COSMICAR / PENTAX TV ZOOM LENS 8-48mm 1:1.0

sure, with the GH2 ETC it has great potential for many applications depending on your definition of pro though. I have the Pentax 12.5-75mm 1.8 and it's sharp as a tack. Great for music video's, experimental imagery, stylized documentary etc. It's not a cheap lens and yet to see anyone post imagery from that exact lens to date anywere.
 
alfred said:
Very fast lens! But sharp enough to be professional usable? Any experiences?
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Keep in mind you can't use it with the c-mount adaptors, because the rear barrel is too wide for the adaptor... Months ago I adapted this zoom to a M4/3 mount. Was a big nightmare to collimate it properly!! With crucial micro work in the rear parts of the lens with a lathe machine...
This is really sharp in all focals, even at f1.0 f.1.2 at 48mm) and moving the zoom barrel is very smooth.
For me the question is that the ETC mode (the only way to use it in the GH2) is clearly less sharp than the full mode.
All the best.
 
lluis said:
Keep in mind you can't use it with the c-mount adaptors, because the rear barrel is too wide for the adaptor... Months ago I adapted this zoom to a M4/3 mount. Was a big nightmare to collimate it properly!! With crucial micro work in the rear parts of the lens with a lathe machine
This is really sharp in all focals, even at f1.0 f.1.2 at 48mm) and moving the zoom barrel is very smooth.
For me the question is that the ETC mode (the only way to use it in the GH2) is clearly less sharp than the full mode.
All the best.
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Yes, I want to use the lens only in the ETC mode. I think pictures in this mode are mostly less sharp, since the plurality of used lenses are 4/3 lenses, which have an optimized solution for 4/3 and not for ETC. So I expect good quality from the lens, since it is a generic 2/3 lens. Of course ETC doesn´t go as fast as 4/3 . Higher Iso makes noise and pictures less sharp.

How did you collimate the lens. Filing off the edge of the outer ring on the backside? I have a friend, who has lathe machine, too. We managed to fit a cosmicar 1.4 /25 sucessfully screwing off the backside ring before bhehinning with mechanical treatment of the ring

Thanks for your information about the sharpeness at 1.0. :happy:

How much did you pay? By ebay? Thanks.
 
biginvegas said:
sure, with the GH2 ETC it has great potential for many applications depending on your definition of pro though. I have the Pentax 12.5-75mm 1.8 and it's sharp as a tack. Great for music video's, experimental imagery, stylized documentary etc. It's not a cheap lens and yet to see anyone post imagery from that exact lens to date anywere.
Click to expand...

Pentax has fine lenses. I have a lot of old K-lenses. But my 1.4. 50mm (35mm cam lens) is not very sharp with full aperture. So I don´t use it with bthis iris, I am a little bit skeptical about the aperture of 1.0 by a zoom specially. I want to know, which way is better: your 12,5-75 or the 8-48mm 1.0. I think the last one could be a fine lense for nihgt shots. But no matter, if the lens wouldn´t be sharp.:shocked:
 
Alfred: I paid about 80 british pounds in ebay.co.uk. The lens is generic for 1/2" (not 2/3"). I have many experience in adapting lens and cameras (I come from movie equipment...) and I can tell you that to adapt this lens to M4/3 isn't an easy job... It's necessary to separate and machining the rear lens parts (not only the c-mount). Collimate a zoom f1.0 (with a 8mm wide focal) is a precision work of 0.001 millimeter in all its parts...
Only the best.
 
lluis said:
Alfred: I paid about 80 british pounds in ebay.co.uk. The lens is generic for 1/2" (not 2/3"). I have many experience in adapting lens and cameras (I come from movie equipment...) and I can tell you that to adapt this lens to M4/3 isn't an easy job... It's necessary to separate and machining the rear lens parts (not only the c-mount). Collimate a zoom f1.0 (with a 8mm wide focal) is a precision work of 0.001 millimeter in all its parts...
Only the best.
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hmmm ... we have only mounted off the chrome backside ring, which is about 3mm too wide for the c-mount-adapter. Then we filed off the edges of this chrome ring, so that the plain backside of the ring got contact with the adapter and screwed the ring to the lens and it worked perfectly. (We have not changed the original focal distance of the lens in any way.). The lens doesn´t work with each adapter, since there are a lot of c-mount adapters on the market, which don´t fullfill the specification of 4/3 adapters concerning the focal length. Best results I got with ciecios adapters. They are very exactly made.

How did you collimade the lense? Are there blades only 0.001 millimeter thick or how else did you manage this? Is there a special screw in the lens for collimation?:undecided
 
are we talking about this Pentax lens?
http://www.bhphotovideo.com/c/product/341297-REG/Pentax_C60812_C60812_8mm_to_48mm.html
the 1/2" 8-48mm 1.1 it should fit to most c -m4/3 adapters.
I have the Adorama Kipon that fits the 12.5-75mm:
http://www.bhphotovideo.com/c/product/341305-REG/Pentax_C31204TH_C31204_12_5mm_to_75mm.html
and a few Pentax CCTV that fit just fine. That it's the 1/2" CCTV I'm not sure makes a difference. If anyone knows definitive not I'm keen to hear. I have cheaper 1/2" CCTv that fit fine.

I'm going to pull the trigger and buy the 8-48mm in the next month so will let you know. It's always a risky buy as these lenses are obviously not made for the GH1/2 etc and it's pricey. The aesthetic it brings suits the work I do so I have to keep experimenting.

These Pentax lenses are not related at all but by name to K series. Not close to the still lens quality but great for their application to the Gh2 ETC.

The 12.5-74mm has very hard loud stops 1.8-22 so had it cheaply declicked by a local camera tech for 20 bucks.

The 12-75 also has a ring inside the end of the barrel with 3 screw like markers that can be seen inside the frame with lens wide open. I had those removed as well.

The interesting thing about some of these lenses is that they are held together by screws (size of spectacle frame) and can be taken apart very easily and modified for experimenting. I took apart the 25mm 1.4 pentax and reasembled it in 10 minutes. I was looking for a filter/coating inside that was giving the lens blue sun flares.
 
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You CAN NOT fit this Pentax 8-48mm zoom in any c-mount/M43 adapter. This lens is bigger than the 12.5-75mm. The rear c-mount barrel has 47mm in outside diameter, which is about 10mm wider than the top limit in these adapters.
 
pentax zooms.jpg

http://www.rmassa.com/manu/cosmicar.htm

Looking at diagrams of the two lenses. The rear c mounts do show the difference in the two. The rear extended piece with the 18.7mm marking... is that the offending chrome end that needs to be "removed"? The diagram of the 12-75 shows the c mount at 3.5mm that fits my kipon perfectly. The 18-48mm has two measurements for the c mount 3.5mm and 3.8mm for the extension.

Luis, can show you show me a pic of the rear of the 8-48mm lens as you described?

Thanks
 
http://imageshack.us/photo/my-images/593/foto006i.jpg/
The only way to adapt it is to remove all the c-mount brass unit and machining a Leica m39/M43 adaptor... Also open the rear part of the lens and machining it... All calibrated with 0,01/0,001mm tolerances and fixed with special lateral screws... Collimade properly this lens was (repeat) a big nightmare!! Don't try it if you don't know what are you doing.
 
lluis said:
You CAN NOT fit this Pentax 8-48mm zoom in any c-mount/M43 adapter. This lens is bigger than the 12.5-75mm. The rear c-mount barrel has 47mm in outside diameter, which is about 10mm wider than the top limit in these adapters.
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Thanks very much for this information and your warning. 47mm is too much for my lens adaptation experiences on m 4/3 adapters. You safed me doing a bad buy!:kiss:
 
any samples with this lens? I suppose the vignetting will be terrible and only viable with ETC mode?
 
mcbob said:
How about using this (or any other wide c-mount) with a 1.5-2x c-mount extender?
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I don't know what to make of c-mount extenders... I presume the fact that anything c-mount doesn't cover the entire m4/3 sensor, the c-mount extender may vignette anyway making it pointless to use it? Correct me if I'm wrong since I've never used one.
 
Does anyone know of a place to send your C-mount lenses to get them modified? And how much it costs?

Also, I assume modifying the c-mount lens will make them harder or impossible to attach to regular 16 mm film cameras?

thanks
 
ed_lee83 said:
I don't know what to make of c-mount extenders... I presume the fact that anything c-mount doesn't cover the entire m4/3 sensor, the c-mount extender may vignette anyway making it pointless to use it? Correct me if I'm wrong since I've never used one.
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I have a 2x C-mount extender (for 1/2" sensor), and 2 c-mount lenses - a Kern-Switar 16/1.8 (for 16mm) and a Tamron CCTV 4-12/1.2 (for 1/2"). Simple news, the extender eliminates the vignetting (even without ETC) with both lenses, but you lose two full stops. With the 4-12, it also prevents the lens from going full wide (the rear element of the lens obstructs the front element of the extender) - max wide angle is about ~6mm, which is still not bad.

Now, the 4-12 is anything BUT a video lens, as it's the exact opposite of parfocal, is small and fiddly to use, and quality is kinda feh with a square bokeh - but it's OK to use for effects or just to have something to get a wide shot in low light.

Now, a 1.5x extender should lose a full stop of light, but if you're starting from f1.0... well, you could really do worse than an effective parfocal 24-144/1.4, couldn't you?

I'll report back after some fiddling...
 
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