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Wide angle Lenses with focal lengths shorter than 14mm.

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Old 13th August 2017
Harold Gough Harold Gough is offline
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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







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