Troubleshooting/Advice: Schneider-Kreuznach 10mm lens (Arriflex Cinegon)

[Iolo Edwards]

There seems to be a problem with my Schneider-Kreuznach 10mm lens for Arriflex ST. Whenever I've used it it's produced a cloudy/fogging image (see image) - this happens whether I use a matte box or not. I enquired with one lens servicing/repair company here in the UK and they suggested that the doublet elements might have separated, if this was indeed the case, they quoted £450 to fix it.    If it was an issue with the coating, however, they said that couldn't be fixed by them. I should say that they were going by the pictures i sent and didn't have the lens itself to inspect.

Anyway, what's your advice regarding this? £450 sounds a great deal of money to spend on the lens, especially considering you can buy another one for less than that. What should I do? Any suggestions? It would be a shame for the lens to simply not be used anymore.

 

[Dom Jaeger]

That sort of fogging is usually due to a severely fungus ridden optic, or some other sort of coating damage/residue. Or deterioration of the glue in a doublet, as mentioned. You could spend some money having it disassembled to have a more accurate diagnosis, perhaps it’s something that may clean off, but it may also be money down the drain if it turns out to be difficult to repair. 

I recently serviced a Switar that was almost opaque due to one internal element being very hazy, which happily cleaned off without too much coating damage, and I’ve encountered such things before, so it is possible your lens could be salvaged for less than half what you’ve been quoted. But I’ve also encountered a lot of lenses that weren’t worth the expense to repair. In the end you have to make the call.
 

[Simon Wyss]

From experience with Schneider lenses I tend to assume grease or oil parts of grease have crept down an element. It only takes a well warm summer day. A quote based on photos is no serious offer.

[Iolo Edwards]

7 hours ago, Dom Jaeger said:

That sort of fogging is usually due to a severely fungus ridden optic, or some other sort of coating damage/residue. Or deterioration of the glue in a doublet, as mentioned. You could spend some money having it disassembled to have a more accurate diagnosis, perhaps it’s something that may clean off, but it may also be money down the drain if it turns out to be difficult to repair. 

I recently serviced a Switar that was almost opaque due to one internal element being very hazy, which happily cleaned off without too much coating damage, and I’ve encountered such things before, so it is possible your lens could be salvaged for less than half what you’ve been quoted. But I’ve also encountered a lot of lenses that weren’t worth the expense to repair. In the end you have to make the call.
 

Thanks Dom. The funny thing is that the glass looks clear of fungus or anything else, but obviously something's wrong. I tend to think it's probably not worth the expense.

[Iolo Edwards]

7 hours ago, Simon Wyss said:

From experience with Schneider lenses I tend to assume grease or oil parts of grease have crept down an element. It only takes a well warm summer day. A quote based on photos is no serious offer.

Thanks Simon. Good point, it's very difficult for them to quote without inspecting it.

[Todd Pinder]

On 1/3/2022 at 1:37 AM, Dom Jaeger said:

I recently serviced a Switar that was almost opaque due to one internal element being very hazy, which happily cleaned off without too much coating damage, and I’ve encountered such things before, so it is possible your lens could be salvaged for less than half what you’ve been quoted. But I’ve also encountered a lot of lenses that weren’t worth the expense to repair. In the end you have to make the call.
 

Hey Dom, just curious what you use to clean stubborn haze? I have a 50mm f1.8 Yvar with some haze on the rear element simple cleaning wouldn't take care of. Cheers

[Philip Forrest]

Cerium oxide paste is what I use to refurbish lenses. It'll take all haze off, with the exception of etched glass that looks like it's been sandblasted. Get the kind used to polish, not cut, telescope optics. 

Phil Forrest

[Dom Jaeger]

I've used a few different things to try to clean stubborn haze. I always start with isopropyl alcohol, then cleaning fluid, and then acetone (be careful of painted boundaries). If they don't work, I have a Zeiss fungus cleaner that is excellent (it contains a fungicide and something else I can't identify that makes it brown), I leave it on for half an hour and it often cleans off haze as well as fungus. I have also tried MEK (don't breathe it in!) and as a last resort I have a very fine polishing paste that is usually OK on modern coatings. 

But often if the coating is damaged, you can't repair it, the element needs to be polished back and re-coated (by specialist companies) or left as is.

 

 

[Dom Jaeger]

On 1/3/2022 at 11:03 PM, Simon Wyss said:

From experience with Schneider lenses I tend to assume grease or oil parts of grease have crept down an element. It only takes a well warm summer day. A quote based on photos is no serious offer.

Proper lens helical greases are formulated so they do not easily separate. I have never seen oil leach onto optics from Zeiss or Angenieux or Cooke factory greases for example. I don't recall seeing oily optics in Schneider lenses, but I don't know what grease the factory may have used back then and it's always possible that people have re-greased a lens with a different sort of grease.

I have seen oil on other vintage lenses, usually the optical surfaces on either side of the iris, which are often the only surfaces open to the outside, but that is often accompanied by oil on the iris blades too. In my experience if there is oil on an optic you can usually see it around the edges (it looks a bit like seperation), or in a circle in the very centre where it has pooled. 

[Simon Wyss]

Right you are. I was exaggerating from a couple of Schneider of which I’m not certain whether they were still in original state or not. Two Wollensak Cine Raptar 25-1.5 I also had to free from oily mist on the glass and sticky grease on the iris.