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Adapter ring to mount the Rodenstock 32mm CF (86x1mm) to the Schneider 28XL (86x0.75mm) lens?

The centre filter (CF) E86/105 for the Rodenstock Digaron-W 32mm seems like a possible alternative to the rare Schneider CF IVd designed for the Super-Digitar 28XL lens.

The Rodenstock CF has the advantage of ready availability and uses dyed glass rather than the evaporated metal oxide coating used by Schneider that can produce ghosts in certain lighting conditions.

The native Schneider CF IVd provides 2 stop correction and has a 86x0.75mm mounting thread. The Rodenstock CF E86/105 provides 2.5 stops of correction and has an 86x1mm mounting thread. The lenses they are designed to cover both have an image circle of 90mm.

I'm aware that Schneider recommended that the older CF IVb for the Super-Angulon 72XL (95x1mm mounting thread) be used as an alternative, but perhaps the Rodenstock might work well too.

The big challenge, however, is that the 86x0.75 filter thread on the 28XL lens is located on the outside edge of the lens barrel, rather than on the usual position inside the front edge. Accordingly, the thread on the native CF is located forward of the rear surface rather than rearward. Schneider adopted this unique design, it seems, to bring the CF rearward as far as possible in order to avoid mechanical obstruction of the 28XL's image circle.

Has any forum member found an existing adapter to achieve this mounting? Alternatively, can anyone point me to the adapter ring needed to mount the Schneider 95x1mm CF IVb?

Rod
 
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f8orbust

Active member
Because of the way the S/K CF attaches to the 'outside' of the 28 (which I've never seen on any other lens) I think it would be hard to find an off the shelf solution to adapt a different CF. An adapter like the H&Y Revoring might work because it attaches via friction rather than a thread (but maybe the CF will sit too far forward). That said, machining an adapter for the job should be pretty easy, so I'd get in touch with a shop like SK Grimes.
 
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f8orbust, thank you for both suggestions. The filter threads are right near the front edge, and I think they would interfere with and be damaged by a friction-mounted adapter like the H&Y Revoring. Interesting adapter, though. And regarding SK Grimes, I contacted them regarding a 95x1mm adapter, but paused it when I realised that the Rodenstock CF might be better. That might be the best way forward in the long run, though.

anyone, thank you for pointing me to that eBay listing. For me, the listing says: "This item does not ship to Australia", so that's why it didn't appear in my searches. Now, the listing says nothing about the thread pitch, so I presume it would be the more common 86x1mm on both ends. Is that correct? How well does the adapter mount to the 86x0.75mm thread on the 28XL lens? Does it damage the threads on the 28XL when you do this? How far can the you turn the filter before it stops?
 

f8orbust

Active member
Ignore the picture in this link since it doesn't seem to refer to the actual product described, but if you combined this with the adapter highlighted by anyone, then it should (in theory) work - i.e. anyone's adapter would allow you to mount the R/S CF, and then the adapter I mention here would attach (via the coarse 1mm male thread) to this, leaving an 86mm fine (0.75mm) female thread to attach to the lens. The only problem might be just how far the CF is away from the lens, but given the adapters aren't too expensive it might be worth a punt.
 
The supplier of the female 86x1 to female 86x1mm thread adapter ring linked to by forum member 'anyone' excludes sales to many countries, including Australia and UK.

So far I've been unable to find an alternative source for that ring.

The ideal solution is a female 86x0.75mm to female 86x1mm thread adapter ring. If anybody can suggest a source, please do.

I'm also trying to locate an adapter able to mount the Schneider IVa CF, which has a male 95x1mm thread.

Any further suggestions are most welcome.
 

f8orbust

Active member
I'd probably contact the eBay seller since it says they're in Germany and yet Germany is on the excluded shipping list - along with most other EU countries. Probably the listing is just goofed up since other similar items from the same seller don't appear to have the same restrictions, which makes no sense whatsoever.
 

guphotography

Active member
The centre filter (CF) for the Rodenstock Digaron-W 32mm seems like a possible alternative to the rare native Schneider CF for the Super-Digitar 28XL lens.

The Rodenstock CF has the advantage of ready availability and uses dyed glass rather than the Schneider's metal oxide deposit that tends to ghost in certain lighting conditions.

The native Schneider CF provides 2 stop correction and has a 86x0.75mm mounting thread. The Rodenstock CF provides 2.5 stops and has an 86x1mm mounting thread. The image circles of both lenses are 90mm.

I'm aware that Schneider recommended that the older IVa CF for the Super-Angulon 90XL (95x1mm mounting thread) be used as an alternative, but perhaps the Rodenstock might work well too.

The big challenge, however, is that the 86x0.75 filter threads on the 28XL lens are located on the outside edge of the lens barrel, rather than on the usual position inside the front edge. Accordingly, the threads on the native CF project forward of the rear surface rather than rearward. Schneider adopted this unique design, it seems, to bring the CF rearward as far as possible, in order to avoid mechanical obstruction of the 28XL's expansive image circle.

Has any forum member found an existing adapter to achieve this mounting? Alternatively, can anyone point me to the adapter ring needed to mount the older Schneider 95x1mm IVa CF?

Rod
Hi Rod,

Can I double check that Schneider recommended IVa as an alternative not IVb for 72mm xl?

Thanks
Gu
 
Gu: Can I double check that Schneider recommended IVa as an alternative not IVb for 72mm xl?

Ahh, of course. How did I switch those two? (I have them both). Yes, it's the Schneider IVb CF (95x1mm) that provides the 2-stop correction for the SA 72XL and was recommended (to someone somewhere) as the alternative for the original IVd CF for the Super-Digitar 28XL. I've now corrected the original post. Thank you for pointing out the error.

f8orbust: Yes, I thought the same and have sent a message to the seller. Thank you.
 
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kinglang

Member
CF for HR32 that provides the 2.5-stop correction, CF IVd that provides the 2-stop correction,you will get brighter edges.

Interested about "Rodenstock CF has the advantage", Is there more information, with pictures and examples?

Certain angles of CF IVd cause some reflections, which can be resolved with just a Dinkum CINE Lens Shade . But some angles still have reflections even without CF, see here, https://forum.luminous-landscape.com/index.php?topic=118616.0;nowap
 
kinglang, here's some more information on the Rodenstock E86/105 CF for the Digaron-W 32mm:

Rodenstock explained that the radial-symmetric graduation in neutral density is achieved by a planoconvex lens of grey glass, which is cemented to a matching planoconcave lens of clear glass. Rodenstock claimed that the CF avoids the problem of 'stray light' that is found from 'conventional filters' that use an evaporated metal oxide deposit.

Examined in the hand, the Rodenstock E86/105 CF is impressive and the surfaces exhibit very little reflection. That's part of what prompted me to find a way of trying it as a substitute for the Schneider IVd CF on the Super-Digitar 28XL.

I've attached the original construction drawing and an informative press release from Rodenstock for Photokina (2010?). The original 2MB PDF was too large, so I've uploaded two screen snips, A and B, instead.

kinglang, thank you for both your links. I hadn't seen that particular report of flaring on LuLa. Yes, a flag like that Dinkum Cine Lens Shade will be very handy.

I've only recently changed from 4x5 film to digital for my photography of historic architecture, so as yet I don't have any examples to share of my own. Right now I'm preparing for my first overseas trip since the big spend on the IQ back and digital kit.
 

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"CF for HR32 that provides the 2.5-stop correction, CF IVd that provides the 2-stop correction; you will get brighter edges."

kinglang, Yes, I anticipate that the 0.5 stop difference will result in slightly brighter edges than would be obtained with the 2-stop Schneider CF IVd.

However, Schneider's technical data sheet (attached) for the Super-Digitar 28XL shows that at the working aperture of f/8, the illumination fall-off towards the edge of the image circle amply exceeds 2 stops. From the MTF graphs, the right hand edge of the illumination graph appears to be placed at 45mm, which is the full radius of the specified 90mm image circle. At that point the illumination has decreased to around 12%, or 3 stops. On this basis, if the Rodenstock E86/105 CF is used, the edges of the image circle would still be darker than the centre, but somewhat less dark.
 

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taada

New member
Fun fact:
The comparison shots in the Rodenstock leaflet were taken on the street in front of Alpa's headquarters in Zurich. I saw these pictures and thought, I know that place! A short trip using Streetview confirmed this (Neptunstrasse 96, 8032 Zurich).
 
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