First tests of 3D printed Lieberkühn reflectors

Here I will report my initial tests of my Lieberkühn reflector designs, “hot” off the 3D printers at Shapeways. DSC_0503

I am testing a squeeze-to-attach Lieberkühn that roughly fits a Canon f/3.5 20mm focal length macro lens (above), and a 58mm threaded version (below), tested with a Canon 35mm f/2.8 manual tilt shift lens. I used a Canon auto macro bellows and a Nikon D5100 with an adapter for all test images.
DSC_0512 I haven’t added any reflective material to them yet, so they are essentially “Lieberkühn diffusers” for these tests. I used a domestic desk lamp with a 750 lumen halogen bulb to illuminate the specimens, for slightly off-axis trans illumination.

DSC_0528These are the legs on a cicada molt from last year’s 17-year brood. The photo was taken with the 35mm Canon tilt-shift lens at about the shortest macro-bellows distance possible.

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And here is a shot of the same view with the reflector attached. I used a 1/13 second exposures at ISO 1600 and f/5.6 for both shots.

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The large claws up front with (below) and without (above) the reflector. Again this was taken at f/5.6, an ISO 0f 1600, and 1/13 second exposure time. I increased the bellows distance slightly for this shot, increasing the magnification.

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Although the fill light is definitely better in the shots with the reflector, in some cases a photographer may prefer the image without using it, e.g. to bring out the small details with shadow. The cicada molt is partially transparent, giving a nice effect to the light transmitted through the subject.

I took the two photos of a leaf-cutter bee (Megachile genus, female) below with the same setup. The difference in lighting with and without the reflector is pretty drastic.

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I made the next two pairs of photos using the 20mm macro lens and the squeeze Lieberkühn reflector. The photos contain some apparent lens flare resulting from the off-axis light source, manifesting as a slight general brightening (and resulting loss of contrast) in the middle of each image. I am not sure if the aberration is reduced with the addition of the reflector or if it just looks that way due to the rest of the image being brighter. Looks like a job for some quantitative comparisons, for the next post.

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The position of the lamp and bellows stand were maintained for each pair of images. The bellows was set at the same distance but displaced between exposures to make room to attach the reflectors without disturbing the subjects, so the comparison images may be focused ever-so-slightly at different depths.

The lighting was definitely improved by the use of reflectors for these (mostly opaque) subjects. The images above were intended as a qualitative investigation, I will be looking into the performance and useability of the designs further.

As a final note, compare the print of the 58mm threaded reflector with the render from the STL file. The consistency is inhomogenous, with some bulges introduced during manufacture that were not part of the design file. Can’t say that I’m impressed with the print quality.

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render58mmLR

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