Spiratone preset 105mm f/2.5 construction?

55 · Expire: 2022-06-15

All,

This isn't a query about the optical layout of Spiratone's 105mm f/2.5. Rather, I'm wondering if my copy is missing a washer or spacer where the front end screws into the aperture ring / barrel?

When the upper part of my preset lens is screwed in securely, the aperture ring is very difficult to rotate.
And to get the aperture ring to rotate freely, I have to unscrew the upper part enough that it's not secure.

Can anyone tell me if my Spiratone is missing a piece?

Here's a photo of my lens:

#1

visualopsins · Expire: 2025-04-11

Guessing...

1. That flathead screw in the silver ring is some sort of adjustment. Of course you've already tried that... Smile

2. Have you seen the effects of loosening the front group? If sharpness is best with "unscrew the upper part enough that it's not secure" I'd say a washer is missing...

EDIT: someplace around here is a post describing visual effects of changing the distance between front & rear groups...

55 · Expire: 2022-06-15

RokkorDoctor · Joined: 27 Nov 2021 Posts: 1272 Location: Kent, UK

I would hazard a guess that nothing is missing:

a) it would be unusual for a lens of this construction to have the front cell vs. back cell spacing adjustable by shims; usually this is a pre-machined accurate dimension of the barrrel those cells screw in to.
b) It would be odd to have both the looseness of the aperture ring as well as the front cell vs. back cell spacing adjusted by the same shim, as then you couldn't adjust both optimally at the same time.

Many preset lenses of this era have a type of construction with three main components, and collimation shim(s):

1) the mount
2) the helicoid assembly
3) the optical assembly (main barrel with rear cell, front cell, aperture assembly and aperture controls).
4) collimation shim(s) between the helicoid assembly and optical assembly

Later lenses (post preset-era) usually forgo the collimation shims but have a facility to adjust collimation on the helicoid assembly itself.

I would suggest that the adjustment of the aperture ring looseness is actually done from the rear of the optical assembly, possibly by a screwed-on retainer ring held in place with thread-lock or a setscrew.

It is also entirely possible that someone reassembled this lens before and has incorrectly positioned a few shims required for adjusting the looseness of the aperture controls.

The optical assembly can often be removed for access of the cells and aperture controls by removing a circular nut that holds it fixed to the helicoid assembly; this nut often needs to be accessed from the rear and is sometimes deeply recessed requiring removal of the mount first.

CAVEAT: I have no experience of SPIRATONE lenses of that era, so their construction may well be different...

55 · Expire: 2022-06-15

BrianSVP · Joined: 09 Jun 2023 Posts: 301 Location: Philadelphia

I haven't had/worked on one of these in a while, so my memory's a little hazy on this one, but just spitballing here - on some preset lenses, the aperture preset ring is detented and spring loaded so it is not easily turned unless the ring is pulled back or pushed forward in order to prevent it from turning when using the open/close ring. Perhaps this is the case here?

BrianSVP · Joined: 09 Jun 2023 Posts: 301 Location: Philadelphia

A little nitpick - the shims used in these lenses are not correctly described as "collimation" shims. Collimation refers to adjustments in the axial and tilt alignments of the lens elements, whereas the shims being referred to here are merely intended to adjust front-back focus of elements/groups/cells. They are more correctly referred to as "focus shims" or "focus spacers."

This is the same reason I often get a chuckle at people that claim to have "collimated" various prime lenses, as they quite literally designed in a way with fixed mounts so that they cannot be collimated at all! Really, the only camera lenses that can be collimated at all are certain high end zooms that use adjustable eccentric screws in their focus/zoom mechanisms in order to ensure various groups remain collimated throughout their full range of travel.

55 · Expire: 2022-06-15

RokkorDoctor · Joined: 27 Nov 2021 Posts: 1272 Location: Kent, UK

Lloydy · Expire: 2022-01-01

Your Spiratone is the same as my Sankor Series E.

I've just taken the front off my lens and there is no shim or any other part between the two parts in your picture.

The aperture ring is a friction fit between the two parts and is lubricated lightly with grease. Mine is 'firm' as it rotates, and it does have a sprung ball to click the apertures. The preset ring is a lot looser and does have slight play between the chrome trim ring and the focus ring.

With the front part seperated from the lens body the aperture ring turns with the same firmness as it does when screwed back in firmly.

Maybe the grease that lubricates the aperture ring is dried out and sticky? or if the ring does not 'click' then maybe the ball has come out of its location and is stuck somewhere between the two parts?

55 · Expire: 2022-06-15

55 · Expire: 2022-06-15

After two weeks, I finally found my missing 105. It turns out it was exactly where it was supposed to be!
I recently "organized" some of my lenses to make them easier to find. Except I forgot about my new system, so I was looking where I thought the 105 should be, instead of where it was... Mr. Green

Anyway, I've checked out my lens again and it's just as Lloydy described the Sankor Series E version. Everything on my copy seems to be where it belongs.

So I cleaned off the parts and added some fresh grease. With the lens reassembled, the upper aperture ring (with numbers) is still stiffer than I'd prefer, but it works.

I'm satisfied because I now know my lens isn't missing any pieces. And since I shoot this lens wide open 90% of the time, the stiff aperture won't be a big problem.

Thanks again for all the replies.

Friends