Comparison of my 
Minolta MD W.Rokkor 24mm 1:2.8 
against a 
Kiron 24mm 1:2.0 
borrowed from a friend

Hans-Joachim Weber (2005-10-20)

 

Due to a post in a Minolta forum highly praying the optical qualities of a Vivitar 24mm 1:2.0 (manufactured by Kiron) that this Kiron lens is able to rival the world famous Minolta W.Rokkor 24mm 1:2.8 wich was sold as identical optical construction under the following labels.

MC W.Rokkor 1:2.8 24mm

Leica Elmarit-R 24mm f/2.8

MD W.Rokkor 1:2.8 24mm

and my example

MD W.Rokkor 24mm 1:2.8

The Rokkor 24mm is one of my absolute favorites in the Minolta lens line and so I was highly interested to make a comparison of this Kiron design against my Rokkor. Years ago I had compared my Rokkor against a Canon FD 24mm, a Nikon 24mm and a Soligor 2.8 24mm and none of these lenses was able to beat the Rokkor 24mm.

So I doubted from the beginning that the Vivitar/Kiron lens was able to beat the Rokkor. Last week I got the opportunity to borrow a Kiron 24mm f/2 with Minolta MD Mount in mint condition from a  friend of mine and shot a roll of Fuji Sensia 100 ASA with a havy tripod and my Minolta XE-5 body. 

Here a picture of the tested Kiron lens:

 

The tested lens is labeled: KIRON 24mm f/2 55 MC 2020nnnn KINO PRECISION JAPAN
nnnn stands for the rest of the serial#   

To clarify things here are some of my results scanned at 4000dpi with identical settings for all scans on a Nikon V ED. Please keep in mind, that this scanner is not able to resolve all the details a 100 ASA slide shot with a top performing lens contains! But I watched the slides with a 100xStereo Microscope and also with a Leitz Pradovit equipped with a Colorplan 2.5/90mm lens and confirm, that the scans really show the differences. 

The first picture I present here compares the lens performance at infinity in a simple Landscape shot at f8 Mode A (automatic exposure about 1/500s) with a manual override of -1 f-stops to reduce the influence of blooming effects in the film.

Example 1: Landscape shot "Wildbachtal" at infinity and f8
Upper left: 2.4x1.8mm crop from the Minolta MD W.Rokkor 24mm 1:2.8 slide
Upper right: 2.4x1.8mm crop from the Kiron 2.0 24mm slide 
The picture below these two crops shows the whole scenery 
in the original scan from the Kiron picture 

The little square on the right side of the frame shows the location of the two 2.4x1.8mm crops. 
The crops are shown in 100% view of the 4000dpi scans (corresponding about 21Megapixels)   
 


In the crops we can see a clear visible advantage of the Rokkor lens against the Kiron design due to a much better flat of field correction at infinity for the Rokkor lens. Especially the contrast and resolution of the Rokkor are clear superior. In the center both lenses performed nearly identical with only a very little advantage for the Rokkor.

Very important to me for a 24mm lens is the performance in close distances because most often we place a subject in the close distance for wide-angle shots. For testing the close focusing performance of the lenses I choosed to place my XE5 in front of a wall in 50cm distance and took the following shots. Again I provide two 100% crops for you to compare yourself.

Example 2: Center crops of the "Wall shot" taken from near distance 0.5m at f5.6-8. 
Again on the left side the 4000dpi scan of the Rokkor picture compared to 
the scan of the Kiron picture both in 100% view

Once more the winner is the Rokkor but the difference is really small and 
the Kiron lens reaches nearly the performance of the Rokkor.


Conclusion:

The Kiron lens in my tests performed very good, much better than other 24mm third party lenses I tested earlier. Especially a example of a Soligor 2.8/24mm also with Minolta MD mount I tested years ago did not even come close to the performance of the Kiron. In many situations the Kiron lens might deliver comparable results to the Rokkor 24mm. Center sharpness of the Kiron at f2.8 and f4 clear beats that of my Rokkor. But you have to live with significant light fall off to the corners at those apertures.

At f5.6, f8 and f11 (my last tested f-stop) the Rokkor clear delivers the better pictures from center to edge. In the center the sharpnes is very close but the Rokkor shows better contrast. Going to the edges the Rokkors advantage increases even more, now not only concernig contrast but now also concerning sharpness.  

But there remain some additional optical drawbacks of the Kiron lens against the Rokkor:

  1. Flatness of field at infinity is clear worse compared to the Rokkor with its floating element construction. Especially a concern for infinity landscape or architecture shots.

  2. Overall contrast of the Kiron is slightly worse compared to the Rokkor pictures so I think the Minolta achromatic coating does a better job.

As advantage of the Kiron you have better center sharpness at 2.8 and 4, a full f-stop more wide open and usually a Vivitar/Kiron 24mm 2.0 is noticeably cheaper. Also the front is not rotation during focusing what is a advantage when using a polarizing filter.

For me the Rokkor still holds a remarkable advantage concerning "best possible picture quality". People like me that really want to get out the best quality in the 24mm league for the Minolta manual focus system have to go (or have to stay) with the Rokkor. Stopped down to f5.6 the Rokkor delivers picture quality the tested Kiron Lens cannot give to you. 

Hans-Joachim Weber

(c) October 2005  

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