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04-09-2010, 09:44 PM   #1
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Teleplus

Hello all, I have ( with 2 pentax cameras that I purchased second hand) a 2x APK Macro Teleplus Mc7 lens. Can anyone please tell me what it is for/does
thankyou
Shaun

04-09-2010, 10:04 PM   #2
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QuoteOriginally posted by Hermosil Quote
Hello all, I have ( with 2 pentax cameras that I purchased second hand) a 2x APK Macro Teleplus Mc7 lens. Can anyone please tell me what it is for/does
thankyou
Shaun
Not familiar with Teleplus brand name (or type) but it sounds like a Macro Focusing 2x Teleconverter. Basically it doubles your lens focal length by putting a lens on it and mounting the whole contraption to your camera. Thus, a 50mm lens will become a 100mm lens in effect. It also half's the lens speed. If that 50mm is an f2.0 the resulting lens will be a 100mm f4. Macro focusing means that you can use the combo to do Macros. The Vivitar version of this unit will do 1:1 (life size) with a 50mm lens. PKA means that the converter has a contact or contacts to transmit lens aperture info to the camera so that you can do Aperture priority with an appropriate lens without messing with the aperture ring.

To gain a better idea,

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/27163-vivitar-...ve-thread.html

04-10-2010, 12:58 AM   #3
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QuoteOriginally posted by JeffJS Quote
It also half's the lens speed. If that 50mm is an f2.0 the resulting lens will be a 100mm f4.
Slight correction: It cuts the speed by 3/4, not by 1/2. That's 2 f-stops.

Half of f/2 is f/2.8. Half of f/2.8 is f/4. Only 1/4 of the light gets through.

So Shaun, if you used that 50mm f/2 lens wide open, and got a meter reading for a shutter speed of 1/100 sec, and then added the the teleconvertor, the new shutter speed would be 1/25 sec. Read up on exposure to see how f-stops and shutter speeds are related. Have fun!
04-10-2010, 01:08 AM   #4
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QuoteOriginally posted by RioRico Quote
Slight correction: It cuts the speed by 3/4, not by 1/2. That's 2 f-stops.

Half of f/2 is f/2.8. Half of f/2.8 is f/4. Only 1/4 of the light gets through.

So Shaun, if you used that 50mm f/2 lens wide open, and got a meter reading for a shutter speed of 1/100 sec, and then added the the teleconvertor, the new shutter speed would be 1/25 sec. Read up on exposure to see how f-stops and shutter speeds are related. Have fun!

Thanks for the correction.



04-10-2010, 09:24 PM   #5
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Thankyou for your answers.1 quick question I mounted the converter on my P30 t with the70- 300 Zoom lens, which do you focus first , the converter or the zoom lens. also can I use both the converter and the lens on my Sfxn also?
Thankyou
04-10-2010, 09:47 PM   #6
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I'm assuming that yours is like the Vivitar.. If you want to use it as a straight 2x converter, set the converter focus ring to Infinity and then focus your lens. For anything else, select the magnification ratio on the converter and then focus the lens. Keep in mind that those ratios are intended for a 50mm lens and are not necassarily what you'll get when using a 70-300 zoom. Don't be afraid to experiment.

04-13-2010, 08:52 AM   #7
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QuoteOriginally posted by JeffJS Quote
I'm assuming that yours is like the Vivitar.. If you want to use it as a straight 2x converter, set the converter focus ring to Infinity and then focus your lens. For anything else, select the magnification ratio on the converter and then focus the lens. Keep in mind that those ratios are intended for a 50mm lens and are not necassarily what you'll get when using a 70-300 zoom. Don't be afraid to experiment.

This is good to know as I have never also used one of these and am curious why at times it brings up a high price off ebay..specially those ones with the electrical contacts.
I always see these Vivitars but never knew how to use them, so I never bothered to bid for them.
It would seem that they function like the Pentax AF 1.7X TC then, it is just that the Pentax TC is AF.
04-13-2010, 10:18 PM   #8
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Thankyou

Thankyou for all your replies looks like I have some experimenting to do.
Can anyone tell me what to look for in joining a camera club and is there any in Adelaide South Australia that I could join.
Thankyou

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