Camera Labs

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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Canon EOS 5D + 50mm f/1.8

http://flickr.com/photos/nathan_ward

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).

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.

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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Canon EOS 5D + 50mm f/1.8

http://flickr.com/photos/nathan_ward

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
D800+assorted lenses

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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Canon EOS 5D + 50mm f/1.8

http://flickr.com/photos/nathan_ward

I think teleconverters can be used well for astro-photography... Just check Gordons video regarding this topic: http://www.youtube.com/watch?v=lxTalp6f7kw