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Old Sep 18, 2010, 7:17 PM   #1
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Default Extender Question

Let's say I'm using a 2x extender, so I'm turning a 100mm lens into a 200mm lens.

I know that I'll lose one or two fstops. But what about the effect on the sharpness of the lens?

What are common effects on the I should look for when using an extender?

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Old Sep 18, 2010, 9:19 PM   #2
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Any time you add optical elements to the light path, image quality suffers. This has been mentioned on multiple occasions everytime someone mentions using filters. The same is true with extenders/teleconverters, except that they are much more complex and prone to flaws. Some teleconverters are better than others. In general, like filters, the best indication of optical quality is price. But you need to be aware than the more expensive teleconverters are "Matched", meaning that they only work with a few lenses; using a Matched teleconverter with a lens that it was not intended to be used with can damage the lens and/or the teleconverter.

The effects of using a teleconverter (beyond just the change in focal length and f number) are a loss of sharpness and an increase in chromatic aberration.

And, fyi, a 1.4X teleconverter adds 1 f-stop to the maximum aperture of a lens, and a 2X teleconverter adds 2 f-stops.
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Last edited by TCav; Sep 19, 2010 at 2:24 AM. Reason: added effects
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Old Nov 30, 2010, 7:20 PM   #3
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Quote:
Originally Posted by TCav View Post
The effects of using a teleconverter (beyond just the change in focal length and f number) are a loss of sharpness and an increase in chromatic aberration.

And, fyi, a 1.4X teleconverter adds 1 f-stop to the maximum aperture of a lens, and a 2X teleconverter adds 2 f-stops.
Would a 2.2x teleconverter be almost worthless on an overcast day or could you increase ISO ? I often shoot distant wildlife and sometimes a mediocre photo is better than none.
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Old Nov 30, 2010, 7:41 PM   #4
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There are many things you could do (increasing ISO is one) to "Get the Shot" but
whether or not it's acceptable is up to the person taking the shot...

Here'a a little info that may help...

http://www.digiscoped.com/teleconverters.html

Bottom line ~ The better, sharper, faster the lens you're working with the better
your results will be, ie; you'll loose less with an expensive, sharp, f2.8 lens than
you would with a cheap, soft, f6.3, but you will loose something no matter what
lens or converter you use... Acceptable is up to you...
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Old Nov 30, 2010, 8:10 PM   #5
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Thank you for the link and reply. Much appreciated !
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Old Nov 30, 2010, 9:13 PM   #6
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Quote:
Originally Posted by Logo10heli View Post
Thank you for the link and reply. Much appreciated !
You're welcome, and good luck...!

Last edited by Wizzard0003; Nov 30, 2010 at 9:41 PM.
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