Mamiya RB67 extension ring 1: Which lenses fit?

[hsvdg]

Hello,

I recently bought on ebay a Mamiya Extension Ring 1 for RB67. According to the manual, it should fit to most Mamiya RB67 lenses. However, I found that I can only mount the 140mm macro on it. None of my other lenses (e.g. 90mm, 50mm) would fit.

Am I doing something wrong? Do I need to adapt the extension ring somehow to make them work together?

Thank you!

 

[Ian C]

Here is the instruction manual for the RB67 Auto Extension Tubes. Bear in mind that you must cock the mirror before installing onto or removing the tube from the camera. You have to likewise cock the tube’s cocking pins and the shutter. Perhaps this is the step you’re missing.

See “Prior to Attaching the Auto Extension Tube” in the manual.

https://ianbfoto.com/downloads/Mamiya RB67/Mamiya RB67 Extension Tubes non-SD.pdf

 

[hsvdg]

Here is the instruction manual for the RB67 Auto Extension Tubes. Bear in mind that you must cock the mirror before installing onto or removing the tube from the camera. You have to likewise cock the tube’s cocking pins and the shutter. Perhaps this is the step you’re missing.

See “Prior to Attaching the Auto Extension Tube” in the manual.

https://ianbfoto.com/downloads/Mamiya RB67/Mamiya RB67 Extension Tubes non-SD.pdf

H Ian,

thank you for the link. I actually had downloaded it (from your site) before. The issue seems to be the shape of the inner lens element in 140mm vs all others, not the cocking (which I have done). The other lenses simply do not fit onto the ring, whereas the 140mm fits easily.

It is very odd.

 

[hsvdg]

Update: I looked at some photos of these extension rings and understood what the problem is. For example this one:

https://ianbfoto.com/wp-content/uploads/2021/04/14988-4514.jpg

You can see a dark ring around the opening. This ring prevents lenses other than 140mm to attach, I think. Looking at some other pictures.

https://ianbfoto.com/wp-content/uploads/2021/04/18713-3446-600x600.jpg

Here the dark ring is missing.

This dark ring rotates on mine, but I have not been able to simply unscrew it....any advice?

 

[MattKing]

That ring isn't actually part of the extension tube.
It is an adapter that is used between the newer, wider throat camera mount found on the RB67 Pro-SD and the older, narrow throat lenses, in order to make the mount more secure against physical forces.
It isn't strictly necessary to use that adapter, but it is always advisable, when the camera mount - or end of the extension tube - has the wider throat.
Are your 50mm and 90mm lens K/L lenses?

 

[hsvdg]

Thank you for this. Actually, I have a an SD, but use Sekor C lenses. So, this ring is the adapter. I know that Sekor C needs an adapter for RB67 SD, but I have never been able to find out about this.

Is there any way to remove the adapter from the extension tube? Simply unscrewing does not work.

 

[MattKing]

It may just be pushed into where it is - a friction fit.

 

[hsvdg]

Thank you... sorry, stupid question. How do I get it out? I could not do it.

 

[MattKing]

Thank you... sorry, stupid question. How do I get it out? I could not do it.

Usually I've seen them stuck on the lenses - so I don't have a good answer to how to get one out of what is essentially the same as the on-camera mount.

 

[hsvdg]

Update on my own post: After trying a lot and looking at the manuals. It seems I got the NA701/NA702 extension tubes, which are for RB67 SD only, and work (apparently) with the 180mm, 150mm (tried), 360mm and 140mm(tried) C lenses, but otherwise only with the KL (65,75, 90 210, 250, 350). This has to do with the size of the mount.

On my tubes "SD" is not printed, but apparently on some it is.
I assume that there are also extension tubes for Pro/Pro S, but looking at ebay, I am not sure how to identify those. Adverts rarely give the product number.

 

[tosha_gogo]

Update on my own post: After trying a lot and looking at the manuals. It seems I got the NA701/NA702 extension tubes, which are for RB67 SD only, and work (apparently) with the 180mm, 150mm (tried), 360mm and 140mm(tried) C lenses, but otherwise only with the KL (65,75, 90 210, 250, 350). This has to do with the size of the mount.

On my tubes "SD" is not printed, but apparently on some it is.
I assume that there are also extension tubes for Pro/Pro S, but looking at ebay, I am not sure how to identify those. Adverts rarely give the product number.

Hi, I had the same issue where my Sekor C lenses did not fit on the extension tube. This chat helped me to solve the problem.
To fit the extension tube, you need to remove the black rings on the back of the lens.
The inner diameter of the extension tube is 52 mm, while the outer diameter on the lens side is 61 mm.
The black ring can be easily removed with a thin pin. Once removed, the lens can be used without any problems.