Jupiter 8 - Some general questions

[mszargar]

I have noticed the following in a recently purchased copy of J8 (1966 - Chrome):

1) The lens is somehow loose. No matter what part of the lens I grab, I can slightly move it to left and right while it is firmly screwed on the lens mount. Is this normal? (my apologies for being the newbie that I am, but this is my first experience with a camera that is twice as old as me)

2) Focus ring turns past the 1, and past the M sign (does this mean macro?). Overal, the ring moves very smoothly, but once every three or four times, when I turn it to its limit past M it gets stuck and needs some pressure to turn back. Is this a kind of primitive focus lock mechanism, or is it a defect (or neither)?

3) Aperture ring moves from past 2 to 8. It is not correctly aligned. Actually the actual f number lines up with 5.6 on the DOF scale... I know that I can fix this by opening the lens, but is there any reason to do so? Can't I keep lining up with 5.6?

4) Again about the aperture ring: When I received the lens the aperture ring could turn only to 5.6. I detached the lens from the focus mechanism according to the instructions, just to see if I could possibly fix it. The two elements were very tightly screwed together, but I finally made it. After some investigation I put everything back as tight as possible, but now the aperture ring can turn past 5.6, and up to 8. Have I not tightened the elements to each other enough? Can this create focus issues?

5) This is less straightforward as a question, but how sensitive are the filter screws of a lens? My copy is very very slightly bent inside in one corner. I could not see it on the auction site, I can not see it without critical eyes, but I can see it when I look at it very closely. Probably the lens has had a very slight shock. Should I order a filter, or is it not worth it?

Many thanks in advance,
Mah

 

[wolves3012]

I have noticed the following in a recently purchased copy of J8 (1966 - Chrome):

1) The lens is somehow loose. No matter what part of the lens I grab, I can slightly move it to left and right while it is firmly screwed on the lens mount. Is this normal? (my apologies for being the newbie that I am, but this is my first experience with a camera that is twice as old as me)

There were at least four silver versions of the J-8. If it's the type that has a non-rotating front, then the answer is no it shouldn't move except for a small amount of play that's normal.

2) Focus ring turns past the 1, and past the M sign (does this mean macro?). Overal, the ring moves very smoothly, but once every three or four times, when I turn it to its limit past M it gets stuck and needs some pressure to turn back. Is this a kind of primitive focus lock mechanism, or is it a defect (or neither)?

The "M" is for metres (some lenses are in feet, so it tells you which) and it's normal to go a little past the 1m mark. If you keep going, the threads are at the end of their limit and can tighten up, I'd say that's normal. Just don't go quite that far.

3) Aperture ring moves from past 2 to 8. It is not correctly aligned. Actually the actual f number lines up with 5.6 on the DOF scale... I know that I can fix this by opening the lens, but is there any reason to do so? Can't I keep lining up with 5.6?

It should go from f/2 to f/22, although it's normal for one end or the other not to match up exactly. If it doesn't go through this range, either the scale is misaligned, you're not reading it correctly or (if the full range isn't available) the aperture mechanism has been incorrectly re-assembled. Assuming you have the full range, there are 3 tiny screws set at 120 degrees around the aperture ring. Loosen them very slightly with a jeweller's screwdriver, move the ring to the correct position and re-tighten the screws - do NOT over-tighten, they don't need much.

4) Again about the aperture ring: When I received the lens the aperture ring could turn only to 5.6. I detached the lens from the focus mechanism according to the instructions, just to see if I could possibly fix it. The two elements were very tightly screwed together, but I finally made it. After some investigation I put everything back as tight as possible, but now the aperture ring can turn past 5.6, and up to 8. Have I not tightened the elements to each other enough? Can this create focus issues?

As above, it should move the full range from f/2 to f/22. See below for a helpful link.

5) This is less straightforward as a question, but how sensitive are the filter screws of a lens? My copy is very very slightly bent inside in one corner. I could not see it on the auction site, I can not see it without critical eyes, but I can see it when I look at it very closely. Probably the lens has had a very slight shock. Should I order a filter, or is it not worth it?

Many thanks in advance,
Mah

Any deformation of the filter ring means it will very likely not accept a filter. To be honest, the only way to see (if the damage is slight) is to try one. If the dent is obvious, forget it.

If you're happy tinkering with it, I'd say a full stripdown, clean and re-lube will make your lens much more enjoyable. For an excellent article on the lens, download the PDF file from this page (yellow links on the left):
http://pentax-manuals.com/repairs.htm

 

[mszargar]

Thank you for all the time you have put in answering these questions...

There were at least four silver versions of the J-8. If it's the type that has a non-rotating front, then the answer is no it shouldn't move except for a small amount of play that's normal.

Exactly, I have this small amount of play that I am not used to... So, it is OK.

Just don't go quite that far.

Noted.

Assuming you have the full range, there are 3 tiny screws set at 120 degrees around the aperture ring. Loosen them very slightly with a jeweller's screwdriver, move the ring to the correct position and re-tighten the screws - do NOT over-tighten, they don't need much.

I will try to find the screw driver to do it. Seems to be pretty straightforward.

Any deformation of the filter ring means it will very likely not accept a filter. To be honest, the only way to see (if the damage is slight) is to try one.

I haven't been able to find a filter this size yet, but seems that the filter story is compromised. I can still return the lens to get another copy, but this is the original lens that came with this body and it is also pretty sharp. I am not willing to incur the cost of sending this copy that I like back to Ukraine with the risk of receiving a copy that is not as well-kept.

If you're happy tinkering with it, I'd say a full stripdown, clean and re-lube will make your lens much more enjoyable.

I am pretty sure somebody has CLAd this lens not a long time ago. It is extremely clean and smooth. I think the same person has failed to align the aperture ring correctly.

For an excellent article on the lens, download the PDF file from this page (yellow links on the left):
http://pentax-manuals.com/repairs.htm

This website is a valuable resource. Bookmarked!

Mah

 

[mszargar]

there are 3 tiny screws set at 120 degrees around the aperture ring

Well, just to let you know that I did this and it worked... Had some hard time putting the screws back, though... Even the 1mm jeweler screwdriver seemed to be too big for them.

 

[wolves3012]

Glad to have solved it. The trick with the screws is that you don't take them out, just slacken them enough to let the ring move. They are a royal pain to get back in if you take them out - as you found out.

 

[mszargar]

The ring wouldn't go past its limits until I took all the three screws out!

The magnetic screwdriver and the loupe and the mini-tongs that came with the screwdriver set helped putting them back...

But hey, it was fun... 😉

Btw, I think I will try this soon for the small bump on the filter ring: http://feuerbacher.net/photo/repair/FilterRings/FilterRings.html

If done correctly, the aluminium body should not resist much against the pressure. After all, the deformation is very small, although large enough to prevent the filter. Then, I will get to keep the body and its original lens together.