Metabones Y/C SpeedBooster Meets Voigtländer 58mm f/1.4

Started Oct 13, 2013 | Discussions thread
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David Kieltyka
David Kieltyka Veteran Member • Posts: 5,166
Metabones Y/C SpeedBooster Meets Voigtländer 58mm f/1.4

Last night I tried out my Yashica/Contax-mount SpeedBooster on the Panasonic GX7 with an M42 screwmount lens, the Voigtländer 58mm f/1.4, via an M42-to-Y/C adapter. The lens is branded Tokyo Optical, aka Topcon, and was made by Cosina with Topcon's permission for a short time c. 2004 or so. It's a recomputed version of the original 58mm f/1.4 Auto-Topcor from the early 1960s.

Taken w/ Panasonic GX7 + SpeedBooster & Zeiss 60mm Makro-Planar C @ effective f/2.8.

For a quickie test I set up on a tripod and took some pics of an old painting in my rec room. The SpeedBooster converts the Voigt/Topcor into a 41mm f/1.0 lens. Here's the painting at f/1.0, cropped to 16x9 to eliminate the boring background wall. Note that the painting wasn't centered in the frame top-to-bottom...rather I placed it up near the top to get a better read of the lens' corner performance. As it turned out, though, a bit of field curvature combined with the slight forward lean of the painting at the top resulted in sharper corners up top than at the bottom!

GX7, SpeedBooster & Voigt/Topcor 58mm lens @ effective f/1.0, ISO 200.

Now here's a full-res crop from the bottom right corner of the painting. Resolution & contrast drop away from the central third of the image but it's gradual in both cases.

Full-res crop, bottom right corner.

At f/1.0 overall saturation & contrast are reduced relative to smaller apertures but not by all that much. There's some corner light falloff too but, again, not all that much. At f/1.4 there's very little difference in image quality or in exposure time (1/6th sec. @ f/1.0, 1/5th sec. @ f/1.4)...corner falloff improves marginally and DOF increases. At f/2.0 corner falloff is gone and the image crispens across the frame. At f/2.8 the image is very crisp throughout...stopping down further gets you a very marginal improvment at f/4.0 but only greater DOF from there on down. Just a tiny hint of diffraction softening at f/11. Other pics I took around the house bear this out. Here's the same bottom right corner at f/2.8.

GX7 + SpeedBooster & Voigt/Topcor 58mm lens @ effective f/2.8, ISO 200, full-res crop.

Just for kicks here's an off-the-cuff pic I took while testing the GX7's focus peaking accuracy with the Voigt/Topcor. At close range, one meter in this case, peaking is good enough that there's no need to magnify the image in the EVF. Due to the very shallow DOF at f/1.0 there's an almost 3D quality to this photo...look carefully at the film titles on the Blu-ray cases and you may see it. The films all have something in common too (three of 'em have two things in common)...know what it is?

GX7 + SpeedBooster & Voigt/Topcor 58mm lens @ effective f/1.0.

Once again I'm impressed with what the SpeedBooster does to my lenses!


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Leica M9-P Leica M8.2 Pentax 645D Panasonic Lumix DMC-GX8 Leica M10 +7 more
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