What are these dots inside the lens?

kido · Joined: 06 Jun 2013 Posts: 105 Location: Chile

I bought a $20 Sears 200m f/3.5 (Mamiya-Sekor, possibly Tokina made as discussed in this thread) and it arrived last week. Looks and works fine but under closer inspection I've noticed this inside the barrel:

To me it looks as if someone removed one of the elements using a chisel and scraped the paint in the process. But maybe it's something else, like a vicious paint-eating bacteria, so I figured: I'll better ask.

Whatever it is, can it affect the lens performance in any way?

Haven't really got a chance to test it properly. Here are a few snapshots, all done handheld, indoors, f/3.5, flash bounced off ceiling, shot from ~3m:

danfromm · Joined: 04 Sep 2011 Posts: 585

Its hard to be sure, but it might be Schneideritis. Vicious poorly-adhering paint on the elements' edges.

Pontus · Expire: 2016-08-25

I wouldn't worry too much about it. It doesn't look like fungus and it obviously doesn't affect the image quality, which is great.

kds315* · Expire: 2021-03-09

I agree with Dan, must likely Schneideritis

Lloydy · Expire: 2022-01-01

Possibly the result of slight condensation at some time, I've got lenses with similar marks on the internal coating / paint and can't see any problems with the images. The 'marks' on the glass are reflections.

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

Doesn't look like Schneideritis to me, looks like the black paint coming off the elements which is used to increase contrast. Sometimes the paint doesn't adhere all that well, I had one lens where it pealed off very easily, a fresh coat of black paint and it was as good as new.
Schneideritis seems to be a condensate from paint, glue, etc... that gets deposited on the element surface, the Rokkor M 28 is typically effected, and can be caused to happen if the lens gets very warm, its elements are glued in and no way to clean elements... Very stupid IMO.

pd1987 · Joined: 08 Dec 2013 Posts: 74 Location: Poland

If the lens was disassembled that might be some mechanical damage or coating layer scratch. It definitely won't affect your image.

I got a Polish projection lens - Polkinar 120/1.8 with something like this:

and it works. I mean... not perfectly (yet! - waiting for customized adaptor), but works. I took some samples freelensing, so a lot of light leaks, but it wasn't that bad at all:
http://lenscraze.blogspot.com/2013/11/zk-polkinar-120-mm-118-polish-cinema.html
I believe some lenses have a lot of tolerance for mechanical damage.

Keep calm, it's not fungus Wink

(In your case. I have no idea what's wrong with my Polkinar.)

danfromm · Joined: 04 Sep 2011 Posts: 585

iangreenhalgh1 · Expire: 2014-01-07

Whateveritis....

The lens looks like a great performer, congrats.

I had the Tokina RMC 3.5/200, it was pretty poor, tons of CA and nowhere near as sharp as this lens.

Mir · Expire: 2017-09-30

kido · Joined: 06 Jun 2013 Posts: 105 Location: Chile

David · Expire: 2013-01-25

I have that, though much worse, on my Nikkor-P 105mm 1:2.8. It's where the paint inside the lens barrel didn't adhere to the substrate and became dislodged. It comes off in dots because those are the holiday bubbles formed by poor adhesion. The paint just goes away. I think it just falls off, gets sucked into the mechanism when focusing changes the internal air pressure, and gets lodge or ground up there. I've never had any issues with it working its way back into the lens.

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

ZoneV · Expire: 2011-12-02

Regarding the Schneideritis. Sometimes the black color seems partial no longer attached to the lens - but when I try to get rit of it it was still much work.
In the few cases I examined I found no peeling paint on the back of the lens.

danfromm · Joined: 04 Sep 2011 Posts: 585

[quote="Lightshow"
"idiosyncratic non-standard definition" Thanks for taking it easy on me... I stand corrected, that was what it was called in every forum I found while searching about the Rokkor M 28 ...

Who would have thought the internet would lead me astray? Confused

[/quote]

The Internet was invented to make it easy to lead the innocent astray. Give up your innocence.

More seriously, there's a common language. Or, rather, there was a common language before the Internet became generally available.

Consider, for example, "back focus." Once upon a time back focus was an attribute of a lens, meant the distance between the vertex of the lens' rear element and the image plane when the lens was focused at infinity. Useful concept.

Now back focus describes what a lens and an autofocus system do together. When a maladjusted (old euphemism for crazy) AF SLR or a defective lens focus the lens so that the plane of best focus as seen from the image plane is behind the plane of best focus as seen on the SLR's ground glass, we say the system back focuses or has back focus. Another useful concept, as is its brother front focus.

People talk about point and shoot cameras, film and digital, that back or front focus; I think its better to say that their autofocus systems don't work properly since with them just where the plane of best focus ought to be is hard to see.

We had one good back focus concept, now we have two. The tower of Babel will never be completed.

Lightshow · Joined: 04 Nov 2011 Posts: 3666 Location: Calgary

And Back-focus could have just as easily been used instead of bokeh.
English loves to acquire new words to describe things already described.

Oh, in case it was missed, my comment about the internet was subtle sarcasm.

pd1987 · Joined: 08 Dec 2013 Posts: 74 Location: Poland