Sigma MINI-WIDE 28mm question

[wrep]

Hello!

I have just discovered this wonderful world of manual lenses..

My first buy was a CHINON 50mm 1,7 and I really like it!

My secon buy was a SIGMA MINI WIDE 1:2,8 f=28mm MULTI-COATED.
When I recieved it and started to inspect the lenses I discovered that one of the lenses inside has a very coarse/grainy surface it looks like one million small small scratches if you look into it from the back.

Now my question: Should it look like this? Is it some kind of anti-reflex surface or is the lens broken?

Regards // Per W

[wrep]

I tried to photograph it but it was kind of hard... but anyway this is how it looks. (click the images for full size)

[wrep]

I found this topic:

http://forum.mflenses.com/thrift-store-sigma-28-2-8-mini-wide-macro-lens-t6422,highlight,sigma+28mm.html

[tango]

Possibly you can clean the internal surface of the last rear lens. It seems to me that there it is the problem.

[wrep]

I think it´s one of the lenses in the middle the one that is very curved

[luisalegria]

I'm sorry to hear about your problem. It looks just like what my lens has. One of these days I am going to try to fix it, but I don't have much hope.

I am sure I can disassemble the optics and almost sure I can clean the haze with acetone (the haze is probably from the oil or grease). But I am not confident that I can put it back together.

This is a complex wide angle and the assembly tolerances are very critical. I'm not sure that an amateur like me can reassemble this accurately and still have a decent lens. I disassemble and clean glass all the time for tele lenses, and have had good success, but tolerances for those are not so tight.

[CarbonR]

I received a Sigma Mini Wide 28/2.8 in M42 mount wednesday (with Spotmatic SP, Staks 50/1.4 & 200/4 for 102 EUR), the lens looks like new, but has points one a inner element too. There seem to be aroud the diaphragm, but I tested it wide opened both at infinty and at it's closest distance of focusing, it seems to have no problem, this is rather good for a wide angle wide opened. I had the II version in PKA mount, the results were equivalents, but the inner elements were clear

[wrep]

[luisalegria]

If you can return it I suggest you do that, unless you want the adventure in lens repair. That can be fun and very satisfying when you succeed.

This is not a rare or expensive lens and it shouldn't be too hard to find a good one. If this was a Zeiss Flektogon you picked up as a bargain you should of course try the repair, as you would have much to gain. But not in this case.

The equipment I am thinking of are, beyond the usual and unusual hand tools, a collimator appropriate to this lens. And besides that the knowledge and skill to use them to get the spacing and alignment of the lenses right. Usually I just happily push lenses back in to their sockets and screw in the retaining rings without a care, but I don't think that will work well in this case.

[CarbonR]

Did you test it, before thinking of throwing it away ?
Mine has points like yours, but is rather sharp wide opened so I don't worry about it

[wrep]

Hello again!

Yes I have tried it... the pictures gets like a white milky fog look.. and it can´t handle direct light at all... could maybe be used for some artistic-effect photo

The seller said he would send my money back, but I still haven´t got them.. I´ll give him some more days before he gets a negative feedback..

If he doesn´t pay I´ll use it as a lesson in lens-mechanics maybe I can bulid some kind of adapter from it..

// Per

[JoeCool]

i had one lens, a Yashica ML which had similar little spots on an inner glass surface, when it arrived. Optically it seemed without impact, and after some time it disappeared. Perhaps it was some condensed moisture inside the lens. You could try to put it in the sunshine on the window shelf.