Schneideritis?

[John Conway]

I'm curious if anyone has ever had a Schneideritis lens reconditioned.

[BrianShaw]

I'm curious if anyone has ever had a Schneideritis lens reconditioned.

When I last spoke to the Schneider west coast (US) repair center, the position they maintained is that there was no reason to do so... and no warranty support even if one wanted it done. I never asked how much a repair would cost or how effective such a repair would be, though.

[hoffner]

As for me... I've only looked at Schneideritis from the front of my lenses when setting the shutter so my theories are extremely limited.

As anyone else - how otherwise would we look at the defect? It is even impossible to see through the lens edge because, obviously, the edge is ground (very rarely polished). Unless you want to disassemble the poor lens to have a look at the detached paint from the outside, which, of course is out of question for obvious reasons.

The Schneiderits is a problem of paint flaking off (for whatever reason) the lens ground edge. It is there it was applied and not on the barrel material.

[BrianShaw]

... Unless you want to disassemble the poor lens to have a look at the detached paint from the outside, which, of course is out of question for obvious reasons. ...

But destructive analysis is sometimes required to accurately/completely understand a failure mode. That is why I ask the same question that Dan asks.

[hoffner]

I understand, Brian, but that is not the OP's intention.

[Leigh]

In the few lenses that I've seen, there were multiple defects spanning a range of distances from the front of the barrel.

Given that these are on an angled surface, as the barrel diameter decreases toward the shutter, they were obviously on the inner surface of the barrel, NOT a defect on the element edging.

BTW, given that the element edging is black, and the barrel in which the elements are mounted is also black, how would we see an edging defect in the first place?

- Leigh

[BrianShaw]

I understand, Brian, but that is not the OP's intention.

Agreed... and it does not appear to be anyone else's intention either. I understand that. Jus' sayin'

[hoffner]

In the few lenses that I've seen, there were multiple defects spanning a range of distances from the front of the barrel.

Given that these are on an angled surface, as the barrel diameter decreases toward the shutter, they were obviously on the inner surface of the barrel, NOT a defect on the element edging.

- Leigh

Schneideritis defect is independent of the angle of lens surface it is created on.

BTW, given that the element edging is black, and the barrel in which the elements are mounted is also black, how would we see an edging defect in the first place?

- Leigh

For the answer see the post n. 27

[Leigh]

Schneideritis defect is independent of the angle of lens surface it is created on.

How many lens elements have beveled edges so they can be mounted in a conical assembly?

Elements have cylindrical edges, and are mounted in cylindrical structures that have tight tolerances.
This is necessary for the element optical axes to remain aligned during the life of the lens.

Even if the edge paint did come off, there's no place for it to go since there's no clearance.

While your assertion about edging may be correct in some instances, it is definitely not correct for all, and
definitely not for the instances that I observed.

For the answer see the post n. 27

The argument presented in #27 is totally specious.

If the air/glass surface reflected enough light for the image to be prominent, the on-axis reflections would be high enough that no light would reach the film.

Disregarding that fact, the edge finish of an element is not smooth.
How could it reflect an image that was in sharp focus?

- Leigh

[hoffner]

How many lens elements have beveled edges so they can be mounted in a conical assembly?

Elements have cylindrical edges, and are mounted in cylindrical structures that have tight tolerances.
This is necessary for the element optical axes to remain aligned during the life of the lens.

Even if the edge paint did come off, there's no place for it to go since there's no clearance.

While your assertion about edging may be correct in some instances, it is definitely not correct for all, and
definitely not for the instances that I observed.

- Leigh

Lens elements have many types of edges - bevels, chamfers, break edges are utilized.

Flaking of the edge paint ((be it due to outgassing, paint ageing, its thermal expansion/contraction, glass thermal stress or yet other reasons) can take place on a micron scale, even a fraction of it only. That is more than enough for the incoming ray to encounter a glass/air surface instead of the glass/paint one and change its bending properties. The "space" can be created by the paint contraction but not necessarily. Modern resin based paints used in the optical industry (as opposed to blackening inks) are so thick (again, on a micron scale) that more than often its thickness must be accounted for in barrel mechanical tolerances. Remember - a few microns or even its fraction is what it takes to accommodate the air space that changes the bending index for the rays optical path.

The argument presented in #27 is totally specious.

If the air/glass surface reflected enough light for the image to be prominent, the on-axis reflections would be high enough that no light would reach the film.

Disregarding that fact, the edge finish of an element is not smooth.
How could it reflect an image that was in sharp focus?
- Leigh

Why don't you give the answer at this question you yourself when you think, it is a barrel imperfection that is somehow seen? Why did you not answer the questions the posts n.29 and n.30 asked you?

When it comes to the sharp image you see in Schnederitis the reason of it is exactly the fact, that the ray is deviated by the glass/air surface (notice the correct order of materials) of the lens element's edge and not something behind it, as you and Nathan think. That also explains why the defect is often seen as having silvery appearance like bubbles in water.

That being said, I would like to reiterate the question aimed at you in the n.29 and n.30 posts at which neither you or Nathan gave an answer.