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 Post subject: 2X teleconverters
PostPosted: Sat Dec 08, 2007 12:03 am 
If you mount a 2X teleconverter does it automatically set your aperture to like f/8? Because if not couldn't I get one and mount it with my 50mm f/1.8 to make it a 100mm(150mm) f/1.8 with a minimum focusing distance of like 10in. would it make a good macro lens?


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 Post subject:
PostPosted: Sat Dec 08, 2007 12:22 am 
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Hi Nathan,

Check out this definition of f-number. If you double the effective focal length of a lens with a teleconverter then the best f-number also doubles (to 3.6 in your example). :cry:

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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 Post subject:
PostPosted: Sat Dec 08, 2007 1:20 am 
Oh, well still I think I would be able to get some good macro @ 100mm f/3.6 from like 10in. away.


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 Post subject:
PostPosted: Sat Dec 08, 2007 8:23 am 
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With every tele-converter the closest distance to the subject remains as with the original lens, only the manification is increased 2x (with a 2x converter that is).
So as your 50mm gets down to approx. 1:8 you'll be able to do 1:4 with a 2x converter - nothing more...
And beware:
1. You need a good converter
2. The optical resolution of every lens is reduced by 2
The latter may no pose a prob if the lens is very good and exceeds the sensor-resolution. But in some cases you may be equally well off to do digital-zooming in with pp.

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Thomas (beware: Nikon-fanboy and moderator!) My Lens Reviews, My Pictures, My Photography Blog
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 Post subject:
PostPosted: Sat Dec 08, 2007 4:27 pm 
Thanks guys I was just curious. I don't plan on picking one up any time soon or ever but I just wanted to about them. Thanks again.


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 Post subject:
PostPosted: Tue Dec 18, 2007 12:04 pm 
I think teleconverters can be used well for astro-photography... Just check Gordons video regarding this topic: http://www.youtube.com/watch?v=lxTalp6f7kw


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