Author Topic: Totaly confused about TC's  (Read 2045 times)

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Offline a350novice

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Totaly confused about TC's
« on: July 15, 2008, 01:01:07 AM »
This is what I have.
Sony Alpha DSLR-A350 Camera Body
50mm f/1.4 lens - Rare crossed X's
Sony DT 18-70mm f3.5 Zoom lens
Sony 75-300mm f/4.5-5.6 for Alpha
Sigma APO 70-300mm F4.5-5.6

Question is: I purchased a Sakar 1.4 M/AF teleconverter. When I got it I tried it on all the above lens. The only lens that would auto focus was the 50mm f1.4. I tried reading the info at
http://www.dyxum.com/lenses/TC/index.asp from your board, but still not sure what it all means.
Is there a Teleconverter that will work with any zoom lens?
Thanks

Offline fother

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Re: Totaly confused about TC's
« Reply #1 on: July 15, 2008, 01:08:58 AM »

The AF system requires a minimum aperture of F6.3 to function, if the lens (with teleconverter) goes beyond f6.3, it's manual focus only.

A 1.4x Teleconverter adds one stop to the lens.

The 75-300 will be manual focus only, and I suspect the 18-70 will too.

However, teleconverters really shouldn't be used for focal lengths below 50mm (they're just not suitable - too many compromises, you'll get big distortions), so the 18-70 is also not suitable for teleconverter use at all, let alone autofocus.

Offline a350novice

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Re: Totaly confused about TC's
« Reply #2 on: July 15, 2008, 01:23:55 AM »
Thanks Fother.
I think I will forget about TC's. I have a lot of older stuff I am going to sell and narrow down my Lens. I will for sure keep the 50mm. I just ordered the Sony SAL-70300G 70-300mm f4.5-5.6 Super Telephoto Lens from Circuit City for $799.00 plus tax. It is a lot of money but from what I have been reading on this forum I will be better off getting a few good lens than a lot of not so good ones.

Offline fother

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Re: Totaly confused about TC's
« Reply #3 on: July 15, 2008, 01:27:24 AM »


Always happy to help :)

I will be better off getting a few good lens than a lot of not so good ones.

I agree completely :)