Minolta Rokkor 28/2 (MD-II), something on inside of rear el

Spokklocka · Joined: 14 Jan 2015 Posts: 50

Hello,

I have a Minolta 28/2, MDII, that is not the last and optically best version, but quite an interesting thing nevertheless, esp. the bokeh at mfd.

Shining a light through it something appears to gradually cover the inside of the rear element with the exception of a couple of round "holes". I shall try to take a photo of it this evening.

Have not seen a repair guide online, text document or on youtube, so was wondering if anyone has any comments on this? I do at least not need to bother the focus barrel since the lens mechanics do not have any issues.

Edit. Now with more imagery!

"Balsam separation" or fungus? Could almost believe it is a network of small cleaning scratches, except for those "holes". Looks as if on inside of rear element, can only be seen if light shone through the lens.

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

I have no idea what that it is, but I gotta tell you my gut reaction would have been to walk away no matter the price. It looks, for lack of better word, bad.

Rigel · Joined: 26 Nov 2015 Posts: 121 Location: Belgium

I do not know in how much this lens resembles the Minolta W-Rokkor-X 28mm but that one is very easy to take apart.
My guess is that the "scratches" are fungus filaments. I doubt it that real scratches would run over each other in different directions. Just my 2 cts ...

Spokklocka · Joined: 14 Jan 2015 Posts: 50

Hi, thanks for your replies.

Gut reaction if we were discussing a sale? Sure, though your typical ebay seller does not shine a light through lenses and show. Shining a light through is the quickest way to become depressed about a lens, just try it if you have several Smile

Rigel: I'm inclined to agree. Cleaning scratches on the inside of the rear element seems less likely on its own even, but I have heard of balsam separation in Rokkors and I've seen (different kinds of) fungus prior.

Easy to disassemble is great, and I've seen the yt-channel of Matt Bernier. The 28/2 might be different inside though and personally I think it's easier to attempt disassembly when there's an instruction for the precise model. That may change after a couple of operations as experience is gained I suppose.

Rigel · Joined: 26 Nov 2015 Posts: 121 Location: Belgium

I always suggest potential sellers/buyers to ask the parties involved to perform the "Ken Rockwell" flashlight test Wink

http://www.kenrockwell.com/tech/flashlight-test.htm

Then to re-evaluate the material Wink

.. and FWIW there is an excellent tutorial (among many others) on the disassembly of the Minolta W-Rokkor-X 28mm on youtube.

https://www.youtube.com/watch?v=Hp7uTqxec9c

BTW .. for AFAIK and if memory serves me right for my copy, I cannot remember any balsam glued lens set in the rear group but I've taken apart a couple of 28mm's lately so don't hold it against me if I have the wrong one in mind Wink

HTH

Spokklocka · Joined: 14 Jan 2015 Posts: 50

Rigel: Yes, that's Matt Bernier's channel, he's pretty good at showing how it's done provided you know a few basic things. Judging by the schematics of both lenses on Artaphot they don't look very similar internally though.

Do sellers usually agree to shine a light through the lens for sale and show / swear by the result, particularly ebay ones?

This MDII 28/2 behaves as expected optically, i.e sensitive to flare, pretty bad corners, sharp in the center at f/2, creative bokeh. Kind of hard to know whether fungus is alive and spreading. I keep my lenses dry and compartionalized when not in use so there shouldn't be optimal conditions for spreading. If it is fungus. This particular specimen came from a no-returns auction, seller with good rating, decent price, seller was exiting his collection or so he wrote.

Will soon take delivery of a Vivitar (Kiron) 28/2 and (if it doesn't look the same internally) compare it optically and mechanically to the Minolta.

Lloydy · Expire: 2022-01-01

I would be fairly confident in saying that the lens is fungused, but equally confident that it's still at a stage where cleaning the element would be worthwhile. I think most of the contamination could be removed, and hopefully a large amount of etching hasn't taken place.
If fungus can be removed early enough the difference can be dramatic, but once etching takes place the lens is permanently damaged.

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

Rigel · Joined: 26 Nov 2015 Posts: 121 Location: Belgium

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

Not kidding at all. About the only thing that a flashlight test does is it lights up dust and make it seem about 100 times worse than it is. In no way it is a measure of a lens quality. So I have no intention to indulge whims like that. Samples, additional pics of the lens? Sure. Flashlight test? Uh-uh.

Spokklocka · Joined: 14 Jan 2015 Posts: 50

Loyd: Thanks. If I find any guide for the 28/2 I'll try it.

Gardener: It shows everything well, including dust. Some things are almost invisible without a torch. See the Ken Rockwell link, he does say that dust is normal. Fungus, haze, cement separation, scratches. Ebay is like a lottery wheel in my experience and I think most would not do the torch test upon request but I haven't ever asked. Threatening with negative feedback and then going through a return is a hassle for both seller and buyer so perhaps more should agree to the torch test.

As for the same mechanically, I didn't mean the schematics for the sake of dissassembly, I meant weight, focus ring resistance etc. The MD 28/2 feels pretty good although not great.