PROMINAR 12mm with the α7S ii

Using M43 lenses with Sony E bodies (3)

A review and photo examples of using the KOWA PROMINAR 12mm F1.8 with the SONY α7S ii.

Please see the disclaimer regarding advertising here.

This is an irregular way to use a lens, and we would like to point out that anyone attempting similar photography does so at their own risk.

KOWA PROMINAR 12mm F1.8をSONY α7S iiで使うレビューと写真作例

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Gallery

The sample photos were taken with the PROMINAR 12mm and SONY NEX-7.

1．Overview

When using a Micro Four Thirds lens with a Sony E mount, a dedicated mount adapter is required.

The flange back of the Micro Four Thirds lens is 20mm, while that of the Sony E is 18mm, a difference of 2mm. Commercially available mount adapters only physically convert the mount shape.

With the technology available in 2024, due to the thickness of 2mm, an adapter that adds electronic contacts between the lens and camera and incorporates a circuit to convert electrical signals has not been realized.

Mount adapters currently available in 2024 cannot do the following, so the following problems occur with autofocus (AF) lenses provided by Olympus and Panasonic.

AF cannot be used
Electrical aperture cannot be controlled
Some lenses have vignetting due to insufficient image circle

Specifications of the sensor and mount of Micro Four Thirds and Sony E

	Micro Four Thirds	SONY E
Sensor size	17.4mm × 13.0mm	23.6mm x 15.8mm
Sensor diagonal distance	21.72mm	28.4mm
Flange back	20mm	18mm

This time, we will report on the results of shooting with the KOWA PROMINAR 12mm F1.8 attached to the SONY α7Sii using the SHOTEN Mount Adapter m43-SE (Micro Four Thirds lens to Sony E-mount conversion), one of the mount adapters that converts the physical mount shape.

2．Usability

The actual results of the α7Sii showed that the center can be used at 1:1, as expected with the NEX-7. The gallery shows images cropped to the practical range.

NPROMINAR 12mm	撮影範囲（横 x 縦ピクセル）	35mmフルサイズセンサーに対する割合
マイクロフォーサーズ	2035 x 1529	横 48% 縦 54%
ソニーFE	4240 x 2832	–
実用可能範囲	2035 x 2035	横 48% 縦 72%

As shown in the image below, the lack of an image circle can be seen with a 35mm full-frame sensor. The Sony 35mm full-frame mirrorless α series has an APS-C/Super 35 crop mode, so when used with this the number of pixels is reduced by the amount of cropping, but the results are the same as when used with an APS-C size sensor camera.

When the PROMINAR 12mm is practically cropped from the results of shooting with a 35mm full-frame sensor, it becomes equivalent to a focal length of 21mm with a 1:1 square shooting range. When shooting a straight object, if it exceeds the set sensor size, it will be significantly distorted. It is thought that the aspherical lens properly corrects only the part that is being used.

PROMINAR 12mm	35mm equivalent focal length	Conversion Factor
Micro Four Thirds	24	2
SONY FE	12	1
Practical focal length	21	1.7

This mount adapter is very thin, so you first attach the mount adapter to the lens, and then attach it to the camera body.

Once the lens and mount adapter are attached, attach the lens to the camera.

In reviews from previous users, I had seen information that the mount adapter was tight, but the mount adapter and lens I tested this time connected smoothly and could be removed smoothly as well.

3．Add info.

As for Olympus (OM-SYSTEMS) lenses, the 9mm f8 Fisheye Body Cap Lens BCL-0980 seems like it should be usable because it is a manual focus lens with a fixed aperture, but when I actually tried to attach the lens to the mount adapter, it would not fit.
Observing the lens, I found that the mount of the BCL-0980 is plastic, and the tabs that connect it to the mount are thicker than the tabs on a metal mount. This is why it did not fit into the mount adapter, and it is likely that only the dimensions of the metal mount were taken into consideration when the mount adapter was designed.

The OLYMPUS Body Cap Lens for Micro Four Thirds BCL-1580, which has the same plastic mount, may also be difficult to attach.

Voigtlander has released six large aperture lenses for Micro Four Thirds, and since they are manual focus lenses and have a real aperture, they should be usable.
I have not tested any lenses other than the NOKTON 25mm, so there may be some lenses that cannot be attached, like the BCL-0980.

10.5mm F0.95 / 21mm
17.5mm F0.95 / 35mm
25mm F0.95 / 50mm
29mm F0.8 / 58mm
42.5mm F0.95 / 85mm
60mm F0.95 / 120mm

Kowa has released the following three lenses, which are manual focus lenses with real apertures and should be usable. As they have not been tested, there may be some lenses that cannot be attached, such as the BCL-0980.

PROMINAR 8.5ｍｍ F2.8
PROMINAR 12mm F1.8
PROMINAR 25mm F1.8

In addition, it is thought that manual focus and actual aperture lenses made overseas can be used, but there may be some lenses that cannot be attached depending on the structure of the mount.

Specifications (reprinted from SHOTEN official website)

Model name	m43-SE
Compatible Lens Mount	Micro Four Thirds Due to its structure, adapters that convert Micro Four Thirds lenses to Sony E-mount may not fit smoothly. Please understand that lenses from emerging manufacturers may vary slightly in size and fit, so there may be some stiffness, looseness, or slight play when fitting.
Compatible Camera Mounts	SONY E
Other specifications	Material: Brass Weight: Approx. 30g
remarks	When using, set the camera’s “Menu” – “Release without lens” to “ON.”
Notes	The lens cannot be electronically controlled. If an electronically controlled lens is attached, focusing and aperture adjustment may not be possible. Attach the adapter to the lens first, and then attach it to the camera. The lens cannot be attached while the adapter is attached to the camera or if there is a cap on the body side of the adapter. Micro Four Thirds lenses have a small image circle, so the corners of the screen may become black.