Sigma Mini-Wide 28/2.8 M42 - Repaired !

[luisalegria]

I bought this lens almost exactly 30 years ago. When I pulled it out of the old camera bag two years ago, I found that an inner element had developed a bad haze, and it was unusable. I though that was the end of it, but last week I resolved to open it and see what could be done.





Internally it is a lightly-built thing, rather cheaply made of thin aluminum. Certainly this thing is no Takumar. However, it was quite easy to disassemble from the front, except that I had to drill holes in the name ring for a lens spanner. Once the name ring was off everything in front of the aperture just fell out.

The inner, highly curved second element had the haze, which proved difficult to clean. I used alcohol, acetone and lighter fluid, and I eventually got almost all of it off, save for a bit that may actually be damaged coating.

One warning if you want to try this on another Mini-Wide - the third element, just in front of the aperture, is very small and is convex on both sides, so its not easy to tell how it goes.

Anyway, now it is fully functional, but not so nice looking as besides the holes, it has lost some paint on the side of the second element.

The Sigma Mini-Wide was a quite popular product back in the late 1970's-early 1980's. It was cheap, it worked well, and it focused very close, which was Sigma's claim to uniqueness in those days. Its still quite good as a close-focusing wide angle even now I think, and I have seen several excellent pictures in this forum taken with them.

The M42 version I have has a stop-down button, not an A/M switch, which I thought was a disadvantage. However, this feature is growing on me, it is even better than a good preset mechanism, focus wide-open and press to stop down just before shooting. The only remaining problem is that pressing the button adds tension to my grip and risks shaking the camera.

Performance is quite good by my standards. Its almost, but not quite as sharp in the center as the S-M-C Takumar 28/3.5 at usual shooting apertures - well thats my subjective opinion anyway. Little to no risk of flare - in spite of the haze and cleaning. It does indeed focus very close, and there is a possibility of getting a nice "3D" effect. There is some barrel distortion that would probably get worse in a full frame camera.

[Nesster]

Super presentation, as always, and the pics look really good.

Re. haze and lens cleaning (I hear this works on fungus too): Ponds cold cream. Let the lens sit in some for a while... supposedly an old camera repair trick. I haven't had the opportunity yet to try this, as the cloudy bits cleaned up without it... which was a good thing, except I really wanted to try out the Ponds

[Jesito]

Great job, Luis!

The miniwide is not commonly very apprecitated, but I like it. It's a very capable lens, and renders nice colours.

Regards,

Jes.

[themoleman342]

The pond's 'trick' works like a charm. Buy a big jar from store and you'll have it for life. I've cleaned probably 15 or so lenses now and the fungus wipes right off without any coating damage. Have a good secondary optical cleaner though as the Pond's gets wickedly greasy.

Nice pictures. I like the dog the best for colors. Did you up the saturation any? Or was this natural?

[luisalegria]

Thank you Nesster !

Very cool. What year was this ad from ?

Unfortunately, though I bought this thing new in 1979, with case, caps and papers, it did not come with the allegedly superior hood. Maybe that was a US promotion. I got mine in Manila.

[luisalegria]

The dog needed a bit of extra contrast, but I didn't change the colors.

I usually have a "medium" setting for saturation on the Pentax K100D.

[Nesster]

That ad's from '78

[kestersonn]

I too got a Sigma 28mm just like yours with a milky inner element. You didn't have to go the route of drilling the front nameplate. For those about to take this lens on, just approach it from the back. First, extend the focus out as far as it will go. Take out the small set screw on the lens barrel (there's only one). Take out the screws holding the lens mount on the back. There are only three that hold it, but there are several screws there. If you loosen all of them and carefully lift off the back assembly, parts should not go flying. After this is off, remove the aperture adjustment ring, taking note of its position and the ball bearing on top. It has a long flange that guides the aperture blades. Looking down in the lens barrel, you'll see three screws in the back of the name plate ring. Back these out. Carefully lift out the lens tube assembly. Do this slowly and precisely, as the lens elements are loosely held in place by friction. Once out, carefully place the lens assembly on tissue paper. Be careful at this point, all of the lenses will fall out and it will take many hours to figure out which direction they go back in! I laid the lens assembly on its side and began slowly removing each lens. My lens only required some light cleaning with Windex and lighter fluid, I was lucky.
For reassembly, I found it easier to put the lenses back in their tube in reverse, by putting the tube on its back, and using tweezers, putting the lenses back in facing up. I then put the lens barrel over the tube, held the front, and reversed direction so the lens barrel and lenses were now facing down (on tissue paper of course). Now, put your three screws back in and reassemble the lens. Be careful not to lose the ball bearing on the aperture ring.
Also, be careful of grease inside the barrel housing and aperture ring. Keep a towel nearby to wipe your hands before touching any lens, the lens tube, or the outside of your lens barrel.
Hope this helps.

[mo]

Could someone post a shot of what this ponds cream looks like?just checking it is what I think it is

[Bruce]

http://www.amazon.com/gp/product/B001ECQ4RG
PONDS /\

[mo]

..good that was what I was thinking.any reason why this works so well?

[Farside]

[mo]

I am wondering who discovered it works and how?? Did someone actually just drop their lens into it and wiped it off thinking hey this works well for removing fungus....OR is it a lens cleaning product that was found to benefit skin?

[fates]

The way the story goes, there was a 1960's fashion fotog that bedded a lot of model birds in his time. He was a regular Michael Caine, but never let a good time end well.

Once he got into a scuffle with a jilted lover who flung his lens bag into her changing mirror. As the shards of glass danced across the floor, one dirty, fungus ridden Biotar flew out from the bag and fell into her new jar of cold cream.

"You got your cold cream on my lens!?," he shouted.

"You got your lens in my cold cream!," she retorted.

But the real winner was a junior copy writer, who stood dumbfounded in the corner from the Martin agency, which had just got the Reese's Peanut Butter Cups account earlier that week.

[kanirasta]

I've recently got one with some haze on it. Since it was so cheap, I decided to give it a try and clean it.

I was able to disassemble and re-assemble it clean, but I wasn't very satisfied with the results so I decided to try again.

Sadly this time I must have swapped some element around because I can't make it focus properly

Do you have a diagram of the lens or know which design is similar so I can try to locate the element that's placed wrong?

Thanks in advance!

[luisalegria]

Dumb me - I had my notes right in this article.

There are three elements in front of the diaphragm - all three are convex towards the front. The third element in front of the diaphragm is easy to put in backwards. I suggest you disassemble again and try that.

I did not disassemble anything behind the diaphragm.

[francotirador]

Hi Luis.
It works in reference to the CA? I have a Super Wide II and is a weak point.
Greetings

[luisalegria]

Hola !

No, I have not noticed any CA problem.

But I never notice these problems unless they are very bad.

[kanirasta]

Thank you Luis, will try that!

Gracias

[eduardo.berth@gmail.com]

I really need your help. I have just purchased this lens a days ago, 28mm mini wide, but had to open it in order to clean it but had the elements mixed when reassembling it. Can anyone help me letting me know the position of the back elements and separators? Thanks a lot!

[patrikoh]

[Sciolist]

[patrikoh]

If reassembled in the wrong way, does it show clearly in the photos?

[luisalegria]

"Great information, how about the order of the elemens behind the aperture?"

I never disassembled them, so I can't say.

[Focusthrow]