Board index Photography Technical Questions Has anyone with a tamron 18-270 used a teleconverter

Technical Questions

Has anyone with a tamron 18-270 used a teleconverter

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sharrysas
 
Posts: 1

Has anyone with a tamron 18-270 used a teleconverter

Post Mon Jan 26, 2009 8:19 pm


Hi,
I have checked several 1.4x and 2x teleconverters but from what I can understand they are not recommended for all lenses.
So my question is does anyone on here with a tamron 18-270 lense tried using a teleconverter and if so which one and what are the results like.

dang
 
Posts: 3780

Re: Has anyone with a tamron 18-270 used a teleconverter

Post Mon Jan 26, 2009 11:52 pm


sharrysas wrote:Hi,
I have checked several 1.4x and 2x teleconverters but from what I can understand they are not recommended for all lenses.
So my question is does anyone on here with a tamron 18-270 lense tried using a teleconverter and if so which one and what are the results like.


Teleconverters are recommended for use on lenses of 100mm & above only. There's a few reasons...
1. They're optical properties are tuned toward the longer side, and will probably increase distortions at wide angle.
2. Wide angle lens elements may protrude too far back, and could possibly contact the converter causing damage.
3. The light needed for auto-focus with slower lenses isn't enough, and might cause focus error and possible camera lock up.

Some converters such as Canon, and Sigma are actually quoted as only working with specific lenses of f/2.8 or less.

Hope this helps answer.

moxfactor
 
Posts: 317

Re: Has anyone with a tamron 18-270 used a teleconverter

Post Wed Jan 28, 2009 3:39 am


dang wrote:
Some converters such as Canon, and Sigma are actually quoted as only working with specific lenses of f/2.8 or less.

Hope this helps answer.


about this, it has probably to do with how the teleconverter and the f2.8 lenses are built, because they just don't stick in the right way without glass bumping into each other...

dang
 
Posts: 3780

Re: Has anyone with a tamron 18-270 used a teleconverter

Post Wed Jan 28, 2009 11:07 am


moxfactor wrote:
dang wrote:
Some converters such as Canon, and Sigma are actually quoted as only working with specific lenses of f/2.8 or less.

Hope this helps answer.


about this, it has probably to do with how the teleconverter and the f2.8 lenses are built, because they just don't stick in the right way without glass bumping into each other...

Yes, as stated in "2" above... that's probably correct. Canon (specifically), also say their "contrast detection" requires brighter light to focus properly. So, in this regard, no teleconverter should work with any of their slower lenses. However, a Kenko Pro 300 1.4X does work with many lenses the Canon converter doesn't. It's design doesn't protrude into the lens, but I still wouldn't recommend it with a lens going down to 18mm. Supposing it will fit, the most obvious problem will be vignetting, but distortions can become severe. :wink:


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