Mini-review: Cosina MC COSINON-W 35mm f/2.8

( 2011-09-26)


I got this lens as a present shortly after I acquired my Pentax K1000 with a SMC Pentax-M 50mm f/2.0 standard lens in 1982. As things happened, I never got to use that lens very much - I found it just to close in focal length to my 50mm Pentax-M and I didn't care much for wide field photography in those days anyway - except for astrophotography where I do remember that I was actually quite pleased with the constellation images it provided.

So, it has been lying in my cupboard, essentially unused, for about 30 years. But recently, I got the SMC Pentax (K) 35mm f/3.5 lens, renowned for its excellent image quality and sharpness even wide open.

And for any fast or moderately slow lens, I demand that it should produce, if not perfect then at least useful and more than merely "almost-acceptable" images even at its widest aperture. Why bother to buy a reasonably fast lens if you have to stop it down in order to produce decent images?

So, since this Cosina is one half stop faster than the Pentax K, I decided to give it another try after these 30 years, starting at the fully open aperture end. Time has not permitted a more thorough test yet, instead I have made a side-by-side comparison between the COSINON-W @ f/2.8 and the Pentax-K @ f/3.5 with images taken under identical conditions just a few minutes apart. A few images with the two lenses stopped fully down to f/22 (indoor images, using flash) are included for preliminary, further reference.

I did this test yesterday (25 September) on a pleasant sunny day - and I got something of a surprise.....

But first a few words on

The lens(es)

The build quality of the SMC Pentax K-series is well known - all-metal very reliable designs with a truly solid feel. So how does the outsider Cosina MC COSINON from about the same era compare? Well, actually quite well. This is also an all-metal & rubber design. Although it has a wider aperture, it is noticeably lighter, weighing 151 grams vs. 165 grams for the Pentax.

It is also slightly more compact, as the following comparison images show:


One should note that the Cosinon is black anodized on the rear flange, which means that I cannot get focus confirmation or use catch-in focus with my older Pentax *ist DL body, whereas I have no issues with the lens on my K200D body, (never thought of that difference before....).

In one aspect, the Pentax lens is more advanced than the Cosina: Both lenses only have a full f-stop on the aperture ring between f/16 and f/22, but the Pentax has half stops all the way from f/3.5 to f/16 while the Cosinon only has full f-stops between f/2.8 and f/16. This may be a constraint in certain situations to get the exposure just right.

But all in all, the Cosina MC COSINON-W 35mm f/2.8 gives a first impression of a well thought of design and a reliable manufacturing quality.

And now to some pictures.

Lens(es) Wide Open

As said, I have made a side-by-side comparison - using my Pentax K200D for both lenses - resulting in more or less identical sets of scenes such as this example:


Cosinon-W images here and below are shown to the left. Images to the right are SMC Pentax-(K) images.

What I have noted is that - at least to my untrained eye and after some pixel peeping - is that the Cosinon actually provides a decent uniform image quality from corner to corner. This is far from trivial with these vintage lenses when used wide open. One should of course keep jn mind that this test has been made with an APS-C sensor and that the situation might be different with a full frame lens or film. Nonetheless, for my uses this is an interesting and promising result.

In the following, for the sake of clarity in detail, I just show identical crops from full-size scenes as the one shown above.




Comparison of Cosinon-W, (left) and SMC Pentax-K, (right) images at full aperture..

Judge for yourself how the two lenses compare. I actually find the Cosina COSINON-W 35mm f/2.8 surprisingly good on this wide-open comparison with the SMC Pentax K 35mm f/3.5.

Lens(es) Fully stopped down

Just a few shuts using flash to get a preliminary idea about lens performance when fully stopped down to f/22


Indications are, that the Cosinon-W will be fully usefull over the entire aperture range. More test images to follow....

A few sample images

Finally just a few un-cropped samples at various apertures and distances to get a general impression of the Cosinon-W performance in practise. Again, more sample images are to follow.

Concluding remarks (as for now).

In my search for information and other users' experiences with this lens, I have found close to nothing ( with the exeption of this page ). Cursory searches on e-Bay also have given no indication of abundances or value in contrast to the similar Cosina COSINON-W 28mm f/2.8 that appears to be more abundant.

However, with the results above, I have to conclude that I have treated this lens unfairly, having let it been idle for so long. 35 mm focal length may not be the most desirable for a contemporary APS-C camera; still, the image quality and the reasonably fast aperture for a lens of this kind ensures, that I won't keep it totally idle any longer!

Amongst others, astrophotography is waiting for it - I have already made star tests that convince me that this modest and "unknown" lens is ALSO pleasantly free of aberrations such as coma and chromatic aberration.


Copyright 2011  - Steen G. Bruun