peterlove

Thank you for the reply, I am using a Mamiya RB67 pro SD and my metering is by handheld meter, I also use the Cokin filter system I already have a circular polariser and I have just found a linear polariser on ebay, so, I will be making some comparisons.

Thanks again. Peter.

Hi all I understand that it is not ok to use an analogue polariser on a digital camera but is it ok to use a circular polariser on film ?.

Peter.

I use P size filters on my RB67 and 50mm lens and they don't vignette, just. The filter holder I use is the Cokin P size and it attaches with the 77mm adapter ring.

 

If I forget to remove the 77mm protective Skylight filter from the Mamiya 50mm lens and attach the Cokin filter holder to the Skylight rather than the lens directly then the P filters vignette. That's how close tolerances are.

That's great to see this post I also have a Cokin P set of filters and holder I will be using them on a 65mm lens on my RB67 pro SD I have also hacksawed the two front slots off of the holder, so, going on what you say in your post I should be more than safe from vignetting when I photograph the sunrise on the longest day 2022. Regards Peter.

Ben, thank you for taking the trouble to look into the loose 90mm lens problem, all your observations and checks noted, my camera is the Pro SD version and all of my associated lenses and any other accessories are for that model, all lenses are K/L type, I have had my suspicions about the 90mm lens ever since I acquired the RB67 a couple of years ago, I noted that the chrome collar nut that secures the X terminal had a damage mark revealing the brass where a tool had slipped during tightening, I have now looked more closely and found that the large collar nut down passed the rear lens had marks also, on checking this I found it had not been tightened securely, the lens now has less movement than before, however, I am not entirely happy that whoever opened the lens had the skills to make a good job, I have used the lens in the passed and the resulting pictures look ok to me, however, I think I will be looking for a replacement lens, I have my eye on a 65mm K/L if I buy that it will be an addition to my collection and I can make some comparisons.

Once again Ben thanks for your reply and help.

Peter.

Alright, I'm going to jump and say based on some quick testing that the ring probably IS your problem.

 

My 90mm K/L is usually on my Pro SD and it's rock solid. When I pulled the spacer ring off, it's fairly floppy around the mount.

 

I also tried the same with my 127mm pre-C. With no ring, it flops all over the place. With the ring installed, it's not as tight as the 90mm or my other K/L lenses, but still has very, very little slop.

 

Both lenses are good on my Pro-S without the ring installed. The 90mm has no perceptible looseness, while the 127mm is very slight-about the same as on a Pro-SD body with the ring.

 

The rings are often stated to be for stopping light leaks around the lens, but based on your question and my quick experiments, it seems that it's also for mechanical tightness.

 

I've seen rings on Ebay, but to me the price is a bit steep at $30-40 each. I think I might have paid $125 or so for my 90mm with both caps and the ring included(KEH bargain grade).

 

At the moment, I have 4 lenses for my RBs-two K/Ls, one C, and one Pre-C(that reminds me that I need to go grab the 150mm SF that the camera store is holding for me). I also have both a Pro-S and Pro-SD body. This means that I need to keep the rings in mind depending on the body I'm using. I suspect they wouldn't be that difficult to machine(a piece of nylon would probably work every bit as well as the metal/rubber ones) but I also suspect that a heavy O-ring of the correct size would provide much the same function. That's something I need to try-$5 for 100 O-rings from McMaster Carr seems a much better deal than $30 for the official Mamiya piece :)

Hello, this is my first shot at posting on this forum, I have an RB67 Pro SD and three lenses, 90mm, 127mm and 180mm, ( all K/L type) the 127mm and 180mm fit snug and perfect when the collar is tightened, the 90mm after tightening the collar is not pulling down tight even though the collar is turned to its stop, visually I can see no mechanical reason for this, I should add that I am a retired Volkswagen technician and I well understand things mechanical.

Peter