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08-02-2012, 08:41 PM   #1
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Is a macro extension tube even possible?

The 01 prime has a focal length of 8.5mm. Even an 8mm extension tube would put the lens into lifesize or more magnification. There probably needs to be electronics( maybe a chip) inside with electrical contacts. Is it even possible to make an extension tube that short? Would love to have one!
thanks
barondla

08-02-2012, 09:39 PM - 1 Like   #2
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Given a minimum focus distance of 0.2m for this lens:
Lens Magnification and Depth of Field Calculator
an 8mm extension tube would give a new minimum focus distance of 0.03m (30mm). This is the distance from the sensor to the object.:

9.2mm = Flange to sensor register for Q mount
8.5mm = focal length of lens
8.0mm = extension tube

total 25.7mm leaving you with 4.3mm (0.17 in) distance from lens to object. Not much working distance for lighting. The filter ring will probably be hitting the object before you get close enough to focus.

I have a glassless Minolta MD to K mount adapter that is 8mm. No infinity focus so it acts like a short extension tube. It probably depends on the design of the latching mechanism for the lens mounts.

Note the above linked calculator is based on the assumption of a thin lens so that the optical center is in the front element. The optical center in a multi-element lens may be elsewhere so the distance from the front element to object could be much less.
08-02-2012, 09:41 PM   #3
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QuoteOriginally posted by barondla Quote
The 01 prime has a focal length of 8.5mm. Even an 8mm extension tube would put the lens into lifesize or more magnification. There probably needs to be electronics( maybe a chip) inside with electrical contacts. Is it even possible to make an extension tube that short? Would love to have one!
thanks
barondla
It definitely looks like it's possible. The 8 mm isn't a big deal, as long as there's no electronics or you don't mind them being outside the 'tube'.
08-02-2012, 10:55 PM   #4
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I think its possible even with electrical contacts.
IIRC from some of the dissection of A or FA lenses on the net, the electronics is just a piece of PCBA located somewhere after the first mount ring.

I've seen fantastic results from pns cameras with a good quality close up filter like a Raynox250, so I'd think that is be easy way to go, while retaining AF, auto exposure, PTTL.
The Prime01 is not suited for these filters though, since its a pretty short focal length and there won't be much magnification when using a raynox 250.
Perhaps the Zoom at the long end with the Raynox will be better.

08-02-2012, 11:21 PM   #5
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To be clear, I was trying (poorly) to say that contacts would be OK but any other electrical circuit might be a hair troublesome for a cheap tube.

Back to the task at hand - I think eventually you'll have a problem with the front of the lens hitting the object rather than magnifying more. Of course the 8mm is so short physically that you might be AOK.
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