Monday, November 29, 2010

Cosmicar 12.5mm f1.4 Television Lens

Micro 4/3 users are usually at a disadvantage when it comes to manual focus wide angle lenses, due to the 2x crop factor.  Any lens mounted on a Micro 4/3 camera, its focal length will be multiplied by 2.  So, even for a modest 28mm equivalent wide angle, you would need a 14mm lens in 35mm format.  Well, we all know how much one has to pay for a manual focus 14mm lens, regardless who makes it.

One alternative to normal 35mm format lens, is C-Mount Television lens.  These lenses are usually pretty cheap, but they also have very small image circle, not to mention the normally abysmal resolving power.  You can usually find very wide angle C-Mount TV lenses as wide a 6mm.  Unfortunately, all you would usually get is a small circle of an image with a huge black border.  In other words, not really usable.  There are some that covers  a larger sensor, such as the 1 inch sensors.  You can tell by the size of the lens.  If it's really small, it would have a rather small imaging circle.  A friend of mine showed me a trick to check the approximate image circle of a lens.  Find a light source, and use the lens to form the clear image on your palm.  The size of the image gives you some idea how much coverage the lens can provide.

I came across a Cosmicar 12.5mm f1.4 TV lens.  Cosmicar is a division of Pentax that manufacture close circuit TV lenses.  The size of this lens is almost the same as the Angenieux 70mm f2.5.  It's very fast for such a wide angle lens with a maximum aperture of f1.2.  Mounted on the G1, the equivalent focal length is 25mm.  This is wide enough for most occasions.  BUT, you don't get the whole image, sad to say.  This lens would cover a one inch sensor, but not enough to cover the Micro 4/3 sensor, hence its heavy vignetting.  As with most wide angle TV/Cine lenses, the edges are blurry.  This particular lens would still give you usable image if cropped at the long edges.

In terms of image quality, contrast is low wide open, with a soft glow, but still quite sharp.  From f2.8, center sharpness is actually quite respectable with markedly improved contrast.  Resolving power seems low, as expected from a TV lens.  Not too crazy about the colour that comes out of this lens either.  The colour seems washed out.  Minimum focusing distance is 0.3 meters, or about 12 inches.

The 14-45mm kit lens is still light years better than this cosmicar lens in terms of sharpness, contrast and colour saturation, but it does free you from Photoshopping your own vignettes.  In some situations, this lens gives you somewhat unique characteristics not possible with the kit lens, especially in dim lighting condition where you can take pictures at f1.4. It's kind of fun to play with, as long as you can get it cheap.

Wide Open at f1.4 -- note the soft glow effect and heavy vignetting

Fence -- Aperture is around f4.  Note drab colour.

9 comments:

  1. was pretty happy with mine ... my best (most liked) shot with it is this one:

    http://farm4.static.flickr.com/3499/4001914010_0905e413c1_z.jpg?zz=1

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  2. Wow, how cute is that!?! Nice one.

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  3. I purchased mine for $50 but I'm having a problem with it.

    The C mount adapter I have (which I use with a 6mm and 25mm CCTV lenses) won't allow the Cosmicar 12.5 to mount.

    Which adapter do you guys use? Mine is a Fotasy. Made/shipped from China of course.

    Cheers,

    Josef

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  4. @Josef: I use a very cheap c-mount adapter -- the JR adapter. When looking for a c-mount adapter, try to find one that has a large opening. Some have inner threads (42mm and 55mm) which may limit the lens diameter slightly. Good luck.

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  5. JR adapter? Could u please give me a link to buy it? Because I also find the normal c-mount adapter can't work. Great Thanks!

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  6. http://item.taobao.com/item.htm?spm=a230r.1.14.34.cp2FMN&id=12441884745&initiative_new=1

    Is this the same adapter as yours?

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  7. Someone gave me an itteh bitteh cosmicar lens and I'm not exactly sure what it mounts onto! Any clues are appreciated :-)

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    Replies
    1. It's most likely a c-mount lens. You can use it on CCTV cameras, or Micro 4/3 or even NEX cameras with an adapter.

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  8. There are several different models of the Cosmicar 12.5mm f/1.4 lens. The newer models have a 40.5mm rear mount end diameter, which is too large to fit any of the C-Mount to MFT adapters currently on the market, at least the ones I tried (5 different ones.) This means the lens will not fit all the way into the adapter, requires modification for infinity focus. I was able to modify mine for infinity, I can talk about it more if anyone is interested.

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