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Computar 25mm F/1.3
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PostPosted: Sun Jan 30, 2011 11:21 pm    Post subject: Computar 25mm F/1.3 Reply with quote
Had this lens a while but never tried it much because it wouldn't screw right into my c mount adapter so no infinity focus but I kept meaning to loosen the stop screw on the focus ring to see if I could turn the ring past infinity and it works!

This lens is pretty good imo, it's quite sharp wide open and at f/5.6-f/8 it's sharp quite far into the edges of the frame. Vignetting is moderate wide open and decreases as you stop down. The colour and contrast are great and the bokeh is nice and smooth and oof highlights looks cool when the lens is stopped down because there's only 3 aperture blades!

Last edited by fatdeeman on Wed Mar 26, 2014 6:16 pm; edited 1 time in total


PostPosted: Sun Jan 30, 2011 11:37 pm    Post subject: Reply with quote
performs nicely and the apparent vignetting disappears when stopping down. Good contrast and colors!


PostPosted: Mon Jan 31, 2011 6:23 am    Post subject: Reply with quote
congrats, nice lens!
Quote:
the bokeh is nice and smooth and oof highlights looks cool when the lens is stopped down because there's only 3 aperture blades!

can you show us some triblade bokeh with street lights


PostPosted: Mon Jan 31, 2011 8:04 am    Post subject: Reply with quote
poilu wrote:

can you show us some triblade bokeh with street lights


I completely forgot to get such shots yesterday but I will get some soon!


PostPosted: Mon Jan 31, 2011 6:23 pm    Post subject: Reply with quote
kds315* wrote:
performs nicely and the apparent vignetting disappears when stopping down. Good contrast and colors!


+1 very nice images!


PostPosted: Mon Jan 31, 2011 6:26 pm    Post subject: Reply with quote
Very nice indeed, do you have a picture of the lens? Very Happy


PostPosted: Mon Jan 31, 2011 7:03 pm    Post subject: Reply with quote
That's what µ4/3 is great for!


PostPosted: Mon Jan 31, 2011 8:36 pm    Post subject: Reply with quote
Nordentro wrote:
Very nice indeed, do you have a picture of the lens? Very Happy




The rubber focus grip is removed so I could loosen the focus stop screw which is aligned with the infinity mark in the photo.


PostPosted: Mon Jan 31, 2011 8:47 pm    Post subject: Reply with quote
It seems that the G1 is the perfect toy for those old lenses. The small sensor does have an advantage. Wink


PostPosted: Mon Jan 31, 2011 9:15 pm    Post subject: Reply with quote
LucisPictor wrote:
It seems that the G1 is the perfect toy for those old lenses. The small sensor does have an advantage. Wink

put them on your Nex and crop to 4:3, you will get the same pics Very Happy


PostPosted: Mon Jan 31, 2011 9:22 pm    Post subject: Reply with quote
LucisPictor wrote:
It seems that the G1 is the perfect toy for those old lenses. The small sensor does have an advantage. Wink


I just wish it was less noisy! At base iso it's great and the resolution is immense but it just doesn't cut it at higher iso like the NEX does.

I still can't work out why shots taken with the G1's kit lens come out less noisy than with adapted lenses, it obviously does some processing even with the raw files for some reason. iso 400 with an adapted lens is worse than iso 800 with the kit lens!

With the kit lens iso 800 is not bad on the G1 with the NEX iso 3200 is not bad with ANY lens!


PostPosted: Tue Feb 01, 2011 10:20 am    Post subject: Reply with quote
poilu wrote:
LucisPictor wrote:
It seems that the G1 is the perfect toy for those old lenses. The small sensor does have an advantage. Wink

put them on your Nex and crop to 4:3, you will get the same pics Very Happy

Laughing Yes, but not the same fun. Simliar to using a Tokina 12-24 at 12mm on a 5D and cropping then to APS (~19mm). Possible but nothing really thrilling.


PostPosted: Tue Feb 01, 2011 2:51 pm    Post subject: Reply with quote
wow what great and to me totally unexpected results with this inexpensive lens--congrats and thanks so much for sharing. maybe i made a mistake spending all that extra money on a tevidon! Very Happy


PostPosted: Thu Mar 10, 2011 10:43 pm    Post subject: Reply with quote
Hey guys, I am trying my local suppliers of CCTV systems for lenses, will these 25mm lenses cover the full frame with the minor vignetting shown in the images above?


PostPosted: Thu Mar 10, 2011 10:45 pm    Post subject: Reply with quote
muzzl3 wrote:
Hey guys, I am trying my local suppliers of CCTV systems for lenses, will these 25mm lenses cover the full frame with the minor vignetting shown in the images above?


Some of them cover it , some of them not.


PostPosted: Thu Mar 10, 2011 11:04 pm    Post subject: Reply with quote
Attila wrote:
Some of them cover it , some of them not.


Fair enough, I will see what I can find. Probably Computar or Cosmicar/Pentax. There's definitely a Cosmicar supplier near my city.

Just because shipping from overseas is so costly.

I have a few options I think:

23FM25SP Tamron 2/3" Machine Vision lens, Focal length 25mm ,F/1.4 with Lock for MegaPixel Cameras, 30.5mm filter thread

CF25HA-1 Fujinon lens, 25mm, 1" 1.5 Megapixel series (1/2"-1" CCD), F1.4~F22, C Mount, Manual (I,F)). Filter thread M49 x 0.75mm.

HF25SA-1 Fujinon lens, 25mm, 2/3" 5 MegaPixel series (1/3"-2/3" CCD), F1.4~F22, C Mount, Manual (I,F)


PostPosted: Thu Mar 10, 2011 11:48 pm    Post subject: Reply with quote
Without any knowledge about this lenses I vote for Fujinon. Good luck!


PostPosted: Fri Mar 11, 2011 3:31 am    Post subject: Reply with quote
Attila wrote:
Without any knowledge about this lenses I vote for Fujinon. Good luck!


Yeah RAD,
I spoke to the guys and sounds like they are happy to sell to me, pricing should be okay as they feel like a wholesale/supplier. On Monday they're guy will get back to me with a price.

As micro 4/3 is 22.5 mm diagonally, this is 0.89 inches.
1" lens would be cropped, assuming the same ccd distance, where as 2/3" lens would have the vignetting?
With this assumption a 25mm lens would be slightly more than 50mm (by how much I am not going to figure out) on a 2x crop, where as the 2/3" sensor would be more or less 50mm and may require cropping of the image itself - thus less pixels.

Perhaps I am over thinking these things Smile


PostPosted: Fri Mar 11, 2011 9:03 pm    Post subject: Reply with quote
rbelyell wrote:
wow what great and to me totally unexpected results with this inexpensive lens--congrats and thanks so much for sharing. maybe i made a mistake spending all that extra money on a tevidon! Very Happy

+1 (but no regrets with the Tevidon !)


PostPosted: Mon Mar 14, 2011 2:03 am    Post subject: Reply with quote
muzzl3 wrote:
CF25HA-1 Fujinon lens, 25mm, 1" 1.5 Megapixel series (1/2"-1" CCD), F1.4~F22, C Mount, Manual (I,F)). Filter thread M49 x 0.75mm.


The local supplier got back to me, at $290NZD for this lens I think I will keep looking for something cheaper on the second hand market Wink


PostPosted: Sat Jan 04, 2014 2:15 pm    Post subject: Reply with quote
Hello everyone. I bought this computar recently, it cost me cheap. I modified lens with removing focus limit screw to get infinity focus, but without that screw lens got focus overrun in both directions. It doesn't worry me so much, but nonetheless I keep searching more right decision of focus limiting in correct range, most near close up and infinity.
Here some samples from my MFT camera.

Close up, near minimum focus distance.


http://fotki.yandex.ru/users/anfyrt/view/737842/

http://fotki.yandex.ru/users/anfyrt/view/737841/

Last edited by anfyrt on Sat Jan 04, 2014 3:57 pm; edited 1 time in total


PostPosted: Sat Jan 04, 2014 2:25 pm    Post subject: Reply with quote
Some street snapshots with high ISO and low light.


http://fotki.yandex.ru/users/anfyrt/view/709551/

http://fotki.yandex.ru/users/anfyrt/view/709555/

http://fotki.yandex.ru/users/anfyrt/view/709563/

http://fotki.yandex.ru/users/anfyrt/view/709558/

I can say that this tiny tv lens is one one of my favourite mf-lenses. It is sharp straight from open wide aperture, it has nice colors and great bokeh and it looks great on my camera, it fits well on E-M5.

That's enough for now. Sorry for my ugly english. Bye.


PostPosted: Sat Jan 04, 2014 5:12 pm    Post subject: Reply with quote
Very nice Anfyrt and welcome to the forum Wink


PostPosted: Mon Aug 18, 2014 3:51 pm    Post subject: Computar 12.5mm f/1.3 MFT modification Reply with quote
I actually had just performed a Computar 12.5mm f/1.3 to MFT adaption (with infinity focus). I'll try to make this easier for you than it was for me. Wink

You need a C-mount to MFT adapter (which are usually less than 10-12 USD on amazon, less than that on eBay). There's a ridge which doesn't allow the back end of the lens to come close enough to the sensor for infinity focus, at least on the BMPCC. There are a bunch of people who tell you to dremel or file down the back of the lens, but you will most likely break the back lens mount if you do this too much. The trick is to pull out the screws on the back of the lens which connect the silver mount assembly, then manually unscrew the central lens assembly a few turns, which will bring it closer to your sensor. I can confirm that this modification (once re-assembled) does indeed produce working infinity focus for this lens, although I haven't checked to see whether the distance markings are still correct.

The C-mount adapter to MFT adapter I used was http://amzn.to/1oJL1bS

I also used a step up ring to give it a front filter mount of 58mm, which I could step up to my VND filter size ... http://amzn.to/1n1UIgl
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