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05-05-2009, 10:24 AM   #1
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raymeedc's Avatar

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Extension tubes/lens matchup recommendation request

I've just ordered my first set of Pentax auto extension tubes & Copipod. I realize there is, of course, no definitive answer to this question, but which of the following of my SMC M42 Takumar lenses would you recommend as a general walkaround lens to use with one or more of the tubes, & why:
50mm F:4 Macro
50mm F:1.4
55mm F:1.8
85mm F:1.8
105mm F:2.8
I also have a lens reversing adapter ring coming with the tubes.

05-05-2009, 01:01 PM   #2
Lowell Goudge's Avatar

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what do you wish to achieve?

1:1 or something different

typically, the extension tube set you will get is about 50-65 mm of extension.

as a result, it will give a normal 50mm lens 1:1 or a little better, but you will be within 100mm of the subject.

using it on a longer lens will give you less magnification but more working distance.

as an aside, if your SMC tak 105mm is like the SMC Pentax (K mount) 105mm F2.8 I find this lens a little soft wide open,

the 85mm might be a good compromise, not sure about sharpness wide open but it may also be a little soft.

one final point, to get depth of field you need to stop down, but with shorter focal lengths, the apature becomes physically very small and difraction around the openings, percentage wise, becomes important. In this case longer is better.
05-05-2009, 01:37 PM   #3
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The 50mm F:4 macro with a #3 tube will give you 1:1 magnification. Also a true macro lens is always best for copying, as it will be sharp from edge to edge.

It will also be the best choice for reversing.

The 50mm is also the lightest for hand held shooting, but your distance to subject will be short. Especially at 1:1 you will be about an inch from your subject.

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