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Archive 2017 · Experimenting with a Reversed Laowa 7.5mm on m4/3

  
 
e6filmuser
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p.1 #1 · p.1 #1 · Experimenting with a Reversed Laowa 7.5mm on m4/3


My main macro lens in recent months has been the Olympus 4/3 50mm f2 macro. This gives a maximum magnification on FF of 1:2, on m4/3 of 1:1. To increase this, I either put an MSN-202 (25 diopter) Raynox on the front or put an Olympus 4//3 x2TC behind the lens. For a FOV ca 6mm wide I use all three. The working distance is around 20mm.

I have recently obtained a Laowa 7.5mm for m4/3. Turning it around gives a FOV 4mm wide at a WD of ca 12mm.

Thus, the Laowa gives the propect of a bit more magnification with a lot less glass.

For this session I used a tiny cactus with very finely-divided, feathery spines. They are held flat against the spherical plant body, raising severe issues of DOF, of which there is very little at such a magnification anyway.

I took a series a of shots with each setup. I used triple, off-camera TTL flash but problems of getting the light past camera, lens and hands were considerable with the 7.5mm. Anyway some light got onto the subject.

The camera was hand-held, a tripod being necessary for a more serious test, but it would have been ver awkward to use. Getting the focus and framing with the Laowa was very difficult.

Both lenses were used at f16 (effective for the Olympus). Software has been used to deal with diffration blur.

I have shown here the best image for each lens. It is important to look at the best-focused parts of each image because of the curved subject. I have then shown cropped images at about the same magnification.

My conclusion is that the reversed Laowa gives similar result to those of the Olympus setup, at least enough to make further tests worthwhile.

For this session, the Laowa was used with the focus ring at infinity. More testing with the setting is desirable.

As for useful applications for the reversed Laowa, they are very limited, but it is just right for slime mould fruiting bodies, which I like to photograph.

Harold





Harold Gough 2017


Olympus setup FOV ca 6m







Reversed Laowa FV ca 4mm





Harold Gough 2017


Cropped Olympus





Harold Gough 2017


Cropped Laowa




Aug 13, 2017 at 01:49 AM
surfnron
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p.1 #2 · p.1 #2 · Experimenting with a Reversed Laowa 7.5mm on m4/3


Interesting Harold, but these results would not work for me. I like tack sharp images - especially so with macro ~ Ron


Aug 13, 2017 at 08:31 AM
JohnK007
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p.1 #3 · p.1 #3 · Experimenting with a Reversed Laowa 7.5mm on m4/3


surfnron wrote:
Interesting Harold, but these results would not work for me. I like tack sharp images - especially so with macro ~ Ron


+1

It looks more like severe diffraction than lack of sharpness.

What aperture did you set?



Aug 13, 2017 at 11:38 AM
e6filmuser
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p.1 #4 · p.1 #4 · Experimenting with a Reversed Laowa 7.5mm on m4/3


surfnron wrote:
Interesting Harold, but these results would not work for me. I like tack sharp images - especially so with macro ~ Ron


JohnK007 wrote:
+1

It looks more like severe diffraction than lack of sharpness.

What aperture did you set?


Thanks for your responses.

The aperture was f16, nothing extreme, and I processed for diffraction blur.

It seemed to me that the subject had been unhelpful in showing what the lens could, or could not do, reversed.

Today I had a long session, with just the reversed Laowa, and at various focus settings on the focus ring. I used a subject which I though might give better results, a slime mould with very fine structures.

The details in the viewfinder looked promising but I was unable to get them sharp in PP.

I did not purchase the lens to use it is this way but someone elswhere suggested it might be worth trying. It was but this is the end of my interest in this potential application. It performed superbly today as an ultra wideangle lens.

This makes me all the more interested in what the Zhongyi Mitakon 20mm F2 4.5x Super Macro can do.

Harold



Aug 13, 2017 at 12:47 PM
e6filmuser
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p.1 #5 · p.1 #5 · Experimenting with a Reversed Laowa 7.5mm on m4/3


Just to capture a thought:

The reversed Laowa will focus only at a little more that half the register distance (flange to sensor). This is beyond my knowledge and understanding of optics but I suspect that it may limit sharpness.

Harold



Aug 14, 2017 at 12:52 AM
JohnK007
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p.1 #6 · p.1 #6 · Experimenting with a Reversed Laowa 7.5mm on m4/3


I just tried my Nikkor 20mm, reversed, with a Kenko 36mm extender on it. Without the extender it gets 3.4x. With the extender, it goes to around 5x. I personally only used f/4 for this ... due to diffraction ... so I would imagine f/16 at 9x might be part of the problem you experienced.

Here is an uncropped image of the proximity I was able to get: the corner of a US dime: Not as sharp as without the extender, but closer.







Aug 14, 2017 at 05:21 AM





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