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11-26-2009, 07:49 PM   #1
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Macro confusion.......

Hi,

I am confused a little. In order to be able to achieve a 1:1 size using extension tubes on my K20:

1) Do I have to use a macro focusing lens with the tubes (like a Macro Takumar), or any prime like the 1.4 50mm?

2) If i want to use a 100mm lens with tubes do I have to stack 100mm worth of tubes (ie. 2 full sets or 6 tubes) behind the lens to get the 1:1?

I've read quite a bit on this but am unsure of the above.

Thanks!

George

11-26-2009, 07:55 PM   #2
Ash
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Think of it this way:
Using a 50mm lens, 50mm of extension tubes doubles its native magnification.
Don't know what the highest magnification is for the 50/1.4, but let's say it's 1:4, then 50mm of tubes would make it 1:2.
Indeed, 100mm of tubing is necessary to convert a 100mm 1:2 macro to a 1:1 macro.
11-26-2009, 08:27 PM   #3
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Ash sorry but you have that somewhat wrong and that's why there's confusion about this subject. It does not matter what the lens magnifies at if it's a normal lens (non macro). If it's macro, then you get a double effect with tubes added.
So to get 1:1 with a 50mm add 50mm of extension. To get a 100mm lens at 1:1, then add 100mm of extension. So with any lens, just add the same length of the lenses focal length in extension tubes to get a 1:1 ratio.

If the 100mm is 1:2 macro on it's own. Then you are making it 1:1 with a 100mm extension and then if you extend it to it's macro ability, it's now a 1.5 :1 (or 1.5x life sized) but in the real world, when you extend a 100mm macro lens with tubes and then it's own macro extension, the front edge of the lens is so close to the subject, you can hardly get any light in there.

To be sure I just double checked my old Honeywell book that discusses adding a lens to a bellows.
11-26-2009, 08:44 PM   #4
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Aahhhh, thanks to you both. So I can actually get 1:1 w/ my 50mm & tubes. That's exciting! What kind of magnification would I get if I reversed mounted my 50 or say stacked it with my 28mm?

Thanks again!

George

11-26-2009, 08:47 PM   #5
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Have a look at this. it's a tad more complex than a simple answer:

Macro Math
11-26-2009, 08:53 PM   #6
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Right Peter - I did know that, but explained it poorly and too simplistically.
Thanks for clarifying it.
11-26-2009, 09:33 PM   #7
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Thank you for your link Peter. The information in your article cleared up a lot for me. I have a much better understanding now!

Thanks!

George
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