DOF ring misaligned on RB67 65/4.5 C lens

Theo Sulphate · Jan 12, 2016

Ten days ago I bought an RB67 65mm f/4.5 C lens and foolishly just discovered its DOF ring is misaligned to the right. It's an annoyance, but shouldn't affect anything optically.

Basically there are three red alignment marks on this lens: the triangular mounting mark, the aperture/shutter selection dot, and the focus dot (this lens has a floating-element focus ring). All three red marks are supposed to be in a straight line when the mounted lens is viewed from above.

Looking straight down at the floating-element focus ring - at the extremes of its travel, both the infinity mark and the 3.3m line will align with the red aperture/shutter dot. That indicates the ring is not misaligned - however, the distances on that ring are supposed to be aligned with the much closer red dot in the DOF ring so that you can set the focus and read DOF. That's where my problem is because the dot and all the markings on the DOF ring is shifted to the right by about 1cm. It's as if the DOF ring had been removed and not put back correctly.

It's too late to return the lens or get any money back, so I'm thinking there must be an easy way for this ring to be removed and realigned, but it certainly doesn't twist off. Would the front element need to come off first?

Xmas · Jan 12, 2016

Hi Theo

The ring which rotates withe the infinity and 1m calibration is dual purpose it is the floating element control ring.
It needs to be set up on an optical bench with a microscope if the lens has been dismantled and adjustments disturbed.
Mine needs to come apart but not tried yet.

Noel

paul ron · Jan 12, 2016

the 65 c doesnt have a floating element as far as i know. not sure if there were any varients that did.

the dof ring does absolutely nothing, its a calculator. if you take out the name ring in the front of the lens, you'll see 3 screws that holds the ring in place. you can take the screws out n rotate the ring to align, the set it in with the screws.

id be interested to see a picture of this lens?

Xmas · Jan 12, 2016

Hi Paul

The early 65mm did not have a floating element the 2nd generation ones did, mine does.

Trail Images · Jan 12, 2016

+ 1.....

Xmas said:
Hi Paul

The early 65mm did not have a floating element the 2nd generation ones did, mine does.

Hey Paul, both my C 50 & C 65 have the floating elements......

Xmas · Jan 12, 2016

The pre C 65mms have a conical front section the C are cylindrical?

Theo Sulphate · Jan 12, 2016

Here are some photos of the lens and the misaligned DOF index.

Trail Images · Jan 12, 2016

Xmas said:
The pre C 65mms have a conical front section the C are cylindrical?

Not sure your exact question here. The "C" indication on the later lenses meant coated elements as far as I know. The pre-C were not coated.

paul ron · Jan 12, 2016

sorry, i thought only the L series had floaters.

Xmas · Jan 12, 2016

Theo Sulphate said:
Here are some photos of the lens and the misaligned DOF index.

I'd ignore that the floating element is probably OK.

Xmas · Jan 12, 2016

paul ron said:
sorry, i thought only the L series had floaters.

The C 65 has a floater, the pre C did not.

The C lenses had multi coating the pre C single coating - I think.

MattKing · Jan 12, 2016

Xmas said:
I'd ignore that the floating element is probably OK.

But which mark will you use when you go to set it?

Theo Sulphate · Jan 12, 2016

MattKing said:
But which mark will you use when you go to set it?

Until it can be fixed, I'd use the aperture/shutter red dot because I'm assuming the only issue is the DOF ring being twisted right. So, in the photo you see, I've got the floating ring set so that infinity is aligned with the aperture/shutter dot.

The lens is nearly mint - so I can't imagine how this could've happened. Either it came from Mamiya this way (highly doubtful) or someone did some disassembly. That makes me wonder what else was done.

Also, I can't see any way of removing the front name plate - I wouldn't try it myself for fear of scratching the lens. I assume it would have to come off before the DOF ring could be realigned.

MattKing · Jan 12, 2016

I don't know whether this matters, but on my copy of this lens the name plate is rotated about 120 degrees from the location of yours.

And in my case, all three red indicators (depth of field centre, shutter speed and lens mount lock) align at the top, and that spot coincides with the limits of travel for the floating element distance scale.

Theo Sulphate · Jan 12, 2016

MattKing said:
I don't know whether this matters, but on my copy of this lens the name plate is rotated about 120 degrees from the location of yours.

And in my case, all three red indicators (depth of field centre, shutter speed and lens mount lock) align at the top, and that spot coincides with the limits of travel for the floating element distance scale.

Good to know, thanks. The limits of travel on my floating element ring seem to be correct as well.

Xmas · Jan 12, 2016

Theo Sulphate said:
Good to know, thanks. The limits of travel on my floating element ring seem to be correct as well.

You need a jar or pipe with an outside diameter of 76mm and a soft kitchen glove.
The name plate should unscrew easily...

But I'd not bother myself dab of nail lacquer...

flavio81 · Jan 12, 2016

Trail Images said:
Not sure your exact question here. The "C" indication on the later lenses meant coated elements as far as I know. The pre-C were not coated.

"C" means multi-coated in these lenses.

It's rare for a post-1950 lens to have no coatings at all.

flavio81 · Jan 12, 2016

Theo Sulphate said:
Until it can be fixed, I'd use the aperture/shutter red dot because I'm assuming the only issue is the DOF ring being twisted right. So, in the photo you see, I've got the floating ring set so that infinity is aligned with the aperture/shutter dot.

The lens is nearly mint - so I can't imagine how this could've happened. Either it came from Mamiya this way (highly doubtful) or someone did some disassembly. That makes me wonder what else was done.

Also, I can't see any way of removing the front name plate - I wouldn't try it myself for fear of scratching the lens. I assume it would have to come off before the DOF ring could be realigned.

It just unscrews by friction. You can try using your fingers. Pour a little bit of naptha on the filter threads if this is difficult.

Most likely the DOF ring can be adjusted after removing such front plate. Take a deep look.

BTW, the floating adjustment is not critical at all. That means, if you are shooting at infinity and the floating ring is set at, say, 8 meters, it's no problem at all.

John Koehrer · Jan 13, 2016

flavio81 said:
It just unscrews by friction. You can try using your fingers. Pour a little bit of naptha on the filter threads if this is difficult.

Most likely the DOF ring can be adjusted after removing such front plate. Take a deep look.

BTW, the floating adjustment is not critical at all. That means, if you are shooting at infinity and the floating ring is set at, say, 8 meters, it's no problem at all.

Except in the corners.
If you look closely while adjusting the floater you'll see the corners going slightly in and out of focus.

Theo Sulphate · Jan 16, 2016

Solved!

The DOF ring has been re-aligned!

A very experienced camera repairman I know fixed it in about two seconds - very embarrassing. So, there's no need to unscrew the nameplate: on this lens the DOF ring itself can be removed by simply twisting it with a bit of force. In my case, it just hadn't been twisted on fully. Earlier, I had tried twisting it but didn't do it forcefully enough since with camera equipment I tend to be gentle.

Anyway, everything now lines up and all is well.

DOF ring misaligned on RB67 65/4.5 C lens

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DOF ring misaligned on RB67 65/4.5 C lens

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