# Nikon Micro-Nikkor 55mm AI F/3.5 Lens & M2 Adapter



## avilamillar (Aug 10, 2009)

Hi, i have just won an auction on ebay (60 dlls) for this lens and i was wondering whats the function of the M2 adapter?

I have a Nikon D60, do you think that lens will perform better with the PK-13 extension tube? or even better with the PK 13,12 and 11 together? 

Thanks


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## Garbz (Aug 11, 2009)

The M2 adapter is a matched extension ring, I think somehow designed with the Micro-Nikkor 55mm AI f/3.5 in mind.

I changes the focus range of that lens to 1:2 (not macro really in todays terms) to 1:1.


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## Dwig (Aug 11, 2009)

The special attribute of the M2 ring is that it is 27.5mm long, exactly 1/2 the focal length of the 55mm Micro-Nikkor and exactly the right length to pickup where the lens' own focusing leaves off (1:2) and allow focusing from 1:2 to 1:1.

There have been 4 Nikon extension rings that are 27.5mm long:

M Ring - special to the original 55mm f/3.5 Micro-Nikkor, auto-diaphram but not meter coupling

M2 Ring - sold for the 55m f/3.5 Micro-Nikkor-P, auto-diaphram but no meter coupling

PK-3 - auto diaphram and old-stype "prong" meter coupling

PK-13 - auto diaphram and AI meter coupling

Switching from the M2 to a PK-13 would be of no advantage on a D60 or any Nikon body that doesn't meter with AI lenses.


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## avilamillar (Aug 11, 2009)

Ok, thank you  so with this lense extension it should focus like the new 60mm f/2.8, isnt it?


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## avilamillar (Aug 11, 2009)

Oh, one more question, can i get closer than 1:1??

thanks


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## Dwig (Aug 11, 2009)

avilamillar said:


> Ok, thank you  so with this lense extension it should focus like the new 60mm f/2.8, isnt it?



yes, except that you have to shuffle the extension tube in an out as you cross the 1:2 barrier.

Getting closer than 1:1 requires a bit of a different approach if you want to go much past it. To go a little beyond 1:1 you could add a second extension tube.

To get much higher magnifications you could start out by using a BR-2a reversing ring (Nikon's designation). This mounts your 55mm Micro-Nikkor backwards. If mounted directly on the body you will get around 1:1 or a bit higher magnification. Add an extension tube, like the M2, and you begin to get into true photomacrography. The downside of this approach is that the lens is completely disconnected from the body and you must manually open the aperture to focus and then manually close it to shoot.

Second, the lens' focusing ring will not adjust magnification/focus. You have a fixed focus system. At these magnifications, anything from near 1:1 and higher, to focus by moving the whole camera/lens combination in and out or by moving the subject. To get a continously adjustable system you would use a bellows unit like Nikon's PB-6. The PB-6 provides a wide range of extension and has its own lens reversing ability eliminating the need for the BR-2a ring. Earlier bellows required the BR-2a when you want to reverse the lens.


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## Garbz (Aug 12, 2009)

Bellows would help get you past the 1:1 mag ratio, but you use a lot of light when exceeding the lens specs.


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## Dwig (Aug 12, 2009)

Garbz said:


> Bellows would help get you past the 1:1 mag ratio, but you use a lot of light when exceeding the lens specs.



You do loose a lot of lit in extreme macro (true photomacrography), but not because you are exceeding some lens specification. Its simple physics.

Exposure is not actually controlled by the lens' f/stop; its controlled by the effective f/stop. The format being the ration between the focal length and the aperture diameter (f=focal length and d=diameter hence f/d hence values like f/4...). The effective f/stop being the distance between the lens and the film (focal length plus extension from infinity focus) divided by the aperture diameter. 

As you extend the lens from its infinity focus position it becomed effectively slower. If you focus to 1:1 purely by extension (no internal shifting element focal length change) a lens become 2 stops slower than it was at infinity. At 4x magnification, you've lost another 2 stops or 4 stops total.


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## avilamillar (Aug 12, 2009)

ohh ok... now im understanding better all this 

So i can put M2+M2+lens and it will give me a little more than 1:1 but i didnt really understand the second (sorry for that, im starting in photography) i put the BR-2a reversing ring directly in the camera then i mount the lense backwards there, and then i put the M2 to the lens, so it will be BR-2a+lense(backwards)+M2 

Thank you for the help i really appreciate it.


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## avilamillar (Aug 12, 2009)

A few days ago i ordered Understanding Close-up Photography book by Bryan Peterson, im going to read it and maybe ill understand better.


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## Garbz (Aug 13, 2009)

Thanks for the explanation Dwig. I used the term "exceeding specification" as widely as making it somehow go closer than 1:2. I.e. any extension tube or bellows


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## Dwig (Aug 13, 2009)

avilamillar said:


> ohh ok... now im understanding better all this
> 
> So i can put M2+M2+lens and it will give me a little more than 1:1 but i didnt really understand the second (sorry for that, im starting in photography) i put the BR-2a reversing ring directly in the camera then i mount the lense backwards there, and then i put the M2 to the lens, so it will be BR-2a+lense(backwards)+M2
> 
> Thank you for the help i really appreciate it.



When using extension tubes, they always go between the lens and the camera body, regardless of whether the lens is "mounted normally" or mounted reversed using a BR-2a ring. Usable patterns are:

body - BR-2a - reversed lens
body - M2 - BR-2a - reversed lens
body - M2 - M2 - BR-2a - reversed lens
body - M2 - normally mounted lens
body - M2 - M2 - normally mounted lens
and so forth.

When mounting a reversing adapter directly on a modern body, you must use the BR-2a ring and not the older BR-2 ring. The old version can damage some bodies.


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## avilamillar (Aug 14, 2009)

Ohh ok ok thank you for the explanation and tip... my lense will arrive in a few hours


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