Tele-Converter


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tyonghen

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Jan 22, 2008
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#1
Hi, read the article that Kenko 2x tele-converter needs f2.8 and higher. Does that means that it cannot be used for lens of f3.5-f4.0 type? Thinking of getting one to increase my zoom but my lens fall within range of f3.5-f4.0.
What will be the effect or consequences if use AF?

Lost and confuse

:confused: :eek:
 

satan_18349

Deregistered
May 6, 2004
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hell 極樂世&
#2
Hi, read the article that Kenko 2x tele-converter needs f2.8 and higher. Does that means that it cannot be used for lens of f3.5-f4.0 type? Thinking of getting one to increase my zoom but my lens fall within range of f3.5-f4.0.
What will be the effect or consequences if use AF?

Lost and confuse

:confused: :eek:
2x converter will render your lens not able to AF and pics quality drop drastically.. Ideal is a 1.4x or better still, walk closer.
 

yannh

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Dec 10, 2007
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Woodlands
#3
As I know, 2x tele-converter will make you lost 2 stops of lights, as if 2 stops aperture smaller. So F4 will become like F8, and AF camera will lost the ability to focus at that point. So it is usually advisable to use F2.8 or lower lens.
 

andrewtansj

Senior Member
Jul 26, 2007
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#4
best to get a 1.4X tele converter... less IQ degrade... I have both 2X and 1.4X, seldom use 2X as as AF don't seem to work as well and image obviously softer.
 

Stress

Senior Member
Sep 5, 2006
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#5
Hi
It will work just that it maybe slow. IQ not that good but if you are not blowing it up and print 4R or max 8R should not be an issue. AF will work but may hunt is it's dim.
Hi, read the article that Kenko 2x tele-converter needs f2.8 and higher. Does that means that it cannot be used for lens of f3.5-f4.0 type? Thinking of getting one to increase my zoom but my lens fall within range of f3.5-f4.0.
What will be the effect or consequences if use AF?

Lost and confuse

:confused: :eek:
 

slooow

New Member
Feb 12, 2006
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#6
AF will become super slow and almost 99.99% inaccurate

hehe

but for a newbie like me, i still find it fun

Moon taken with a cheap 70-300 lens... aperture F5.6 + kenko teleplus pro 300 dg 2x

hence i think the aperture became f/11.2? hehe

 

undergrd

Senior Member
Jun 16, 2007
1,984
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#7
AF will become super slow and almost 99.99% inaccurate

hehe

but for a newbie like me, i still find it fun

Moon taken with a cheap 70-300 lens... aperture F5.6 + kenko teleplus pro 300 dg 2x

hence i think the aperture became f/11.2? hehe

cant see ur pic...but how is the quality of the pic??
 

giantcanopy

Senior Member
Feb 11, 2007
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#8
Good shot. The sky must be pretty clear!

There is some visible chromatic noise exacerbated by the cropping that can be controlled with abit of noise removal.

Ryan
 

giantcanopy

Senior Member
Feb 11, 2007
6,232
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#9
cons of getting a teleconverter :

Max aperture of ur lens drops by the factor of the teleconverter u use.
A handholdable lens will at the same settings might not be after adding a teleconverter.
( not to mention the longer focal length magnifying any hand movements )

Focusing speed decreases as a result of the smaller aperture / lower light entering the cam sensor. When it drops past a certain limit ( e.g smaller than 5.6 ) Focusing starts to hunt and becomes unreliable.

Image quality drops. Any exising flaw of the lens is magnified by the teleconverter ( compounded by whatever flaws the teleconverter has ) The longer the teleconverter, the more prone to image degradation. A 1.4x is good but many a times the reach u get is not alot either.
 

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