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Help on an Isconar 100mm f/4.5
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PostPosted: Fri Sep 11, 2020 5:45 am    Post subject: Help on an Isconar 100mm f/4.5 Reply with quote

Just got this little lens. Found the aperture ring seems to be able to move around the barrel without stop. If keeping turning, occassionally, I heard a click and it seems engaging something and the apertuer ring can have two mechanical stops (feels like f/4.5 and f/22). However, the blades never show up. I guess it is faulty correct? Just would like to have a confirmation and anyone have similar issues with this lens? Thank you very much!


PostPosted: Fri Sep 11, 2020 8:05 pm    Post subject: Re: Help on an Isconar 100mm f/4.5 Reply with quote

vivaldibow wrote:
Just got this little lens. Found the aperture ring seems to be able to move around the barrel without stop. If keeping turning, occassionally, I heard a click and it seems engaging something and the apertu ring can have two mechanical stops (feels like f/4.5 and f/22). However, the blades never show up. I guess it is faulty correct? Just would like to have a confirmation and anyone have similar issues with this lens? Thank you very much!


I just finished tearing apart two of these to rebuild into one really nice one. The construction is extremely simple. The aperture itself is a bit fragile and if it breaks...well, I haven't found a way to fix it. There's a thin metal tab that fits into a groove inside the aperture ring, and if that's broken off you're out of luck unless you can figure out how to make a new one. If the blades are deformed it's even trickier because the whole mechanism is held in place by metal that is simply pinched over the top (that may not make sense, but you'll see what I mean if you open it up).

If you want to take it apart, I can certainly help. Unlike most lenses there's really nothing you can mess up by putting it back together the wrong way, since infinity focus can be calibrated by eye as you reconstruct it - especially easy if you've got a camera with focus peaking.

Things to watch out for:

1) Don't strip the three little screws in the focus ring. That would be bad! Smile

2) The entire lower barrel and the mount are one single piece. If you look carefully inside from the mount end, you'll see a single screw that has been painted black. This screw clamps the barrel in the correct position, so take it out before you unscrew the barrel.

3) Before you take the aperture ring off, be aware that underneath it are two ball bearings supported by two tiny springs in holes. These are extremely easy to lose if you're not careful.

4) The barrel is completely featureless with no markings of any kind, so when you screw it back on how do you know you've returned it to the correct position? I screw it on all the way, then put an adapter on the end and unscrew it until the focus and aperture indicator line is on top - aligned with the top of the adapter, which typically has a logo of some kind. Then put the black screw back in place to clamp it in position.

Hope this helps. If you have any more questions, feel free to ask.


PostPosted: Sat Sep 12, 2020 5:00 am    Post subject: Reply with quote

@KEO, appreciate the details. All noted. Will check back when I get a chance to fix this one. Have so many that need repair.Smile


PostPosted: Sat Sep 12, 2020 7:06 pm    Post subject: Reply with quote

vivaldibow wrote:
@KEO, appreciate the details. All noted. Will check back when I get a chance to fix this one. Have so many that need repair.Smile


Good luck! One more interesting item: as far as I can tell, this lens and the Westar 100 4.5 are exactly the same except for the font on the aperture ring (the Isconar is more elegant IMO). The parts are interchangeable.

I've seen junkers pop up on ebay for $10, so getting extra parts is also possible.


PostPosted: Sun Sep 13, 2020 3:57 am    Post subject: Reply with quote

KEO wrote:
vivaldibow wrote:
@KEO, appreciate the details. All noted. Will check back when I get a chance to fix this one. Have so many that need repair.Smile


Good luck! One more interesting item: as far as I can tell, this lens and the Westar 100 4.5 are exactly the same except for the font on the aperture ring (the Isconar is more elegant IMO). The parts are interchangeable.

I've seen junkers pop up on ebay for $10, so getting extra parts is also possible.


Good to know. I did notice Isco sometimes has Western or similar on the name plate. Interestingly, my first Isco lens is a movie projection lens, a pretty modern one.