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Pentax 25mm f/1.4 C-mount seems to be very popular lately...

V

Vivek

Guest
Hey Vivek,
Which c mount adapter for cosmicar 25mm f1.3 (v2513) no modify, I use adapter from http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=370273896882&ssPageName=STRK:MEWNX:IT

but it must be modified this len. :cry::cry:

Thx.
snaf,

I use one of the c-mount adapters. Currently, it is the first c-mount adapter that ever appeared- made by Wolfgang Rabe. Others should work once the lens flange is trimmed a bit. I used a key file (the lens flange is brass, soft metal and hence it is easy to file). It took about 35mins or so. Others have done it successfully as well.

I believe the lens in question is a Computar TV 25/1.3 and no Cosmicar.

Also, lens is the proper spelling for a single objective. Lenses- is plural.

Good luck! Have fun!
 

laptoprob

New member
Just received the Cosmicar/Pentax 25/1,4. It is so small! Shorter than a 35mm canister, same diameter. No, the lens doesn't fit in a canister.
The aperture has eight blades.
I don't have a c-mount adapter yet, it is on the way.
 

laptoprob

New member
No caps, condition is good. Some dust inside, but overall clean.
Actually it will fit in some canisters if the rubber grip wouldn't stick out...
Filter size is 27mm.
 

Jonas

Active member
When buying it new you get caps. See post 27 above.
Now those caps are more or less meaningless: I replaced the front cap with a hood (sometimes this lens flares) and the rear cap with a C-mount adapter and a µ4/3 cap.

There are also small screws on the aperture and focusing rings making it possible to lock them (for CCTV use). They don't make us anything good so out they go. Then one can replace just one of these with a longer lock screw (I don't know the name of these, longer chromed things you can tighten or untighten using your fingers only) in effect working as a tap making it easier to handle the little lens.
 
T

turbo

Guest
Just got a Cosmicar 25mm f1.4, older version - 6 blades.
A few quick tests.

Full picture



Cosmicar - Center @f/1.4



Computer - Center @f1.3



Lumix 14-45 (~25mm) - Center @f4.8



Cosmicar - Corner



Computar - Corner




Lumix 14-45 (~25mm) - Corner




Cosmicar - Corner @f/8



Computar - Corner @f/8



Lumix 14-45 (~25mmm) - Corner @f/8




The centers are all similar in sharpness, less so in contrast.
The corners are where the real differences show up.

Can only post 10 pics, full frame for last shot in next post.
 

laptoprob

New member
First trial of the Pentax 25/1,4. No adapter yet, so handheld with a metal disc. I'm excited, no vignetting! No swirls either. Only the cateye-deformed circles, which seem to be native to fast lenses.
No mount means very difficult focusing. So out-of-focus tested, very nice!
 
A

Abbazz

Guest
Only the cateye-deformed circles, which seem to be native to fast lenses
In fact, they are native to fast lenses with insufficiently dimensioned front element -- it's optical vignetting.

I am quite surprised your Pentax doesn't exhibit dark corners. Are your pictures full size 4:3 captures?

Cheers!

Abbazz
 

laptoprob

New member
I set my GF1 to 2:3 ratio, but that difference is small. These pics are full size direct jpegs. The ring I used to handhold this lens in front of the camera has a recess of about 2,5mm, so that should be almost the same as a proper C-mount adapter.
About optical vignetting, I know this effect from many examples of fast lenses. To get rid of it, the front lens must be huge.
 
A

Abbazz

Guest
I set my GF1 to 2:3 ratio, but that difference is small. These pics are full size direct jpegs. The ring I used to handhold this lens in front of the camera has a recess of about 2,5mm, so that should be almost the same as a proper C-mount adapter.
The Pentax 25/1.4 exhibits black corners when used in 4:3 aspect ratio. Switching to 2:3 is enough to get rid of them.

About optical vignetting, I know this effect from many examples of fast lenses. To get rid of it, the front lens must be huge.
Huge, you are right. Just have a look at the size of the front element of the Sigma 50/1.4 -- which was specially designed to avoid optical vignetting -- compared to the Canon, Nikon and Pentax 50/1.4 lenses:


Photo credit: DPReview

Cheers!

Abbazz
 

laptoprob

New member
Ha! got the C-mount adapter today. Great! The 25/1,4 starts vignetting only at 5,6. So there is some room for stopping down.
I do want a hood for it though. But vignetting will probably start earlier. Grmbl.
 
Last edited:

f6cvalkyrie

Well-known member
I just ordered one, thanks for the link !

Rafael

Well, the lens took terribly long, but I finally got it yesterday :confused::confused:
I went for a walk with it today. The pictures came out as a complete surprise to me : this lens performs almost the same as my c-mount Bell&Howell 25/1.9

Same "ancient" look to the pics, same vignetting, same swirly bokeh.

Here's a few shots from today. I processed them in accordance with the "vintage" look they anyhow induce.











All G1 with Cosmicar/Pentax 25/1.4 @ 1.4

C U,
Rafael
 

woodmancy

Subscriber Member



Well, the lens took terribly long, but I finally got it yesterday :confused::confused:
I went for a walk with it today. The pictures came out as a complete surprise to me : this lens performs almost the same as my c-mount Bell&Howell 25/1.9

Same "ancient" look to the pics, same vignetting, same swirly bokeh.

Here's a few shots from today. I processed them in accordance with the "vintage" look they anyhow induce.


All G1 with Cosmicar/Pentax 25/1.4 @ 1.4

C U,
Rafael
Wonderful moody shots, Raf. I have this lens, need to do more with it

Keith
 

f6cvalkyrie

Well-known member
Thanks, Keith.
This seems to be a very moody lens :D:D

Here's two more shots with it, wide open, and a little PP done


(in the dark forest)



(steep hill)

CU,
Rafael
 
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