Help open a Sigma Mini-Wide 28mm 1:2.8

redivivus · Joined: 24 Feb 2019 Posts: 6

Dear Cognoscenti:

How do I open a Sigma Mini-Wide 28mm 1:2.8 from above ? I am stuck at removing the badge ring. I do have a proper rubber wrench but the badge doesn't move at all ... I see a 2009 thread where the poster drove two holes into the top lens retainer ring to use a spanner, but I didn't even get there Sad

Many thanks, -- Red

eddieitman · Joined: 12 Apr 2011 Posts: 1246 Location: United Kingdom

Front ring does not come off, take rubber ring off, there is a few holes that line up with a grin screw remove the screw and then barrel and ring come off at the same time

marcusBMG · Joined: 07 Dec 2012 Posts: 1318 Location: Conwy N Wales

Well pretty much you have to persevere. You can try a wee drop of acetone just in case there's a bit of thread locker or something, also leaving the lens on a radiator to warm it and get a bit of expansion of the metal. I use the end of a small plastic bottle thats just about the right diameter with double sided sticky tape on. I also use a short section of plastic pipe, end slightly shaped, also with tape on for this purpose - removing nameplates. Drilling two small holes in the nameplate to use a lens spanner is last resort.

D1N0 · Joined: 07 Aug 2012 Posts: 2536

I once used medical tape for that to create more friction. It worked. This was a Sigma non-vignetting but it has the same body as a mini-wide

Getting a grip by The lens profile, on Flickr

visualopsins · Expire: 2025-04-11

Then place ring removal tool on sturdy surface, press lens down onto tool, turn lens...

redivivus · Joined: 24 Feb 2019 Posts: 6

SalPro · Joined: 11 Feb 2021 Posts: 12

I hope you did not cripple your lens yet with all those advises.

MiniWide beauty ring is different than most: It is integral part of outer barrel. Removal actually very easy, no need to sweat. You extend focus to max macro, this will expose tiny screw on the bottom of the glass barrel. Remove the tiny screw and then unscrew whole outer barrel, with beauty ring on it.

I love this lens. After reading number of great reviews I decided to get one, without realizing that there are x3 versions:
Ia: narrow font beauty ring
Ib: wide font
II: it say II in wide font.

Ia appeared inferior.
Ib is superior and all optical assembly parts are metal, though some plastic outside.
II has best reviews, it appeared to me identical to Ib, but has a lot of plastic in the optical assembly and the worst part - it is glued and to me impossible to disassemble.

So, when I realized how great this Ib lens is - I went on eBay spree and for next half year I think I've caused price for these lenses to rise. I got close to a dozen of MiniWides of various vintage and mounts.

100% of MiniWides I got had significant haze.

On the only Ia I got it dried out and pitted the glass, meaning it is not cleanable. Besides the haze I've also recognized CA problems and other stuff, so, I've decided to not pursue Ia.

II , need cleaning but I've realized that cemented plastic parts is not my bargain. Tried couple and give up.

Ib are the best, optically excellent, mostly metal.
The haze is exclusively on inner surface of 3rd element. It is greasy. Front of the forth element in the same cavity is perfectly clear. Made me think that it is some king of distillation effect of specific king of petroleum jelly. I guess hands are the heater, the third gap is the chamber and the glass is the condenser.

The good thing is that all but one cleaned well and performing spectacularly!

It is my always on always ready my favorite all purpose lens.
I've separately purchased matching "perfect hood" for it, no regrets, now set is complete.

Used on A7M2.

lumens pixel · Expire: 2021-06-25

Thanks for all the information.

I am unable to distinguish 1a from 1b when looking at pics on the net. If you could post pics of each I would be grateful.

SalPro · Joined: 11 Feb 2021 Posts: 12

I'm pretty certain you got Ib, the good one.
Ia got very fine tire thread, and II thread is slanted. Your thread large and straight, meaning Ib. Show us your beauty ring?

Have you succeeded taking it apart?

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marcusBMG · Joined: 07 Dec 2012 Posts: 1318 Location: Conwy N Wales

OK this thread has stung me into action. This is how I do it redivivus.
I am not sure where my miniwide II fits in to your categorisation SalPro, it has a metal barrel, and a plastic aperture ring (s/n 1082252). it has fungus around the edge of the back of the first element, and a touch of haze on the 2nd. Pic 1, with my pipe remover.
- I use my bit of pipe with double sided sticky tape on to remove the nameplate. It was a bit of a battle but got there in the end - pic 2.
- Underneath are 3 JIS screws holding on the front barrel, I used a drop of acetone on each screw to soften thread locker and removed this to better access the front end. I marked one hole with a scratch to aid replacing in the same orientation. Now the trick is to remove the inner black metal ring holding the front elements, arrowed in pic 2. This sent me scurrying to my bits 'n bobs boxes to find something the right size. Not exact - pic 3 - but proved to be good enough.
- The front elements will now come out, I only needed to remove the first element. the slight haze on #2 pretty much came off with a lens pen. I use a dash of meths + a drop of household mould and mildew remover to moisten a dried out optical wipe tissue to clean off fungus. IME something with a detergent action is what works.

Reassembly is a straight reversal. I used a new drop of thread locker (just by scraping a wee bit onto the end of a screwdriver and then touching the screw head) on the screws.
I can add that the 24mm superwide II is essentially the same, looking at some pics I took when adjusting the infinity focus on one.

#1

#2

#3

SalPro · Joined: 11 Feb 2021 Posts: 12

Markus,

"Stung" here is not upset or offended but rather engaged, right? Then it is good!

Interesting, you got II with straight tread on the focus ring. I've never seeing that. I see it say II but looks like Ib. I do not know where it fits either. Your serial is 1.022.8xx, the one Ib i have as my primary is 445.5xx, which is much earlier.
Just checked eBay and sure enough there are a few IIs with straight and not slanted rubber. And all serials start with 1.xxx.xxx. Slanted rubber is 5.xxx.xxx?
Maybe yours is IIa and slanted focus ring is IIb?

One correction to my previous statement: It might have being back of the second element, not the third as I've previously stated, that has haze. It being a few years since I got this bug. Still, I would insist that only one surface of whole lens prone to haze.
None of my Mini-Wides had fungus, and I've seeing FUNGUS in lenses.

Now, back to construction: all copies of II I had my hand on had slanted tread and all had rear element glued, impossible to take out. I always do full cleaning and not removing rear element is not an option.

Markus, I've not encountered your version of Mini-Wide. It looks more like Ib to me. I cannot say for sure what is special about your particular copy.

Back to copies I have: I've found that taking small screws from the from of the barrel is much easier way to get to the guts. It might be possible to get there other way, but in my case it was easier to remove that tiny screw and then effortlessly take apart the rest, without any risk of damaging cosmetic parts.

For the rest of the lenses with typical, threaded beauty ring, there is a nice tool to have, amazon item B0013HFYKK or similar.
Alternatively for really stubborn pieces it is safer to use hot glue, it holds better, no danger of slippage and easy to remove without any residue.

But, per my experience with Mini-Wides I had and have, this little screw is the way to go.

marcusBMG · Joined: 07 Dec 2012 Posts: 1318 Location: Conwy N Wales

"stung" in this instance means prompted.
I have had and sold several examples of the miniwide II. I have only had one example of the miniwide (i), I took some comparison pics against a miniwide II, it was ok but not as good imo, also its colour rendering was not as true (warmer). Plus it wasn't PKA. So I haven't bothered with any since.
The one I have now doesn't have that screw you talk about, in fact I don't recall having one with that, but since I have only tried to open up a couple of these I may simply not have noticed. When you refer to straight or slanted tread you mean the rubber grip on the focus of course. I have dug out this pic of a lens I sold a couple of years ago. Both the aperture ring and the ring with the white marker button (and the focus ring?) are plastic. Slanted tread, as you say...

And I have pics of three more 1xxxxx serial ones that I sold, same as the one I have now.
I have updated the miniwide II description on pentax forums.

Your suggestion of hot glue is a good one, should have thought of that myself I do exactly the same for other diy, like holding a small drill hole pattern in place on a casing. I have thought about getting those rubber rings but haven't felt the need to splash that much for only occasional use.

lumens pixel · Expire: 2021-06-25

Thank you gentlemen.

marcusBMG · Joined: 07 Dec 2012 Posts: 1318 Location: Conwy N Wales

How about this one then SalPro :

S/N 1013744, PKA mount. Actually apart from the nameplate it is identical AFAICT to the miniwide II discussed above.
I took test pics using both of Conwy Castle today. I am still seeking the holy grail of a 28mm that, when I inspect the pics, makes me cry Da Daaa!! Neither of these make the grade. They're both sharp in the centre straight off, but the Miniwide II is soft on the right, the H.L. on the left, across the frame (apsc - K3-ii) sharpness becomes good when stopped down to f8, f11.

D1N0 · Joined: 07 Aug 2012 Posts: 2536

marcusBMG · Joined: 07 Dec 2012 Posts: 1318 Location: Conwy N Wales

very interesting info - thanks for the link D1N0. Looks like I have a wee plum.

marcusBMG · Joined: 07 Dec 2012 Posts: 1318 Location: Conwy N Wales

This looks like one of your type 1a's SalPro. Construction wise I have to say its probably the best of the sigma 28's.

Like you say, they tend to have haze on the 3rd element. Can you tell me how to remove the 2nd?

Update: no problem I figured it out. The ring holding the cemented 2nd/3rd elements unscrewed with just my fingernails gripping it. The haze was then on the concave interior surface, came off with acetone.
Will post pics against MWii next.

SalPro · Joined: 11 Feb 2021 Posts: 12

Well, folks,
I guess there is even more varieties of MiniWide outthere.

First, as per multiple requests, I took front off my favorite one. I call it Ib. You can see that beauty ring and bezel are single integral part. I also recall, actually stumble once again, to align macro scale with focus scale - bezel not screwed all way in, it backed off a bit, there is a characteristic gap between beauty ring and the nut for front element (see last image in this post). Once this little stop screw removed - there is essentially no resistance from bezel to unscrew it.

Yeah, I know, it is time to clean it. But this is my default lens on the camera and I really love it, and the results, of course.

Since my previous post I have acquired one more: This is II with straight grip and full metal construction. It was cheap and it happened to be absolutely pristine, like new in the box with no dust at all or an signs of use, original case and all accessories. Not even a hint of haze, unlike all others. I can't resist though I do not expect much from II.

As I've mentioned already, all IIs I've seeing before had slanted grip and plastic lens barrel, with rear element being essentially cemented by gluing all those plastic nuts, making that lens unserviceable. To my surprise this II has straight grip and all metal construction. this makes it IIa, and slanted plastic then will be IIb.
In the left is Ib, on the right is IIa.

It is obvious from pictures that optically they are different. Ib front is much more convex, than IIa. Performance is also very different. My Ib is still my favorite. Comparing to Ib, IIa has:
-much more distortion, like x3 more. There is not much overall distortions but comparing one to another this is obvious.
-it is a tad sharper in the center but falls apart to periphery fast. For whole frame Ib is still sharper.
-CA: whole collection of spherical and lateral. Not that much you can do in post. My Ib has essentially none, maybe tiny bit of lateral is easily correctable in post.
- IIa beauty ring is not integrated with bezel as Ib, but more traditional, you need a grip to unscrew it.

So, it looks like Ia is still the best MiniWide from all generations.

I have another one to hunt for: I've seeing listing for MiniWide in Alpha mount with auto-focus! I did not win the auction, but there got to be more. Anybody seeing these auto-focus MiniWides?

SalPro · Joined: 11 Feb 2021 Posts: 12