KOWA PROMINAR 8.5mm F2.8 Test and Review (English version)

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Introduction:

KOWA is one for the famous company in telescope and telescope lens player starts to involve the design and manufacture the lens of M4/3 system. They have show the new product line in the Inter BEE show at end of 2013 the fixed focal length prime lens of M4/3 (http://vimeo.com/79305426). The first lens published at Sep 2014 is the “ PROMINAR 8.5mm F2.8” we want to introduce to you today. It is the first M4/3 ultra-wide non-fisheye fixed focal length lens in the world. The viewing angle is 91 degree in horizontal and equivalent to 17mm in 135 film system.

 

Appearance of KOWA PROMINAR 8.5mm F2.8

Specification of KOWA PROMINAR 8.5mm F2.8

Here are the specifications of KOWA PROMINAR 8.5mm F2.8.

Focal length: 8.5mm
Aperture range: F/2.8 to F/16
Optical: 14 group 17 elements
Viewing angle: 93.5 degree(H) x 77.1 degree(V) x 106 degree(D)
Focusing distance: 0.2m to infinity
Magnification: 1/12.5
Largest viewing area: 239mm x 179mm
Filter thread: 86mm on Hood, 67mm on Lens
Dimension: 71.5mm(L) x 86.8mm(D)
Weight: 440g 

This lens is modified from the LM8XC 4/3 inches CCTV lens. The appearance size looks much like.

LM8XV Outlook

Specification of LM8XC

It’s original M4/3 mount ultra-wide lens with 8.5mm focal length (equivalent 17mm for 135 film system). Maximum aperture F/2.8, close focusing 20cm, manual focusing and iris, dimension 71.5mm(D) x 86.8mm(L), weight 440gram. The iris has no stepper so very useful for taking movie. Not only the Panasonic or Olympus Camera body can match for this lens but also the BMPCC. But BMPSS has smaller sensor size, this lens’s coverage seems too border to them, anyway it match BMPCC. 

The optical of this lens is just as the above, 14 groups and 18 elements. Why the structure of this ultra-wide lens is such complicate? It must be for the barrel correction(you will know that at the distortion test). Regarding the KOWA released document, this lens include the floating optical element design(FLE), to get the optimum optical specification from short to long object distance. Because the traditional optical design only can get the best optical performance at infinity object distance(in general is longer than 100x focal length or 3 meter). But the floating element design using the focal ring to  synchronize tuning the element to optimize the optical aberration, then to get the best resolution and contrast result from short to long object distance.

First Impression:
Kowa offers black white and green versions of this lens. We get the black one from Kowa. In the box has lens, front and back caps, hood and punch. This lens is the largest M4/3 lens since we ever review. Appearance of it is a little longer and wider than Olympus M.Zuiko 75mm F1.8. It’s build by all metal components include focal ring, iris ring, mount and everything. Non of them are plastic. And the build quality is solid. By the way this is a manual control lens.

A special design for this lens is the iris ring that can be set to step or smooth by a stick button. The step of iris ring is 1EV. The focal ring is well damped. The other excellent design is the filter threads that is 86mm for hood and 67mm for lens. Compare to most of the ultra-wide lens they can’t be mounted with any filter this is really a fantastic design.

Step iris ring

Smooth iris ring

You can see a little weird outlook when we mount this big ultra-wide lens to a tiny Olympus E-PL6 camera body. Anyway this is the first M4/3 ultra-wide angle with fixed focal length lens in the world. We are happy and eager to take a look at the performance. 

Test start:
This test is Kowa PROMINARP 8.5mm F2.8 lens on Olympus E-PL6 camera body. Some of the test result will be compare to the other lenses with similar focal length. If you want to know about the detail of test procedure please refer “Basic of lens test on Olympus E-PL6”.

Vignetting:

The vignetting on maximum iris is around 1.5EV. There are still have some vignetting like 1EV from F/4 to F/11. This could be from the sensor’s incidence light angle is too oblique, due to the ultra-wide angle of view.
 

F/2.8

F/4

F/5.6

F/11

Distortion:

There are no barrel distortion. Never seen such low distortion on ultra-wide lens. We rank it “Excellent”.

Distortion of Kowa PROMINAR 8.5mm F2.8

Distortion of Olympus M.Zuiko 12mm F2.0

Resolution:

Here are the frame center resolution with aperture F/2.8, F/4, F/5.6, F/8, F/11 and F/16(left is sagittal and right are tangential). The optimum resolution is around F/5.6 where the resolution is around 3300 lines. In general It’s pretty good from F/2.8 to F/8. After F/11 the resolution degrade to 3000 lines. At F/16 the resolution still have 2700 lines. So it is better to keep using the aperture below F/11 for keeping the best resolution.

   F/2.8 Sagittal & Tangential resolution on center

 

F/4 Sagittal & Tangential resolution on center

 F/5.6 Sagittal & Tangential resolution on center

 F/8 Sagittal & Tangential resolution on center

F/11 Sagittal & Tangential resolution on center

 F/16 Sagittal & Tangential resolution on center

Here are the sagittal(left) and tangential(right) resolution at center, 1/2 and border with aperture F/5.6. The resolution on 1/2 frame is slightly degradation, and get sagittal 3300 lines, tangential 3000 lines on the border. It keep the high resolution within 1/2 frame and slightly degradation till to border, is pretty good for an ultra wide lens.

 F/5.6 Sagittal & Tangential resolution on center

F/5.6 Sagittal & Tangential resolution on 1/2 frame

F/5.6 Sagittal & Tangential resolution on border

Go through all about the resolution. We rank it “Above average”.

Chromatic:

Here are the chromatic at corner on F/2.8, F/5.6 and F/11(from left to right). We rank it “Average”.

 Chromatic at corner on F/2.8, F/5.6 and F/11

Flare:

The flare we rank it “Average”.

Flare under light source in the room

Sun Star:

Here are the sun stars at indoor simulation light source. There is a little partical around the star. We rank it “below average”. 

 

 

 Sun star of Kowa PROMINAR 8.5mm F2.8 at indoor simulation

 

 Sun star of Olympus M.Zuiko 12mm F2.0 at indoor simulation

 Sun star of Olympus M.Zuiko 17mm F1.8 at indoor simulation

 Sun star of Panasonic G 14mm F2.5 at outdoor

Coma Aberration:

Here are the coma at center(left) and corner(right). We rank it “Average”.

 Coma at the center and corner

Chromatic and Coma effect of Panasonic G 14mm F2.5

Magnification:
The magnification of this lens is (17.3mm/220mm)=0.079

Details of picture:

There are no detail lose at maximum iris. It’s wonderful.

F/2.8

F/5.6

F/11

Defocus Aberration or Bokeh:

In general the wide angle lens is not easy to get the bokeh. But this one seems not bad. The shape of bokeh keep circularity even the iris is small.

F/2.8

F/5.6

F/11

Conclusion:

This lens retail price is US$1200 at eBay. Why this lens is so expensive? We think there are two reasons. 1.The optical structure is complicated so the manufacture cost is high. 2.This is the only one fast ultra-wide lens with M4/3 mount today. So let’s look forward to the other company offer something like this in the future.

Regarding this lens “Kowa PROMINAR 8.5mm F2.9”, the ranking for each item is

Vignetting: “Average”
Distortion: “Excellent”
Resolution: “Above Average”
Chromatic: “Average”
Sun star: “Below Average”
Coma: “Average”

To sum up each test item our ranking for this lens performance is “Average”. Considering the market have no other choice today. We recommend it is worth to try.

PS. After trying to mount the 67mm filter to the lens. We found the filter thread pitch is not common 0.75mm. So we just can screw it for 1/4 circle, anyway it works.

More sample pictures are at "KOWA PROMINAR 8.5mm F2.8 Sample Pictures".