Help needed to disassemble a Soligor 250 f4.5

mgvh · Joined: 27 Feb 2014 Posts: 4

I came across a Soligor 250 f4.5 for rather cheap, and it even had a T4 to Pentax M42 adapter on it. Based on the positive report of luisalegria (http://forum.mflenses.com/soligor-tokina-250-4-5-t4-the-rarest-t4-t11795,highlight,+soligor%20+and%20+250.html), I took a chance.
Turns out it also had a nice chunk of fungus on one of the inner elements.

According to an old diagram I found, this lens only has 4 elements in 4 groups.
I'm wondering if anyone know hows to take this thing apart to try to remove the fungus. Here's what I see:

Those two screws on zoom part of the barrel are the only screws I see other than those 3 little ones near the mount. Do I just start unscrewing the screws and carefully document to see what I find? I've looked online, and it appears that some lenses disassemble by using a calipers and unscrewing a plate from the front lens, but it doesn't look like that can be done here.
And should I start pulling out screws, any idea what to expect?
For a cheap and old lens, I'll agree w/ luisalegria that it takes quite nice pictures, and the fungus spot is not really noticeable in most shots for now. (It does a better job at 250mm than my DAL 55-300 at 250mm.) Is is better to just leave it be until the fungus becomes a problem? (In the meantime, I'll give it sun exposure to at least try to halt the fungus growth.)
Any help would be appreciated! Mark

mgvh · Joined: 27 Feb 2014 Posts: 4

I'm guessing the pics aren't showing because I'm a new user. I have been lurking for quite a while as I have begun to brave the world of manual focus and old glass.
UPDATE: Now the pics appear!

visualopsins · Expire: 2025-04-11

Welcome Mark!

luisalegria · Expire: 2018-01-18

I have never disassembled mine, so I can't help much. I have disassembled plenty of other lenses, so there are some general principles.
Generally this is a very simple lens, so you should be able to tell whether the fungus is near the front or rear elements.

If near the front, my usual procedure would be to unscrew the name ring, which generally permits removal of the front cell, or at least the front element. Fungus particularly likes to be behind the front element, or behind the rear element, or on one of the surfaces by the aperture blades. In this case the name ring would have to be removed with a friction tool. Thats anything sticky or rubbery that can give you a good circular grip. This lens has no slots on the name ring, which makes this necessary.
In some cases I have had to drill holes in the name ring to give points fro my lens spanner to grip.

If the rear, you would have to remove the T4 mount. There are a lot of screws in this area that give promise of permitting dissassembly of this section. Behind the mount, usually, there is a tube holding the part of the optics on the back side of the aperture.

BTW, I note plenty of screws around the tripod mount collar on mine. They are small grub screws.

I wouldn't remove the focus grip unless totally stuck. Its not usually necessary for what you need to do in this case. Its possible that removing it will reveal screws that permit you to remove the front cells, but generally this isn't the case.

I wouldn't unscrew things willy-nilly. Best to go with a plan of attack and leave things as they are unless you really need to work on them.

Also consider just leaving the fungus alone. That in itself shouldn't affect results noticeably. I would be more concerned if there is a fog or haze.

visualopsins · Expire: 2025-04-11

Iirc, extend the lens by focus closest, then unscrew front section from lens body -- Takumar 200/4 uses same method -- the front element(s) remain in the unscrewed front section...

luisalegria · Expire: 2018-01-18

Doesn't look like that would work on mine. It does not yield to twisting.
It may have a setscrew hidden under part of the focus grip preventing unscrewing of the front barrel. Lots of lenses have that. Sometimes the setscrews are accessible, sometimes not.

mgvh · Joined: 27 Feb 2014 Posts: 4

Update on this lens...
I was able to take off the front name plate ring, but the front lens element still did not come out.
I'm rather sure, however, that the fungus is on the inside of the second element, so I didn't probe further there.
I did more testing, and it is a lens that can produce very good results. Using a Pentax K-30 which has in-body shake reduction, it works well handheld. It's easy to focus whether using the viewfinder or liveview. It is easier to focus at 4.5 and then close down. With this T4>M42 on the Pentax this works great, because I can use Av mode and the camera will automatically adjust shutter speed.

As for the fungus, I am hesitant to start dismantling randomly a lens that works well in other respects. I really can't notice any effect of the fungus from f4.5-f11. At f16 it's slightly evident if you're looking for it. At f22, it is noticeable as a very small dark or light spot depending on the lighting and background. Since diffraction starts kicking in at f16, I'm not likely ever to go higher than f11, and even if I did, the spot is fairly easy to fix in post processing.

So I've decided to just let the fungus be. I.e., I'm taking luisalegria's advice!

It's in a dry place now, and I left it in the sun for a couple days, so the fungus does not appear to be growing anymore.

Thanks for your help!