ZUNOW 5cm F1.1 — The Mystery of the 54.5mm and 55mm Filter Threads
Updated: 2 days ago
A Small Difference with an Interesting History
When we first explored accessories for the legendary ZUNOW 5cm F1.1 in 2023, we believed that the earlier versions generally used a 55mm filter thread, while later examples used 54.5mm.
Further research has shown that the story is considerably more complicated.
Through examining surviving ZUNOW lenses, comparing serial
numbers, and studying their mechanical differences, Old Lens Junkies has discovered that filter thread diameter cannot reliably be determined by production period or external appearance alone.
The difference may be only 0.5mm, but for collectors and photographers attempting to fit a filter or lens hood, it matters enormously.
The 55mm ZUNOW
One important example in our collection is ZUNOW 5cm F1.1 No. 5313, a silver Nikon S-mount lens.
This particular lens has a confirmed 55mm filter thread.
Interestingly, it also carries both Teikoku Kogaku and ZUNOW markings, making it especially valuable for studying the development of early ZUNOW lenses.
At one point, we believed that this specification might be typical of the earlier production period.
However, subsequent discoveries challenged that assumption.
The 54.5mm Discovery
Another remarkable example is ZUNOW 5cm F1.1 No. 6136, a later Ping-Pong configuration.
Despite its later serial number, its filter thread has been confirmed as 54.5mm through the fitting of a Tiffen 54.5mm filter.
Our own ZUNOW Eyemo 5cm F1.1, No. 3570, also has a 54.5mm front thread.
Furthermore, our Leica screw-mount ZUNOW No. 6152 uses the 54.5mm specification.
These examples demonstrate that the relationship between production sequence, exterior configuration, and filter thread dimensions is not straightforward.
Why This Matters
The difference between 54.5mm and 55mm may appear insignificant.
However, forcing an incorrectly sized filter or step-up ring onto an extremely rare vintage lens can damage its original threads.
This is particularly concerning with ZUNOW lenses, where replacement components are exceptionally difficult to obtain.
At Old Lens Junkies, we therefore recommend confirming the actual filter thread dimensions of each individual lens rather than relying solely on its serial number or appearance.
From Research to OLJ Type Z
These discoveries have directly influenced our development of OLJ Type Z, a dedicated lens hood project for the ZUNOW 5cm F1.1.
Our initial development focuses on the 54.5mm thread specification, with the objective of creating a practical and aesthetically appropriate accessory for these historic lenses.
Unlike our solid-brass OLJ Type 2, the Type Z is being explored in precision-machined aluminum.
The project remains under development, and compatibility will need to be verified against individual lens configurations.
We are also exploring dedicated OLJ LUX filters for the uncommon 54.5mm specification, including protective and ND filters.
Continuing the ZUNOW Research
The ZUNOW 5cm F1.1 remains one of the most fascinating Japanese high-speed lenses of the 1950s.
Its numerous mount configurations, external variations, engraved markings, and mechanical differences suggest a more complicated manufacturing history than previously documented.
By recording serial numbers, photographing individual examples, and examining their construction, we hope to gradually build a clearer understanding of these remarkable lenses.
Our research is ongoing, and new evidence may lead us to revise earlier conclusions.
If you own a ZUNOW 5cm F1.1, we would welcome information about its serial number, mount configuration, filter thread diameter, and any unusual mechanical features.
Every surviving example may help reveal another piece of ZUNOW history.
Old Lens Junkies — Embracing the Timeless Charm of Vintage Lenses!
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