Mamiya-Sekor F.C. 1.7/58 - a photo on Flickriver

MAMIYA-SEKOR F.C. 1:1.7 f=58mm

I found some hints on the web, that this lens has the same lens formula like the Biotar by Carl Zeiss. I hope, that those hints are not only based on the fact, that both lenses have a focal length of 58 mm. Well, at least I saw some sample pictures with swirly bokeh, so the assumption could be right.

This lens belongs to the Mamiya Prismat and Prismat NP and has an Exakta lens mount. On those cameras the aperture is semi-automatic, for this the small linkage is required you can see in the foreground or here, mounted. You can easily unscrew it if needed, e.g. to mount the lens onto this Exa Ia.

To open the aperture for proper viewing you have to press the lever on the left side until it clicks, the lever should return automatically. To close the aperture to the selected value you have to pull away the tiny silver button on the right side away from the lens (On the Prismat camera this is done automatically with that linkage, when you press the shutter button). You can set another f-stop at any time; the aperture ring is locked by a small button.

Nearest focal distance: 0.5 m
Number of blades: 9
Filter thread diameter: 52 mm

There should be an M42-version of this lens, made for the Mamiya CWP.

Sample picture: here

Meanwhile I have the idea, that this semi-automatic aperture is a design by Topcon, but I still don't have a proof.

Taken on: December 23, 2016

Tags:

mamiya

sekor

1.7

58mm

biotar

lens « less

Sets appears in: • ordinary exposure tools

Camera: Pentax K-7, f/9.0, 1/180 sec, 50mm (=75mm), ISO 100 (more info) (hide info)

Camera:	Pentax K-7
Aperture:	f/9.0
Exposure Time:	0.006 sec (1/180)
Focal Length:	50mm (35mm equivalent: 75mm)
ISO:	100
Exposure Bias:	-1 EV
Flash:	Off, Did not fire
Exposure Program:	Manual
Exposure Mode:	Manual
Metering Mode:	Multi-segment
White Balance:	Auto
Color Space:	sRGB
Software:	GIMP 2.8.16
Show full info

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