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Question: Robot screw mount lenses: different thread sizes?
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PostPosted: Mon Jan 08, 2018 7:26 pm    Post subject: Question: Robot screw mount lenses: different thread sizes? Reply with quote

I was hoping someone with a bit more experience (and knowledge) can chime in on my issues with my Robot-lenses.

I currently have 3 Robot screw mount lenses, 1 robot camera (btw are these cameras amazing!!!) and 2 Robot-FX adapters.

The strange thing is, 1 lens will mount the camera and adapter 1. The other 2 lenses will only mount adapter 2.

Some sources refer to Robot 25mm screw mount, while others specify Robot 26mm screw mount.

Have there been different thread sizes through the years? There is no visible damage on the thread of any of the lenses, adapters and camera mentioned. (I cannot find my thread gauge so cannot measure myself with certainty...)
Or do you suspect there is indeed some damage at play?

I ask this, because I'd like to convert the Robot-mount to LM (or LTM) with parts I select myself, instead of based on an add simply stating "Robot screw mount" and which will at best mount part of my Robot-lenses. (On my Fuji, these lenses are actually too small for comfort, but on my GXR, they would look and balance much better, therefor the idea for conversion to LTM or LM mount)


PostPosted: Mon Jan 08, 2018 9:06 pm    Post subject: Reply with quote

There are two different mounts for Robot cameras. The old version is M 26 x 0.75 mm and the newer version changed to M 26 x 1 mm. Flange focal distance is 31 mm for both versions. There are ready adapters cheaply available from Robot to LTM on Evilbay. Most probably for the newer mount version (they don't state which version is supported).


PostPosted: Mon Jan 08, 2018 9:12 pm    Post subject: Reply with quote

I too have seen references to 25mm and 26mm threads for ROBOT lenses but all of the dozen or so ROBOT lenses I have owned over the years have fit properly in every adapter I have owned.

I pulled out my old Focal Press "The Camera Guide" for the ROBOT camera (second printing, June 1950) and it doesn't mention anything about differing threads.


PostPosted: Mon Jan 08, 2018 9:23 pm    Post subject: Reply with quote

Thanks Thomas! This helps a lot!

With the specs, I suppose I can get correct 26mm >> 39mm rings (or improvise some contraption) and some spacers to get it to the correct register distance. Also it makes it easier to make a close-up-adapter as well for these lenses. Besides, with this approach, I can (in theory) also adapt the lenses to other camera-mounts (e.g. though a 26mm >> 42mm step-up-ring) So in short, I'm in the mood for some tinkering Smile This is new territory for me, this is a simple mount to start with, and the issues with my current adapters add some motivation.


PostPosted: Mon Jan 08, 2018 9:25 pm    Post subject: Reply with quote

newst wrote:
I pulled out my old Focal Press "The Camera Guide" for the ROBOT camera (second printing, June 1950) and it doesn't mention anything about differing threads.
Maybe the 2nd thread is post-1950, or on the contrary, so old that it is not mentioned in a 1950-book Question

1 thing is for sure, my SK 37.5 will fit adapter 2, but not my Robot-cam and adapter 1; my Biotar 40 will fit cam and adapter 1, but not adapter 2.


PostPosted: Mon Jan 08, 2018 9:39 pm    Post subject: Reply with quote

Like I said before, I have owned about a dozen different ROBOT lenses, from those designed for the first ROBOT 1 models to much later, post-war coated models and even a Prakticar version custom produced in Romania for use by their security services. All of them have been compatible.

Berning did produce a different mount lens for their final ROBOT Royal series but it wasn't a normal screw mount, it was an Interrupted Screw design, similar to those used on the breach blocks of military canons. That mount was so different from the standard thread mount you would see it immediately and wouldn't need to ask if it was a different mount.

I've been studying ROBOT cameras and lenses for at least five years and have never seen any reference to the company changing the screw mount. I would bet my money rather on something being wrong with your lens.


PostPosted: Mon Jan 08, 2018 9:40 pm    Post subject: Reply with quote

Well, I have the information from the German site www.robot-camera.de. I think they should know.
Maybe you can use Google translate to read it yourself.
It's also stated there that the old lenses can be used on the newer cameras but not the other way round.
BTW, obviously there was also a Robot with bayonet mount.


Last edited by tb_a on Mon Jan 08, 2018 9:49 pm; edited 1 time in total


PostPosted: Mon Jan 08, 2018 9:46 pm    Post subject: Reply with quote

Thanks, reading in German is no problem, I was just stupid and forgot to google with German search terms (my technical german is a little limited in my active vocabulary, although I can read it just fine)

I will have lots of fun reading this site!