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03-20-2012, 05:48 AM   #1
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I got my first vintage lens, does it not work or am I just stupid? (or both)

So I use to be a sony shooter and when I was looking for a new camera the ability to find cheap lens for Pentax DSLRs immediately sold me. I have only had camera for a little under a week and love it. The lens I initially ordered with it was a 18-200mm tamaron (100% body controlled with exception of focus), it works reasonably well and is good for general shooting. However, eager just to try a new (by new I mean old/vintage) lens, I purchased an auto Chinon 1:1.9 50mm

The lens seems to work well until I open in it all the way up (1.9) once I do this I'm stuck at this unless I use the small little metal post that is on the mount of the lens (I'm sorry for poor terminology, I tried to research this and was unable to figure anything out just because of my general lack of knowledge)

[IMG]
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(In the picture above, the pen is pointing at the "metal post")

Initially I thought the aperture ring was broken because if turned the dial to the maximum (f16) nothing would happen (on or off the camera), it would simply stayed @ 1.9. However if I took the lens off, set the aperture ring to f16(or anything not 1.9) and gave a gentle push to the "metal post" the aperture would move. Once the aperture would move I could use the aperture ring freely from f16 to 2.2 ( in between 2.8 and 1.9)

The fact that I can move the aperture at all makes me feel as if it may be a user error but I don't know. All help is appreciated. Is it a problem with the lens or simply a user eror?
Thanks


More photos:
Aperture open 100%
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[/IMG]

Aperture ring set to 16, however, aperture open 100%
[IMG]
[/IMG]
[IMG]
[/IMG]

Played with "metal post" now ring and aperture are in sync and stay in sync as long as i don't go to 1.9 (when off the camera)
[IMG]
[/IMG]
[IMG]
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Last edited by sethrw; 03-20-2012 at 05:58 AM. Reason: correct pictures
03-20-2012, 07:05 AM   #2
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Does it move easily and freely when you're playing with the aperture arm, or is it a little stiff and slow to move? If it's moving quickly and freely, it sounds like some springs might have been unhooked (either during a home repair or just over time or a jostle). If it's pretty stiff otherwise, the blades are probably oily and need a cleaning, which isn't the easiest task in the world, but it wasn't the most difficult (at least with a vivitar 2.8 135mm) either.

If it's spring related, unless the spring is actually broken, it should be relatively easy to repair if you can get your hands on a cheap set of dental picks or something along those lines. Just usncrew the mount screws and pull it off, and that may just be enough to reach in and re-hook the springs.

--------- edit ----------

I see you say it's generally working now - I'm guessing that it's also sluggish and probably the blades need to be cleaned.

Last edited by pezmaker; 03-20-2012 at 07:06 AM. Reason: updating
03-20-2012, 07:38 AM   #3
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I would describe it as slow/sluggish. and I can see some grease on the aperture when at f16 is there any relatively easy way to remove some of the grease?
03-20-2012, 07:53 AM   #4
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QuoteOriginally posted by sethrw Quote
it would simply stayed @ 1.9. However if I took the lens off, set the aperture ring to f16(or anything not 1.9) and gave a gentle push to the "metal post" the aperture would move. Once the aperture would move I could use the aperture ring freely from f16 to 2.2 ( in between 2.8 and 1.9)
I have had a lens wit a similar behaviour and it is most likeky dirt in the aperture coupling mechanism and/or a worn spring in the same mechanism. Such things can be cleaned and repaired but not by everyone and I doubt your lens is really worth it. There are many good MF lenses in this class to be found at very reasonable prices so, I would settle for a sustitute rather than facing the risk of a lot of frustration and ruined shots.

03-20-2012, 11:57 AM   #5
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I would prefer to fix if possible for a few reasons
A,I don't just want to give up on it
B, I may find other lenses in the future that have a similar problem and it would be beneficial to know how to fix them
C, it's spring break and I have time to mess around with it

Any ideas on how to clean the aperture blades?
Thanks
03-20-2012, 12:09 PM   #6
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to fix the blades, you need to remove both the frong and rear lens group, and then wash the blades with solvent, usually on a Q tip.

each lens and manucturer come apart differently especially the front group. the rear group usually will unthread as a unit.

if it is not sticking blades, it could be interference on the aperture activating lever that's the name for the small little metal post . if this lever is bent slightly sideways it will interfear with the slot in the lens mount
03-20-2012, 12:27 PM   #7
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Hi Seth,
Not a permanent fix, but the following may let you test to see if the lens is otherwise OK.
Warm the lens, eg sit it on your computer or ups box.
Set to f/22 and flick the lever 50 times or so.
It may free up enough to let you do some test shots at f/8.

I have a couple of old ones that get sluggish in the winter but
expose OK right down to f/22 in summer.
03-21-2012, 01:17 PM   #8
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How is this coming along?
I was thinking about buying the same lens off ebay, so I am interested in the outcome.

03-21-2012, 02:45 PM   #9
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Do you have a kocal shop that can clean it for you?

@Na Horuk Izgleda da ima zamaščeno zaslonko. Vprašaj prodajalca za fotko popolnoma zaprte zaslonke.
03-21-2012, 03:20 PM   #10
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Take it apart, its a good learning experience. I just took apart my Pentax A50mm 1.4 and got it cleaned relubed and back together again, biggest thing was getting the 2 halves of the gears for the focus back together, near impossible to the get the angle just right to start them, and there are like 6 or 8 possible clock positions, it doesn't work after reassembly unless its clocked right so mark what is aligned with what before its fully apart. Also I don't know about that lenses construction but mine had a ring under the front cap held by 3 screws, if you loosed those 3 screws (I removed the ring entirely) you have to reset the fine adjustment on the focus afterwards (not that hard).

You will need a set of these Amazon.com: Screwdriver, JIS Type S Set, 5Pc Plastic Handle: Home Improvement as those phillips screws aren't phillips, and possibly an adjustable lens spanner wrench, may also need a super tiny flat blade screw driver.
Also at the suggestion of others I used regular automotive white lithium grease (good in heat and cold and doesn't seperate) to relube my lens (grease VERY sparingly) seems to work perfect though its a tiny bit stiffer on the focus than some of my other lenses, the extra dampening is kinda nice.

If the blades are greasy (mine werent) its rather hard to clean with a physical tool without damaging them, seperate that part from the lenses and try blasting it with automotive brake cleaner with the aperture closed (dont use the stick on the can or get too close) then work it a bunch of times with a pick or something operating where the lever would go and spray it off again. I've never tried this myself so I don't know what will actually happen (sorry ) but brake cleaner eats grease without eating plastic or rubber and evaporates fast without a major residue (dont get it on the other lens parts though). The grease likely seeped out of the other areas when the lens heated up in the sun (or just cheap grease) you'll likely need to clean everything up and relube it.

EDIT: if its only jamming wide open I have a hunch that the problem is mechanical and something is corroded or bent, but youll likely see the issue with it apart, on mine i just needed to unscrew the back cap (watch for small parts) and I could unscrew the rear lens element housing by hand allowing access to the blades and associated parts.

Last edited by PPPPPP42; 03-21-2012 at 03:27 PM.
03-21-2012, 03:31 PM   #11
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QuoteOriginally posted by Giklab Quote
@Na Horuk Izgleda da ima zamaščeno zaslonko. Vprašaj prodajalca za fotko popolnoma zaprte zaslonke.
Ha, bo res treba. Skoda le, da sem ze nabavil nek starejsi Pentax prek spleta in se cakam, da pripotuje do mene. Je pa zanimivo, da je na tem forumu kar nekaj clanov iz nase male drzave.
03-21-2012, 10:28 PM   #12
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QuoteOriginally posted by Na Horuk Quote
Ha, bo res treba. Skoda le, da sem ze nabavil nek starejsi Pentax prek spleta in se cakam, da pripotuje do mene. Je pa zanimivo, da je na tem forumu kar nekaj clanov iz nase male drzave.
Bi znalo biti ker je pri nas Pentax najcenejša stvar sploh...
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