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Cosmicar TV 4.8mm F/1.8
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PostPosted: Wed Jan 04, 2012 9:52 pm    Post subject: Cosmicar TV 4.8mm F/1.8 Reply with quote
This is a fun little toy. I got it from one of those anti-theft cameras that were in use in the 80's - you know the kind that are shaped like a flat rectangular whiskey flask? Using the 2x digital zoom on the GH1 I get perfect coverage with it. It's very sharp in the center wide open at f/1.8 and I do mean ONLY the very center! The smeary blurs proceed to get worse linearly as we go out toward the edges of the frame from there. Luckily by the time it's dialed down to f/5.6 or f/6.3 all of that is gone but for only the extreme edges - and by f/8 even those are cleared up. The lens has no focus ring at all. To get it to seat perfectly on the c-mount adapter at exactly the optimal registration distance I needed to create a gasket exactly the thickness of 1 piece of notebook paper - easily done and all that practice cutting folded paper in the 1st grade really paid off here! Here's an entire set shot with this lens set at f/5.6. A few of these are two exposure tone-mapped images where the DR was too great for my little GH1. The AOV is very close to 180˚ and I had kind of a hard time keeping my shoes out of the frame on most of these - especially the ones taken in portrait orientation. All of them were shot in fine JPeg with the digital zoom set to 2x - just so I didn't have to hand crop them even though all such images can be cropped all at once with just a mouse drag and a click.

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!-Enjoy


PostPosted: Thu Jan 05, 2012 7:31 pm    Post subject: Reply with quote
Hey, I think we know each other from the MacRumors forum?

My issue with this lens would be the vignetting, and it probably is not delivering the resolution
that even the cropped portion of the sensor would handle. I think it's a 'megapixel' lens. Even with
vignetting, I can see how it would be a very fun toy to have.

It's really cool that we can now experiment with these lenses with our EVIL cameras. Because of the
protruding rear element, this lens and the Cosmicar 8.5mm have previously been unlikely candidates for use on native c-mount Super8mm and 16mm cameras. Typically the rear element would contact the mask just beyond the c-mount of the camera.

It's nice to see the lens for it's own resolving power. Did you adjust curves/saturation much?


PostPosted: Thu Jan 05, 2012 11:45 pm    Post subject: Reply with quote
ekoe wrote:
Hey, I think we know each other from the MacRumors forum?


Yeah, could be. I was active there about 2 years ago until the mods proved themselves idiots by trying to control political opinion in the political sub-forum. Now they get no more clicks from me. Smile

Quote:
My issue with this lens would be the vignetting, and it probably is not delivering the resolution
that even the cropped portion of the sensor would handle. I think it's a 'megapixel' lens. Even with
vignetting, I can see how it would be a very fun toy to have.

It's really cool that we can now experiment with these lenses with our EVIL cameras. Because of the
protruding rear element, this lens and the Cosmicar 8.5mm have previously been unlikely candidates for use on native c-mount Super8mm and 16mm cameras. Typically the rear element would contact the mask just beyond the c-mount of the camera.

It's nice to see the lens for it's own resolving power. Did you adjust curves/saturation much?


Not too much no. But I did some for sure... Sometimes even reducing saturation. in-camera jpeg and 2x digital zoom is a terrible combination in the GH1. UG!

About 5mm AOV coverage can be pretty creative in the hands of someone (else) who knows how to use it tho.

I think the fact that these were shot with 2x digital zoom and in camera-jpeg kinda destroyed most of the detail - and my processing to resurrect that probably just made it worse. :p

The next time I take this lens out I'll shoot RAW and crop them myself and process them normally.

Here's what the lens looks like shot without digital zoom and in RAW capture mode - again at f/5.6. I did cut off the sides some to save a little bandwidth and storage tho. This is just a shot of my storage room... Taken about 4 inches away from that foreground towel. Also keen in mind that from f/8 to f/11 things are improved yet even more. F/5.6-ish is just the point at which the corners sharpen up enough to not be a detraction:

[c]




And a 100% crop thereof:

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I think not bad for a 4.8mm $5 lens. Smile Good enough for web-sized images IMO anyway. I think good enough for 8x10 prints too if they're viewed from 1.5m or more away.


PostPosted: Sat Jan 07, 2012 12:05 am    Post subject: Reply with quote
Here's a shot of my friend taken a little less than one inch from his face at f/11. I used the GH1's flash with some tish over it to diffuse it a little. I think you can see the tish in the reflection of the monitor glass behind my little buddy there - dang glossy surfaced monitors!




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After Cropping







Before Cropping
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PostPosted: Sat Jan 07, 2012 4:08 pm    Post subject: Reply with quote
Nice results! I think it would perform nicely on the Pentax Q with its tiny sensor.


PostPosted: Sat Jan 07, 2012 8:09 pm    Post subject: Reply with quote
Yeah... or the J1 V1 maybe too...
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