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12-23-2010, 01:39 PM   #1
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Any one with experience with Tele-Converters?

Hello...

I am new to DSLR world and I have a Kx with a Tarmon 18-200mm and a 70mm-300mm lens. I am looking for a Tele-Converter to enhance the range of these lens. I have searched the forms and didn't come up with the answers I am looking for. I hope someone can share some experiences or answers with me.

Have any one used any one of these companies for a Tele-Converter, Pro-Optic 2XPX or Bower MC7 or MC4?

Does the number of elements means better picture? 4 Elements vs 7 Elements?

If paired with the config I have now a K-x with Tamron 18-200mm or Tamron f4 -5.6 70-300 lens would the AF still work?

Thanks any help would be great.

12-23-2010, 01:59 PM   #2
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7 elements 2X TC should perform better in theory, but the actual quality varies. However, it won't be practical with 200-300mm f5.6 lens which is not sharp to start with. AF won't work and the viewfinder will be very dim. You don't get something for nothing I am afraid.
12-23-2010, 04:08 PM   #3
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Most comments I have read say the 7 element TC's are better than the 4 element.

Not all TC's are the same by any means. Many do not pass through the lens information or have the pass through for auto-focus.

Here is one that says it does auto-focus but I would be very careful.

Loss of light is always going to be a problem as well as the loss of some sharpness. Sometimes getting any picture is better than not so the sharpness issue can be OK in some situations. The light loss, maybe 2 stops, depending on the converter might be a deal breaker for your lens combination. Those are not really fast to start with. But if you are working in bright sunlight it might not be too bad.

Here is a quote from the Bower MC7 literature "AF will be retained with the 2X teleconverter if the master lens is F/4.0 or faster. If the aperture is slower, the in-focus lights will work but focusing must be done manually."

The problem is even if the TC has the auto-focus connections your lens must be at least f4 for enough light to pass through for reliable auto-focus.


12-24-2010, 09:16 AM   #4
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Thank for the replies....

I will be taking pictures in the day light.. So, I hope that should work... I know my lens are not the best and sharpest out there... but I am hoping to get any pictures..

So, If my lens is an f4 lens... in theory the auto focus would work?

12-24-2010, 09:40 AM   #5
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Actually your lenses are rated fairly good in the lens database, but they are fairly slow. That is not unusual for zooms of this quality and cost. Fast long zooms are very, very expensive.

The problem I see is that your lenses vary in maximum aperture over the range of zoomed focal length. At the wide end (I think one is f3.5 and the other is f4) they should work. However at the telephoto end they are f6.3 and f5.6 which means you will possibly have problems with the auto-focus. So at the long end where you are most likely to use a TC is where you will have the most problems.

All that said, you won't really know until you try it under the conditions you are shooting under. I use a TC quite often but only on my manual focus prime telephotos so I have never had to worry about the auto-focus issue.

Also keep in mind you will need a sturdy tripod and a remote release especially with the 70-300. With the TC that gives you a 600mm lens and you will not be able to hand hold it.

I have used my S-M-C Takumar 400mm on a tripod along the interstate and got lots of blur caused by the wind of passing trucks. That is enough to move the lens.
12-24-2010, 10:12 AM   #6
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from my experience, at the telephoto end of the focal length range, you will be exceedingly lucky even in bright daylight to have AF function with anything resembling reliability, when using a TC.

Regardless of image quality issues, you will be manually focusing and will be doing so without the benefit of focus confirmation.

Personally, I would not recommend it
12-26-2010, 06:36 AM   #7
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I am so new to DSLR you should discount what I say but I have used an older PK/A 2X converter with an older 200MM telephoto and a 135 that I have. In decent daylight, manual mode, manual focus they took acceptable pictures.
12-26-2010, 07:47 AM   #8
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QuoteOriginally posted by itzmechih Quote
Thank for the replies....

I will be taking pictures in the day light.. So, I hope that should work... I know my lens are not the best and sharpest out there... but I am hoping to get any pictures..

So, If my lens is an f4 lens... in theory the auto focus would work?
You probably wouldn't loose any more image quality by cropping images instead of using tele-converters. Especially when using TC on low budget lenses.

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