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09-19-2011, 01:08 AM   #1
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telconverter

Q dose anyone use one if so which one and much as im looking to get one

09-19-2011, 03:09 AM   #2
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Good TC's are expensive.
Cheap TC's are not good.

Unless you use a high-end TC, preferably with a matched long lens, you will get better image quality by just cropping and enlarging your pictures.
09-19-2011, 05:13 AM   #3
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even a cheap teleconverter beats cropping as long as you've got a decent lens and can get away with using a slower shutter speed.
09-19-2011, 05:31 AM   #4
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you need to be a little more specific about what you wish to achieve with a Teleconverter first.

There are some very very good specific use TCs.

- sigma TCs are exceptionally good, but intended for use on specific sigma LONG and FAST tele zooms and primes. THey do not fit all lenses due to the front element projecting into the rear of the main lens. the lens needs the rear element recessed at leastr 12mm and the recessed opening nees to be 35mm in diameter. The sigma TCs DO NOT support HSM, and do not modify any of the native lens data passed through to the camera so EXIF data is not corrected, but more importantly, focal length for shake reduction is not corrrected, nor is the true aperture, causing both exposure errors on some bodies and the need to compensate exposure for P-TTL flash
- pentax makes similar (to sigma) but more extreme rear converters, for some older lenses
- pentax makes a very good and versitile 1.7x converter which also includes an auto focusing element, ment to convert old MF lenses to AF. it is very good, has A contacts, so a KA mount lens will have all exposure modes functionning. the TC also corrects the aperture so true aperture is recorded, making metering and P-TTL flash metering accurate on all cameras.
- tamron and kenko make reasonably good general purpose TCs and there are some models with power contacts origonally used for the pentax Power zoom film cameras, which have some compatibility reported for HSM.

anything else is relitive junk, in my opinion

09-19-2011, 06:30 AM   #5
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I think Lowell just about nailed it.
09-19-2011, 11:13 AM   #6
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im looking to use it on with my 70-300 and 18-200 for sport (track days and also wildlife also ? can the distance TC be used for macro
09-19-2011, 05:53 PM   #7
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this is a link to kenko and tamron teleconverter with pictures.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/19694-tamron-t...rter-pics.html
09-19-2011, 06:23 PM   #8
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QuoteOriginally posted by Rusky40 Quote
im looking to use it on with my 70-300 and 18-200 for sport (track days and also wildlife also ? can the distance TC be used for macro
then I am afraid you will be out of luck

One thing I forgot to mention in my post is that for AF to function, ou will need a combined aperture faster than F6.7, that means the native lens aperture for a 1.4x TC must be F4.5 or faster, for a 1.7x TC F4 or faster and for a 2x TX F3.5 or faster.

If your lens does not meet these speeds, your camera's AF simply won't work.

on consumer zooms, the addition of a TC generally degrades the image more than cropping in, unless you are so far away that the pixel resolution is the limiting factor. (that is a long way away)

09-19-2011, 06:41 PM   #9
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In my view, the loss of AF is not a huge problem: manual focus is really not all that difficult.

This
QuoteOriginally posted by Lowell Goudge Quote
on consumer zooms, the addition of a TC generally degrades the image more than cropping in, unless you are so far away that the pixel resolution is the limiting factor. (that is a long way away)
is much more significant. For better-than-cropping results, both the lens and TC must be very high-quality.
09-19-2011, 07:57 PM   #10
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QuoteOriginally posted by maltfalc Quote
even a cheap teleconverter beats cropping as long as you've got a decent lens and can get away with using a slower shutter speed.
Must disagree strongly here. Any TC will magnify a lens' problems, and a bad TC will magnify them badly. Yes, there are times when cheap TCs are appropriate, like for surveillance, blackmail, where stark content is more important than photographic quality -- where a crappy photo is better than no photo at all. But using cheap TC's on less-than-suberb lenses pretty much guarantees crappier photos than cropping will produce.
09-19-2011, 08:45 PM   #11
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There can be... only one....... Pentax- F 1.7x AFA which i manged to get my sweaty hands on just last week

I took this on Sunday with DA 55-300 and AFA 1.7x, wide open (f8), handheld at (almost) 500mm. Subject was around 200meters away. (Generally this is not a recommended combination, but in the absence of a 300/4, what the hey)

Very bright condtions around EV15 and used autofocus on the AFA which is very short quick.
If the light wasnt so good the AF would be very hit & miss, like my skills of compostion


I found the image is often affected by heat haze many times worse than optical defects. I have a shot of a superyacht from 4000m and it looks horrible, even across water. In this case the shorter distance and the 20kts of breeze help to neutralise this.
09-20-2011, 02:07 PM   #12
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cheers guys so cheep is not good then or a M42 with a K converter

Last edited by Rusky40; 09-20-2011 at 02:17 PM.
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