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Showcase Cosmicar (Pentax) 50mm f1.4

Discussion in 'Adapted Lens Sample Image Showcase' started by gnarlydog australia, Jul 6, 2016.

  1. gnarlydog australia

    gnarlydog australia Mu-43 Top Veteran

    975
    Feb 23, 2015
    Brisbane, Australia
    Damiano Visocnik
    I was surprised to not see the Cosmicar 50mm f1.4 lens in this forum and now I know why: It's not so easy to adapt to Micro 4/3.
    The rear of the lens is too wide to mount on a typical C-mount adapter so a straight screw-on is not possible. The lens could be used as close-up/macro with a little spacer ring (5mm) but I wanted to use that lens at full potential.
    There must be a way to use it on M43...

    I pulled the rear of the lens off (the silver bit) by loosening the 3 grub screws. The back came off easily and nothing sprung out of the lens (the f-stops are not indexed so no little spring and ball that often gets lost).

    28127060795_8946affab6_c. Cosmicar rear screws by gnarlydog, on Flickr

    With the rear of the lens detached I was able to almost form an image at infinity with the C-mount adapter on the body of the camera.
    I managed to get closer again by adjusting the helicoid stop on the barrel of the lens.
    I lifted the rubber focus band and loosened the 3 tiny screws. I pushed (turned/screw) the optical block as far back (close to the sensor) as possible. I was getting very close but no cigar, yet.:mad:

    I thought infinity could be reached if I shaved a bit of metal, either from the lens or the C-mount.
    I went for the C-mount since it costs only $3 instead of altering a lens that I was not sure was going to work...

    27846048060_4baf9c5ba6_c. C-mount shaved_c by gnarlydog, on Flickr

    With a Dremel and a metal cut-off wheel I recessed about 1mm into the edge of the flange to let the lens sit closer to the sensor. One hour later I had infinity focus :yahoo:

    Then I needed to create a spacer to keep the aperture ring in place and slightly spring loaded.
    I needed a ring that was about 48mm outside diameter and 43mm inside diameter.
    Luck has it that a step-down ring 46mm-43mm was fitting just perfectly!
    I cut the thread off and reduce the height to 3mm.

    28126757355_18cf7f5942_c. Cosmicar modification to rear_c by gnarlydog, on Flickr

    I then used JB Weld epoxy glue to secure the (naked) rear of the Cosmicar onto the C-mount, while placing the spacer ring and the little spring washer in between. The spring washer offers resistance to the click-less aperture ring, without it the aperture moves too easily.

    28092274276_df4e875dbc_c. Spacer ring_c by gnarlydog, on Flickr

    I waited 20 minutes and checked if the lens was focusing at infinity. It was, just slightly over. I went back to my 3 tiny screws under the rubber band and adjusted the infinity stop on the barrel to match infinity focus: perfect.

    27511811384_58ef439f6f_c. Detail of mounting_c by gnarlydog, on Flickr

    Quick tests reveal this being a potentially brilliant lens with smooth bokeh, sharp and on par (if not better) than my SMC Takumar 50mm f1.4, just half the size! :thumbsup:

    28093302936_01198bd725_b. Cosmicar vs Takumar_c by gnarlydog, on Flickr

    Cosmicar 167gr. , Takumar 307gr. (including adapter)

    Sample images coming soon...
     
    Last edited: Sep 4, 2016
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  2. gnarlydog australia

    gnarlydog australia Mu-43 Top Veteran

    975
    Feb 23, 2015
    Brisbane, Australia
    Damiano Visocnik
    bokeh test at closest focusing range of 1 meter (approx. 3feet))
    all images were shot in .jpg and only adjusted for exposure (brightness/contrast). Click on image to see larger size
    wide open:
    27864703210_a39bf5c5dc_z. Cosmi_closest focus_c by gnarlydog, on Flickr

    at f2.5 (approx.)
    27530478314_6d420fe173_z. Cosmi_closest focus_2_c by gnarlydog, on Flickr

    at f5.6
    28067491921_07f3d6fca1_z. Cosmi_closest focus_3_c by gnarlydog, on Flickr

    The speckled highlights are rendered as "arrows" due to the 3-blade aperture. In most situations the bokeh renders smooth, the arrows only show up in strong highlights. A unique lens that is fun to use, consciously :)

    at f4 approx., no edit
    28047186572_3b46d16946_b. DV070724 by gnarlydog, on Flickr
     
    Last edited: Jul 7, 2016
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  3. gnarlydog australia

    gnarlydog australia Mu-43 Top Veteran

    975
    Feb 23, 2015
    Brisbane, Australia
    Damiano Visocnik
    Last edited: Jul 7, 2016
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  4. gnarlydog australia

    gnarlydog australia Mu-43 Top Veteran

    975
    Feb 23, 2015
    Brisbane, Australia
    Damiano Visocnik
    I have another 50mm in f1.4 aperture: SMC Takumar
    I took a few images of the same scene: here collated, cropped at 100% centre of image, no processing, compared to the Cosmicar

    28046069912_42ef522e2b_h. Cosmi vs Taku_c by gnarlydog, on Flickr
     
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  5. gnarlydog australia

    gnarlydog australia Mu-43 Top Veteran

    975
    Feb 23, 2015
    Brisbane, Australia
    Damiano Visocnik
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  6. Crdome

    Crdome Mu-43 Hall of Famer

    Sep 11, 2011
    West Central Indiana
    Chrome
    Impressive accomplishment!
     
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  7. the_photonerd

    the_photonerd Mu-43 Rookie

    14
    Jul 8, 2016
    Germany
    Christian
    OMG, I get this lent together with the Cosmicar 75mm. Looks a little complicated. Do you think it is possible to reduce the Diameter of the metallic tube (be turning) so it will fit in the standard C-Mount adapter?
     
  8. gnarlydog australia

    gnarlydog australia Mu-43 Top Veteran

    975
    Feb 23, 2015
    Brisbane, Australia
    Damiano Visocnik
    I believe the lens' rear could be machined on a lathe to reduce the diameter and make it fit on a standard C-mount adapter, but I don't have a lathe so I can't tell for sure.
    I found it easier to simply remove the rear bit and glue it to the adapter: something I could do without specialized tools.
     
    Last edited: Sep 4, 2016
  9. gnarlydog australia

    gnarlydog australia Mu-43 Top Veteran

    975
    Feb 23, 2015
    Brisbane, Australia
    Damiano Visocnik
    now that I have used the lens for a bit longer I have a better understanding of its weaknesses and strengths.
    I am still impressed but its small size and usability, easy to focus and the weird 3-blade aperture creates unusual bokeh.
    The lens has a really nice "flavor" for portrait and closer up subjects but starts to loose sharpness when focused at infinity.
    The centre remains sharp but the edges are too soft for my liking as a "landscape" lens.
    I finally discovered that it was not me or the camera that could not produce a pin-sharp image with people at 30 feet or so: the lens just can't render very well far away.
    Yes, the overall image is OK but once magnified to 200% I can say it ain't no Zuiko...

    I think the lens excels at closer subjects, portrait (head and shoulder)
    Some more samples here:

    29106374896_a3dbc43f94_b. Lucia on Cosmi_c by gnarlydog, on Flickr

    28876108110_e0967cb25f_b. EmmaD_1_c by gnarlydog, on Flickr
     
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  10. stratokaster

    stratokaster Mu-43 All-Pro

    Jan 4, 2011
    Kyiv, Ukraine
    Pavel
    Impressive. I really like the swirly bokeh.
     
    Last edited: Aug 29, 2016
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  11. gnarlydog australia

    gnarlydog australia Mu-43 Top Veteran

    975
    Feb 23, 2015
    Brisbane, Australia
    Damiano Visocnik
    this is what this lens does best for me: mid-field subject with blurry (but not creamy) background out of focus

    29359429661_e80f7ba055_b. Alone_c by gnarlydog, on Flickr
     
    Last edited: Sep 4, 2016
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  12. gnarlydog australia

    gnarlydog australia Mu-43 Top Veteran

    975
    Feb 23, 2015
    Brisbane, Australia
    Damiano Visocnik
    color are also very nice but somehow it seems that they seem to slightly change (at least in the viewfinder) as I stop down the lens
    here wide open

    28894458783_d26fc50cc3_b. Scooter 125_c by gnarlydog, on Flickr
     
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  13. gnarlydog australia

    gnarlydog australia Mu-43 Top Veteran

    975
    Feb 23, 2015
    Brisbane, Australia
    Damiano Visocnik
    probably the Cosmicar 50mm f1.4 doesn't shine at infinity, even stopped down: the centre is sharp but the edges are smeared. I guess there is little vignetting but the image circle of this C-mount lens is evidently not enough for decent edged-to-edge sharp coverage on the Micro 4/3

    29673065602_01f06c1e38_b. Deep in the forest_c by gnarlydog, on Flickr
     
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