Author Topic: Teleconverters - use of?  (Read 2629 times)

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Offline Frank [aka Wires]

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Teleconverters - use of?
« on: February 13, 2016, 11:35:26 PM »
Feeling that the NEWS topic of the new FE f2.8 glass was beginning to slide off topic (MY fault I feel) with going on to teleconverters I thought of starting a new topic on the use of them as I'd been under the impression they changed the f stop of a lens by X amount as well as the focal length depending on the converter used: 1.4X or 2X

Charles (Ascot) mentioned in a reply to my posting that they only extend the focal length not the aperture so I went off to try and find some information as I'd always been under the impression as mentioned above and in a reply posted in the New FE Glass topic. I came across this web page and give the link (unshortened - sorry) and a part quote from the "Cons" section:

http://digital-photography-school.com/the-pros-and-cons-of-using-tele-converters-extenders-on-your-dslr/ by Darren Rowse:

Quote: "Lens Speed – The first thing to consider when using a teleconverter is the impact it has upon how much light gets into your camera.

Using teleconverters means less light gets in which means your maximum aperture will be decreased. When using a 1.4x converter this means you’ll lose one stop and when using a 2x converter you’ll lose two stops (It was for this reason that I went for a 1.4x teleconverter instead of the 2x one as I didn’t want to slow my lens down any further than f/5.6).

So last year at the tennis, instead of being able to shoot at f/4 with my camera I had a maximum aperture of f/5.6. ..."


and so it continues further with other 'cons'...

So... this is why I've been under that impression about the aperture. I'd appreciate more input on this topic as I've never used a teleconverter myself, don't have any for the glass I have so am unable to do any testing (?) that would show the true effect, if any, on the aperture of a lens when used; does it show in the exif? - is it noticable in any other way?
Frank (aka Wires)
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Offline chappo1

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Re: Teleconverters - use of?
« Reply #1 on: February 13, 2016, 11:39:10 PM »
Correct Frank
A 1.4 teleconvertor (I have one) reduces the maximum F stop by 1.
A 2 x reduces it by 2 stops.

john
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Offline AScot

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Re: Teleconverters - use of?
« Reply #2 on: February 14, 2016, 04:30:08 AM »
Frank, you are totally correct. My statement that "the teleconvertors only increase the focal length, they do not change the aperture" is wrong. As John states A 1.4 teleconvertor reduces the maximum F stop by 1. A 2 x reduces it by 2 stops. I have a long boring reason for stating what I did but I will not embarrass myself or you any further by revealing it. I will just say I am very sorry.
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Offline Frank [aka Wires]

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Re: Teleconverters - use of?
« Reply #3 on: February 14, 2016, 07:40:39 AM »
I am the one to apologise to you Charles and do so now- unreservedly: I am very sorry indeed.

There is absolutely NO reason to apologise for what you mentiond Charles - absolutely none at all.

If anyone should be apologising then it is me for embarrassing you. That certainly was not my intention to do that. So please accept my apologies for doing so.
Frank (aka Wires)
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Offline REX (aka TG)

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Re: Teleconverters - use of?
« Reply #4 on: February 14, 2016, 02:55:25 PM »
Timeout!

You (all) have not to apologise we are all here to help each other. We are human and mistakes are in our life.

I personally use 1.4x and 2.0x regularly on 300G and I am very pleased. When I don't need to use it I just remove it and have a lens that work from f2.8.

Using the converters you have to close aperture one or two stops to get reasonable results for example 300G f2.8 with 2.0X you have f5.6 so if available light is enough then f8.0 will give the best results
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Offline Sarg

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Re: Teleconverters - use of?
« Reply #5 on: February 15, 2016, 04:29:29 AM »
One other issue with TC's is loss of image quality. The matched TC's have less distortion than the generic ones but there is a noticeable degradation. I currently have the Minolta 1.4 and 2X TC's and the Tamron 1.4 and 2X TC's. I did have the Sigma's as well. Why so many? The Tamron's are generic and will fit all lenses while the Minolta and Sony only fit selective G lenses. For instance I can use the Minolta on the 70-400G but not on the Tamron 150-600.
One handy feature is, I have the Samyang 8mm fish-eye which is good on the A77II but not so good on the A99 but add the 1.4x TC and it works on the A99.