Dent on Mamiya Rb67 50mm lens normal?

Alex Foo · Jun 23, 2010

Hi all, I just received a 50mm Sekor C lens for my Mamiya RB67 from ebay. It was supposed to be 'new in box'. Upon inspection of the back of the lens, there is what seems like a dent on the back barrel which covers the lens. Is this normal?

The reason I'm asking this is because I don't remember my 127mm lens has that dent. :confused:

Well, this isn't my lens but the dent is like how it is in the picture.

Anyone who owns the lens can confirm this? Thanks

david_mizen · Jun 23, 2010

yes if the oreintation of the barrel is not correct the mirror hits the lens on its way up (or down) when the the lens is focused to infinity(?) (all the way in) my technician has just been through this issue with an ebay lens some one had played with the rear lens element had been removed and reinstalled out of position, the mirror was hiting the element and throwing the shutter out of phase the "flat" is needed to clear the mirror.

Alex Foo · Jun 23, 2010

That's some pretty good info there david, thanks! The mechanical movement of the mirror must be pretty precise and constant cause the 'dent' seems quite shallow. Would there be a chance that the lens might be screwed in just slightly off, and causing the mirror to hit it? I'm hoping that even if the lens is slight off, there is enough leeway for the mirror to flip. Won't wanna hear a crack when the shutter is pressed!

domaz · Jun 23, 2010

Wow a lot of brassing for a "new in box" lens. Perhaps he meant the lens was actually "in a new box"?

Alex Foo · Jun 23, 2010

Lol good one there domaz. Uh, the lens in the pic isn't mine. But i did notice so small scratch on the lens cap which makes me to believe that its just mint condition sold as new. Ugh, nvm that I'll try out the lens on a roll of film and see, or maybe like you said... 'in a new box'. orz

Well I got some external feedback that the dent might be abnormal. Anyway, I wrote to Mamiya just to clear things up since they made the lens. Hope they reply to my mail and I'll update any findings here.

Jeff Kubach · Jun 23, 2010

Looks like my one!

Jeff

Alex Foo · Jun 23, 2010

Hehe Jeff you mean the lens or the dent? =p

Jeff Kubach · Jun 23, 2010

Both!

Jeff

Alex Foo · Jun 23, 2010

Lol, i kinda got this pic off the internet. Can't seem to find it now. Mayb it is?

david_mizen · Jun 24, 2010

it seems only to be an issue on the wide angle lenses where the rear element projects into the camera body and then only when focused to infinity (ie when the bellows is racked all the way in) on the other lens i have the rear element is inside the barrel of the lens and never gets near the mirror

Alex Foo · Jun 24, 2010

When you explained to me, I thought it to be plausible, maybe the wide angle lens needs its back element deeper inside thus the dent there to avoid the mirror hitting it.

I went over to Mamiya site to look at the lens pic, it's pretty small, but if you see close enough, you can actually see the dent there, lol.

ContaxRTSFundus · Jun 24, 2010

As everyone has said, the 'dent' is a design feature to ensure internal clearance of the rear element assembly.

The way the lenses are secured to the camera body guarantees that the lens will sit correctly on the RB or RZ bodies and there is no risk of the mirror accidentally catching the rear assembly of the lens. Of course, if you use this Sekor C 50mm on the RZ67, you have to move the bellows forward by 7mm so even less of a problem. By comparison, if you look at the mount of the RZ's Sekor Z 50mm, it's totally different and the rear element assembly is noticeably more shallow.

Alex Foo · Jun 24, 2010

Thanks for further explaining on it. Now me, or any future owners if any, will know that the dent is intentional and purposeful.

Btw guys, there is a black ring adapter thingy that came along the lens box. It seemed as if it would wrap around the back lens assembly. I couldn't find it's usage in the 'manual'. My guess is that it's for usage on other bodies e.g. RB67, proS or even RB67. Any ideas on it?

MattKing · Jun 24, 2010

Alex Foo said:
Thanks for further explaining on it. Now me, or any future owners if any, will know that the dent is intentional and purposeful.

Btw guys, there is a black ring adapter thingy that came along the lens box. It seemed as if it would wrap around the back lens assembly. I couldn't find it's usage in the 'manual'. My guess is that it's for usage on other bodies e.g. RB67, proS or even RB67. Any ideas on it?

It's probably the adapter that fills the extra space in the lens mount throat on an RZ67 or RB67 Pro SII/D.

ContaxRTSFundus · Jun 25, 2010

Alex Foo said:
Thanks for further explaining on it. Now me, or any future owners if any, will know that the dent is intentional and purposeful.

Btw guys, there is a black ring adapter thingy that came along the lens box. It seemed as if it would wrap around the back lens assembly. I couldn't find it's usage in the 'manual'. My guess is that it's for usage on other bodies e.g. RB67, proS or even RB67. Any ideas on it?

It is for exclusive use with the RB67 ProSD and as was said, it compensates for the slightly wider mount on that model.

Alex Foo · Jun 28, 2010

Thanks guys, I went back and checked the proSD indeed has a wider mount, and plugging the ring in will enable to lens to mount on the camera snugly. ( I din notice it and mounted the lens directly on the camera without the ring, I'm sure it wouldn't hurt the lens or the camera this way, just mayb it will be more prone to vibration or very minor misalignment.)

Oh btw, mamiya replied me in a very straight-to-the point kinda way: That is part of the design.
That's it, the whole email, lol.

Dent on Mamiya Rb67 50mm lens normal?

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