What is the purpose of these rings??

[tonyowen]

Attachment 137939 Attachment 137941

The two rings shown on the above images were supplied with a Krokus 69 Colour S enlarger – but I’ve no idea as to their purpose.

Silver ring has three tapped holes THAT ARE NOT EQUI-SPACED.
Uncertain as to whether the screws are fitted as shown or whether they show be screwed from the back.
There is a ‘zero dot’ close to one of the tapped holes
The centre hole is not threaded.
The external periphery of the ‘black ring’ on the reverse side IS NOT threaded.
All screws are fitted with lock-tightening material.

The Smaller ring has three tapped holes fitted with slot headed ‘grub screws’.
Adjacent are three countersunk clearance holes.
The hole is M32 thread – which is identical to that on my Componon-S enlarging lens
All grub-screws are fitted with lock-tightening material.

General
Although this was provided with the enlarger, the two rings (assuming they are a pair) offer the possibility of tilting a lens – much as the objective of a telescope can be tilted to provide correct alignment. Also the fact that the smaller ring can only be fitted in one radial position infers a precision that would appear to be unnecessary for enlarging!!

Any ideas would be welcome.

Regards
Tony

[Jim Noel]

They are lens mounts for a Durst, or similar, enlarger.

[tonyowen]

They are lens mounts for a Durst, or similar, enlarger.

Thank you.
Can you please elaborate as to their purpose and how they are used - the need for the possibility of super-fine adjustment alludes me.
Also why might they be provided when I bought the Krokus in the 1980s???

regards
Tony

[Drew Wiley]

They're not Durst rings, just analogous. Sizing adapters for various lenses - have no idea what kind. You've already spotted an adjustment tweak. The threaded 32mm one has obvious common applications. Otherwise, I've never even heard of Krokus.

[Bob Salomon]

They're not Durst rings, just analogous. Sizing adapters for various lenses - have no idea what kind. You've already spotted an adjustment tweak. The threaded 32mm one has obvious common applications. Otherwise, I've never even heard of Krokus.

Kook us is a Polish enlarger manufacturer. Similar to Meopta.

Sorry, Krokus.

[tonyowen]

Kook us is a Polish enlarger manufacturer. .

You're correct [Krokus] and they are very well built and rugged - no plastic and flimsy parts.
However, I've found a mention that shows the three point adjustment system is not unknown for enlargers:-

" The Beseler 23s are nice enlargers... but the lens stage alignment system is so damn (useless, in practice).If yours came with the "normal" lens board (and bellows), you`d be better looking for the adjustable type, third party unthreaded ones. This lens boards will let you to properly adjust the lens stage; they have two plates, connected by three adjustable screws. If you like sharpness, enlarger alignment is a must, there is no other route. "

regards

Tony

[dsphotog]

Looks like a custom modified durst lens board.

[mpirie]

The one on the left is a Durst L1200 or L1000 lens mount that's been customised to take adapters like the one on the right.

From memory, the left one should be around 78mm diameter. They come as flat or recessed panels for lenses from 25mm to 52mm mounting diameter.

Mike

[Ginette]

This is an ajustable Durst Lapla.
Durst did thoses in many sizes and recessed like their standard Lapla.
The 2 parts you have are disassemblied and probably roughly sanded.
Here one. You can see the screws from top and bottom.
You have a black dot point on the mount to position the lensboard always at the same place once the lensboard is perfectly leveled.

[Luis-F-S]

This is an ajustable Durst Lapla.

+1 exactly what they are. L