There is much confusion when trying to fathom which vintage filter to buy for a Twin Lens Reflex camera that has a bayonet mount such as a Rolleiflex or Yashicamat. The reason is there are three sizes. Rollei Bayonet I Rollei Bayonet II and Rollei Bayonet III. The Bayonet I is sometimes described without the I because there wasn’t a Bayonet II or Bayonet III when it was introduced.

Well wouldn’t it be easy if all filters were marked with Bay-1, Bay-2 or Bay-3? Life’s not that simple!

To make things confusing manufacturers often left off these simple markings on their filters. And to make things even more confusing they added measurements in mm so a Bay-1 filter may be marked 28.5mm, which doesn’t seem to relate to its diameter. And to add icing to the confusion these filters were often renamed B30 or B-30.

So to help here’s our interpretation of the system and an easy way to check if the filter you have found on ebay or in the junk shop, flea market, antique centre, camera shop is the one you need.

Bayonet 1
Also known as: Bay I / B30 / B-30
Outer measurement: 37mm
Inside diameter: 30mm
Sometimes marked: 28.5mm
Fits: Rolleicord and Rolleiflex (with f/3.5 Tessar / Xenar), Yashica EM, Yashicamat, Yashicamat-124, YashicaMat-124G Minolta Autocord


Bayonet 2
Also known as: Bay II
Outer measurement: 41mm
Inside diameter: 34mm
Sometimes marked: 34 or 36mm
Fits: Rolleiflex (with f/3.5 Xenotar and f/3.5 Planar)


Bayonet 3
Also known as: Bay III
Outer measurement: 46mm
Inside diameter: 38mm
Sometimes marked 38mm
Fits: Rolleiflex (with f/2.8 Xenotar or Planar)

Hope this helps clear things up…and if you know different i’m sure you will let us know 🙂

At the time of writing PhotographyAttic has a range of filters for sale in these mounts
Hoya B30 Yellow K2
B30 Pale Green
B30 Pale yellow
B30 Yellow
B30 Yellow Green
Bay II Skylight
Bayonet III Yellow Green
Aico B30 +2 close up lens set
Aico B30 +2 close up lens
Astron Aico B30 +2 close up lens set
Rollei Rolleinar Lens Set 2 28.5mm
Photax B-30 Close up no 3
Unbranded B-30 Close up no 3

You can also buy a Cokin adaptor and use A-series filters. We have the Cokin A to Rollei Bayonet II adaptor here

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