[Leica] CDI tests: was Consensus? Skopar 24mm

[Mikiro <arbos@mac.com>]

At 5:50 AM +0200 00.4.7, Dominique.Pellissier@droit-eco.univ-nancy2.fr
>Tests made by Chasseur d'images : n。 219/dec.99.
>
>The bargraph is graduated from "weak" to "excellent".
>I've chosen the following rating : "weak" =1; "poor"=2;"good"=3;"very
>good"=4;"excellent"=5.
>The first grade is for the center of the lens ; the second for the edge.
>
>Cosina 15 :
>at 4.5 :1.5;1
>at 8 :3;3 (="good,good"). The optimum.
>
>My comment : not too bad for a 15.
>
>By comparison, for the elmar R 3.5/15 (in fact a Zeiss Distagon): 3;2 at
>full aperture and 4;3 at the optimum (5.6 and 8).
>
>Cosina 24 :
>
>at 4 : 1.5;1.5
>at 8 : 3.5 ; 3. The optimum.
>
>By comparison the elmarit M 24 gives :
>
>at 4 : 4;4 (=very good, very good)
>at 8 : 5,4 the optimum.
>
>My comment : no need for a photo finish!
>
>Dominique

Dominique,

I am also a regular reader of this CdI.  I should tell you that their test
results are sometimes very different from what I have felt with my own
lenses.  I am not familiar with how they do MTF tests and rate the results,
but let me point out two things.

1) MTF tests someties give false results because they are easily affected by
measurement conditions.  Asahi Camera also does MTF tests in their review
articles.  When they have results very different from those pubslished by
the manufacturers, they will do tests again with the manufacturers.  In some
cases, a re-test gives better results that are nearer to what manufacturers
officially publish.

2) Some variation in production is unavoidable.  Asahi Camera sometimes
tries a second sample.  The source of the samples is also important.  Some
journals have their test material from manufacturers, which should be one of
their best.

I love looking at MTF charts as well as taking pictures.  However, I do not
rely on one single test.  BTW, if I remember correctly, Aashi Camera
reported very good MTF results with these Cosina lenses.

Amicalement,

Mikiro