a "100mm f2.8". Is my math wrong? Though I understand this does not necessarily mean the image quality will be the same.
I think your math is right. That means the 200/4 is going to be a 400/8 with the TC, which is going to at least mean a darker viewfinder.

The Vivitar Macro Focusing Teleconverter is actually pretty good. You can save some by looking for the older versions without contacts for A lenses. On a K1000 those contacts are not useful. It's supposed to be optimized for 50mm lenses. If you were thinking of macro work, it might be useful.

Since the K1000 works just fine with M or K lenses, I would buy those first and keep the TC idea for unobtainable/expensive focal lengths. I know a 300mm + TC is not as good as a 600mm, but the cost savings there is huge.

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