follow up on computar 12.5/1.4

[rbelyell]

recently dave (farside) posted this lens for sale on a surplus site for $25usd. i grabbed one for my ep1 and said i would post some pix when it arrived. well, here they are!

basically, this performs as a macro lens where one has to get very close to the subject. although it has 'infinity' focus, you will see from below it really doesnt function properly in that mode--i dont know if this particular lens is malfunctioning or that's the way it's supposed to be.

however, at very close range it really is pretty cool! the color rendition is kind of stunning really, and i think the level of detail is more than can be expected of a $25 lens.

it does have a fair amount of vignetting, as to be expected from 12.5mm cine lens, but not as much as expected--in fact if you shoot 1:1 it almost crops the whole vignetting out.

let me know what you guys think. as always PLEASE CLICK ON EACH PHOTO FOR BEST RESOLUTION:




this is what 'infinity' focus looks like:



i think i will enjoy this lens; thanks dave!

[no-X]

The first two samples have nice color and in-focus sharpness seems to be fine. The last example isn't good. Seems to me the lens doesn't hit infinity or one of the glass elements is loosy...

[rbelyell]

i dont know if anyone read my post, but i did say that 'infinity' focus did not work on this lens. the posted picture was merely to illustrate that fact.

klaus, im not sure if you are referring to infinity focus, but the first two are very nice samples to me on my screen. the lens, like a lot of cine lenses, has some unusual properties and interesting DOF, its not a regular lens and i am judging it, like other cine lenses i have seen, by different standard. i think there is a place for 'swirly' focus, mixed bokeh, its just different. but i would be very interested to hear an expanded version of your thoughts!

[Laurence]

I think the colors are really great. I can see the usefulness / fun to be
had with this lens. It looks like it would be good in a situation where
you wanted an exceptionally short depth of field.

[rbelyell]

thanks lawrence. yeah, thats what im thinking. to be honest, i did expect to be able to use longer focus lengths, but as i said, it may be an imperfection or the lens design, but thats not possible. for $25 it can yield some funky macro work.

[apicius9]

Do you have a picture of the lens itself posted somewhere? I think my Computar is a 12.5/1.3 but there may just be different versions out there. In any case, my Computar reaches infinity with a little trick: Under the rubber band of the focus ring there is a small screw that limits the focus range. If you take that screw out, you can focus further and the lens reaches infinity. You just have to be a little bit careful that you don't force the focus ring too far but you will notice the resistance. Works great with both my Computars, the 12.5mm and the 25mm, an the 12.5mm has minimal vignetting in the 1:1 format.

Stefan

[rbelyell]

stefan that is very nice of you to share that with me.

when you say 'under the rubber band', do you mean that i should remove the band from the lens body--because i do not see the screw anywhere with the band on...

[apicius9]

Yep, you can try to lift the rubber band and see if you can spot the screw or remove the band (mine only had a few small glue points) and put it back in place later, fix it with a few drops of superglue if you find it necessary (I didn't).

Stefan

[rbelyell]

stefan, thank you so much! i did as you said and the lens does indeed now focus closer to infinity--not totally there, but much closer. interestingly i wonder if you have the same issue i do, which is that at 1.3 aperture the infinity focus is totally blurry, but stopped down to f 16 it becomes much sharper. do you think there is something wrong w my lens, or do you have that situation as well?

[apicius9]

I remember something like that but not what lens it was, will have to try it out when I get a chance. Probably not today, looks like a looong day int he office...

Stefan

[wilson.c]

I remember I read somewhere in this forum that some of these TV lenses flange in the rear is too big and needs to be filed down to properly seat with the C-mount adapter for Infinity focus. It needs to be something like 1 or 2mm smaller in the back to get the clearance in the adapter. Have you checked that?

[rbelyell]

thanks wilson. to be honest, im not sure about that. i have a couple of lenses--most notably the tak 50/1.4, that i can feel when focusing tightens in certain adapters. with this lens i dont feel any tightening while focusing. taking out the screw helped a lot, but maybe you are correct. how would i know for sure?