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Working out 1:1 macro with tubes?
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PostPosted: Sun Jan 30, 2011 10:58 pm    Post subject: Working out 1:1 macro with tubes? Reply with quote
I have a selection of MF lenses and have a set of 3 M42 extension tubes. How do i know when i have reached 1:1 magnification on a given lens? Is there a formula?

My extension tubes are 6mm, 19mm & 26mm plus they can be stacked.

Thanks


PostPosted: Sun Jan 30, 2011 11:08 pm    Post subject: Reply with quote
Shoot a ruler. If you see about 22-24mm wide of that ruler, you reached 1:1 on a APS size sensor camera (size depends on the APS type camera you have). FF would be 36mm.


PostPosted: Sun Jan 30, 2011 11:15 pm    Post subject: Reply with quote
Sorry i don't understand that at all?????


PostPosted: Sun Jan 30, 2011 11:28 pm    Post subject: Reply with quote
Or photograph some 1cm graph paper. Two horizontal squares is about 1:1

If you already know the lens native magnification, the formula is here: Macro Extension Tubes and Closeup Lenses


PostPosted: Sun Jan 30, 2011 11:33 pm    Post subject: Reply with quote
Got it

Lovely, Thanks Smile


PostPosted: Sun Jan 30, 2011 11:59 pm    Post subject: Reply with quote
With the lens at the marked infinity focus position you should reach 1:1 by adding extension equal to the focal length of the lens.

(i.e. for a 50mm lens add 50mm worth of tubes and you should have 1:1 with lens at infinity and slightly more if you use the lens to focus even closer)


PostPosted: Mon Jan 31, 2011 12:17 am    Post subject: Reply with quote
kds315* wrote:
Shoot a ruler. If you see about 22-24mm wide of that ruler, you reached 1:1 on a APS size sensor camera (size depends on the APS type camera you have). FF would be 36mm.


So 1:1 would be the same focus position on any sensor?!? Surprised

(If you put the same lens on ff and aps)


PostPosted: Mon Jan 31, 2011 12:40 am    Post subject: Reply with quote
Nordentro wrote:
kds315* wrote:
Shoot a ruler. If you see about 22-24mm wide of that ruler, you reached 1:1 on a APS size sensor camera (size depends on the APS type camera you have). FF would be 36mm.


So 1:1 would be the same focus position on any sensor?!? :o

(If you put the same lens on ff and aps)


Yes, magnification means the size of the image on the sensor, i.e. 1:1 means that the image of the object is life-size on the sensor. On APS-C you can fit about 24×16mm in the image at 1:1, on FF about 36×24mm. If both images are printed/viewed at the same size, then the APS-C image will look “more macro” (because APS-C needs to be enlarged more to reach the same size). Of course you could just crop the FF image to APS-C size and they would be identical (save for possibly different pixel pitch in cameras).


PostPosted: Mon Jan 31, 2011 1:59 am    Post subject: Re: Working out 1:1 macro with tubes? Reply with quote
andyw wrote:
I have a selection of MF lenses and have a set of 3 M42 extension tubes.

What, only one set of tubes? That's hardly enough! They're so useful for other things than macro shooting, like for adapting lenses. But I digress.

Some of the info on the link visualopsins provided may be a bit confusing. Here is the simple way to determine magnification:

MAG = (TE-FL) / FL where MAG is magnification, TE is total extension, and FL is focal length.

So if you put a 50mm camera lens, focused to infinity, onto 100mm of extension (tubes and/or bellows), then TE= 50+100, and MAG= 100/50 = 2X (2:1). Focusing the lens closer than infinity increases total extension and magnification somewhat.

A camera lens has extension equal to its focal length already built into its body. An enlarger lens doesn't. If a 50mm enlarger lens is put on 100mm extension, then TE= 100, and MAG= 50/50 = 1X (1:1).

Your wee measly little M42 macro tube set only stacks to 51mm. That's enough to push a 50mm camera lens to 1:1, but longer lenses demand more tubes and/or bellows. I use two M42 bellows and about 6 sets of tubes. That's barely enough to push my Spiratone 400mm with a 2X TC towards 1:1.

Something to keep in mind: No lens can focus closer than its focal length, and that is also the distance for greatest magnification. That is true no matter how much extension is used. Put 250mm extension on a 50mm camera lens for 5:1 magnification, and you still can shoot no closer than 50mm. We often use longer lenses for macros because we get greater working distance.
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