M-Rokkor 28/2.8: Spots, Schneideritis, Haze - How can I decide, what's what?

[krötenblender]

Originally Posted by hexiplex

Do you know if the white spots have a tendency to return after service?

No, can't say anything about that. But if they return, I will post.

Originally Posted by hexiplex

Thank you for remembering to share your experiences by the way!

I promised...

[krötenblender]

Originally Posted by back alley

big difference in the looks of the lens...very curious to see what the difference in images might be like.

Well, it's not that much of a difference. As I wrote before, I had a small foggy spot in the center of the image, which is gone now. But the lens was good before, so I expect only small differences, like improved contrast and less flares. Since I really like that lens, I think, it was worth the money.

[back alley]

the rokkor 28 is a great lens...i sometimes think of looking for a good copy so i might have a faster 28 than the cv 3.5 but one that is still just as small.

[krötenblender]

Originally Posted by Daan

just curious, but did he also change the mount of the lens so that the right framelines come up on a M?

Of course not. It's the same lens as before.

[haempe]

Got this week my CLE with 28/2.8 back from Will van Manen.

CLE got CLA; new light seals, "flickering LED syndrome" repair...
Rokkor: white spots removed; mount changed to bring up the 28mm frame at the M



Unfortunately, a previous owner clean the coating off the frontlens...

[kermaier]

I had the spots in mine repaired by John Van Stelten at FocalPoint in the USA. It was great for a while, but then the lens developed haze in the front element group. DAG was not able to completely clean it out (but he did modify the mounting flange to bring up 28/90 frame lines on a Leica M camera, as well as mill 6-bit coding into it). The haze results in flare when pointed toward the sun, and maybe a bit lower contrast overall.

I don't really use the lens anymore since buying an Elmarit-M Aspherical 28/2.8, but in some ways I liked the M-Rokkor better.

::Ari

[micromoogman]

Anyone knows where these bubbles develop? Is it between a glued lens group or just on the surface of one element? If it's not in between it might be worth trying doing it yourself. Got one for $300 5 min ago and I must do something even if pics come out good...

[Palaeoboy]

Originally Posted by micromoogman

Anyone knows where these bubbles develop? Is it between a glued lens group or just on the surface of one element? If it's not in between it might be worth trying doing it yourself. Got one for $300 5 min ago and I must do something even if pics come out good...

The front glass of the Rokkor 28 is a single element so its not a glue or separation problem. The white spots are crystals that leech out of the black paint that coats the side rim of the element painted on to reduce internal reflections. Thats why the appear as a perfect circle around the lens when you look at it straight on. The process is accelerated by heat. The crystals can continue to form until they break off and find their way onto the inner surface of the front element whereby they can etch into the lens coating itself. Not all go that far. Most never get past the rim which has little effect as its not in the optical path. Its fixable but the hard part is that the front element is difficult to remove from the element tube. It may be more than a do it yourself job.

[raid]

Originally Posted by kermaier

I had the spots in mine repaired by John Van Stelten at FocalPoint in the USA. It was great for a while, but then the lens developed haze in the front element group. DAG was not able to completely clean it out (but he did modify the mounting flange to bring up 28/90 frame lines on a Leica M camera, as well as mill 6-bit coding into it). The haze results in flare when pointed toward the sun, and maybe a bit lower contrast overall.

I don't really use the lens anymore since buying an Elmarit-M Aspherical 28/2.8, but in some ways I liked the M-Rokkor better.

::Ari

Ari: Wasn't your lens without the white spots at first?

[kermaier]

Originally Posted by raid

Ari: Wasn't your lens without the white spots at first?

It had a variation on the white spots theme: translucent spots in a similar uniform pattern. John at FocalPoint said the cause is the same -- condensation interacting with metallic compounds in the coatings to produce crystalline bubbles.

I'm still planning to send it back to John to see if he can get rid of the garden-variety haze it currently has. Then I'll have to decide which of the M-Rokkor and the Elmarit-M stays and which goes....

Cheers,
Ari

[micromoogman]

It so strange that this phenomena doesn't affect the image. Are these spots visible if you let the light come through the lens and get focused on a white paper? They must be visible at some point of focusing distance...not necessarily within the range in the camera. Also worse with small aperture?
Might it be possible to keep the front glass in the barrel and clean it from the inside? Dismantle aperture blades and the other lens groups. Just thoughts...

[astro8]

Originally Posted by micromoogman

Might it be possible to keep the front glass in the barrel and clean it from the inside? Dismantle aperture blades and the other lens groups. Just thoughts...

I thought of doing that but it looked easier to cut the front element out.

[Palaeoboy]

Originally Posted by micromoogman

It so strange that this phenomena doesn't affect the image. Are these spots visible if you let the light come through the lens and get focused on a white paper? They must be visible at some point of focusing distance...not necessarily within the range in the camera. Also worse with small aperture?
Might it be possible to keep the front glass in the barrel and clean it from the inside? Dismantle aperture blades and the other lens groups. Just thoughts...

I think your misunderstanding where the spots are in the early stages. They are not on the optical front and rear of the element, they are on the side of the element which is painted black to prevent internal reflections. They are visible because of the way the sides are angled that permits you to see them as a ring. But in the early stages its not on the optical path and therefore doesnt have any impact on image quality. In the later stages however the crystals break off and then find there way onto the rear surface of the front element. Its at this point it does affect lens performance and can etch into the multicoatings of that element. For some reason only a few get to this later stage. Maybe the paint where the crystals leech from was applied thinner so there isnt enough to create large enough crystals to get to the damaging phase. The phenomenon is not unique to this lens. I have photos of Schnider, Zeiss Hologon and Elmarit lenses that have had the same problem, its just the instances with the Rokkor are more frequent.

[micromoogman]

Thanks for clarification. I have those bubbles on a Zuiko 50/1.4 too, but those are clearly limited to the outer region of the lens element/group, these are all over. These also look more like micro spots than transparent bubbles.
Shouldn't every "bubble" create a lens in itself, changing the path of the rays of light?

[raid]

My Rokkor has very few white spots. In fact, I sold the lens at RFF as not having any white spots, but the buyer sent the lens back because he found white spots. I am a very happy dude that I got my lens back. On the EP-2, it is a normal lens with 2.8 max aperture.

[JohnTF]

I had one I had bought new, accidentally -- it was shipped in a 40mm box, and my local shop gave it to me for the price of the normal lens with the CL kit I was buying.

I had it for years, and as I recall, the white spots appeared in a much reduced form.

I was told it was not repairable, and sold it on at a reduced price to a happy dealer, I probably should have tested the performance, but we are kind of hard wired to see any defect in a lens to be, perhaps, more important than the subject and the guy behind the camera.

At shows, people always want lenses and bodies to be pristine in looks, even above function.

My local shop knew I was looking for an M2 user, and took one in trade with scratches on the body and a hazy lens, they did not even ask, just shipped it to me for the trade in price,-- they did not want in in the shop-- new customer wanted to trade.

I got the lens cleaned, turned out to be a simple job, and found the camera had been CLA'd and had the M4 frames installed, all for a highly reduced price mostly because the PO had scratched up the top mainly from installing and removing the meter. Yeah, it has a few "experience" marks and a slight ding.

If I pull one out to use, this is a good choice.

I'll make up a different story if I put it up for sale.

And, now, I would not have sold the 28mm Rokkor, more hind sight?

-- OTOH, got a good deal on the CV 28, some wear showing, so got it right, with adapters and M8 UV filter--

BTW, Looks like a nice cleaning job, nice of you to keep things posted on the long term.

Raid, glad you got it worked out right.

Regards, John