Normalness of Rokkor-NL 21mm looseness

[dwainasaurus]

I've been using a MC W.Rokkor-NL 21mm for a little while. The front end of the lens seems to be loose. I've always assumed this is normal but would like to know for sure. The front end, the metal in front of the focus ring, seems only to act as a hood and non rotating filter holder. Are there any other users of this lens that can verify this looseness is correct?

I've posted a couple images of the W.Rokkor-NL 21mm on my blog to help make sure we are all talking about the same version of the 21mm 2.8. (I think mine is an early version).

[scsambrook]

If this is a rotational movement, my guess is that it's built up over the years from previous owner(s) gripping on the front ring to mount and remove the lens. From memory of handling various Minolta lenses in the past, this sort of movement isn't uncommon, and if it's only about a millimeter as your blog says, then I doubt if it will spoil the performance at all.

[dwainasaurus]

Thanks for the reply, Stephen.

The looseness is in every direction. The hood (for lack of a better term) moves front to back, up and down, and a slight rotation also. All movements are less than one millimeter.

I'm glad to hear that this is normal for some Rokkor lenses.

BTW, it seems like the front element is not directly attached to the hood. When I make the hood move the front element does not move. Also, while focusing, the front element rotates but the hood does not. The hood movement, the non rotating of the hood while focusing, and the rotation of the front element all seems so counter intuitive.

[scsambrook]

It's a long, long time since I saw one of these and I just can't remember the details of what moves and what stays put. But if the optical section is free of movement then I reckon you're okay - if you mount and remove it by holding the rear of the lens body (which I think is what we're SUPPOSED to do!) then it will probably stay in its present condition for the next century.

Love to see some pics taken with it!

[peterqd]

Dwaine, I don't know this lens and the rotating front element is new on me. But, I had a similar problem with the CZJ 2.8/20 so this might help.

I don't think the filter ring should be as loose as this and I agree with Stephen that it has probably worked loose through gripping it. I would expect that the ring is either fixed to the barrel with three screws or possibly clamped with a large diameter screwed ring which simply need tightening.

First you need to remove the engraved front bezel ring using a friction tool and this should expose the fixing method. The large front element might make access difficult and you'll need to decide if you want to unscrew the front lens block. Normally this is straingtforward in my experience. If there is a clamping ring you might need a lens spanner with blade ends. Removing the bezel is easy - if you want, why don't you do that and take a pic for us.

[dwainasaurus]

Update:

I mustered up the courage to pick up a tiny screw driver and take a closer look. My first step was to loosen and then re-tighten the 'hood' screws. The second image on my dwainasaurus blog shows the screws I loosened. Not the shiny one on the focus ring but the ones right in front of the focus ring. This tightening did not resolve the looseness. Next I removed the screws to remove the entire 'hood'. I call it a hood but I am talking about the entire barrel forward of the focus ring.

What I found was both good and bad. (I think).

The good: The 'hood' is attached with three screws to a ring at the base of the focus mechanism and doesn't touch any other part of the lens. The front element is completely separate from the 'hood' so the looseness in the hood cannot affect the image path.

The bad: The 'hood' attachment ring is obviously a tiny bit wobbly. But it isn't clear to me how that ring is attached because it is mostly covered by the focus ring.

At this point I chickened out and reassembled. I am not a camera technician and figured it would be too easy to do more harm than good.

This 'hood' style of assembly seems like a pretty odd way to build a lens. Any idea what Minolta was thinking?

[guatipen]

hi..
i'm Andres from spain...

i have the 21mm and is an amazing lens...

there is two version of the lens, both the same optic quality, but a little differences :

ones from 1971, the older is the lens you have... has an MC-II style, with the aperture crhme ring and the Focus grip became shorter and got more embossed concave knurled sections...

the later 1972 with Rubber focussing grip and black aperture ring.

The Minolta MC W. Rokkor 21mm f2.8 was one of the best ultra wide angle lens made by Minolta and was the first to use a complex "floating elements design"

from http://www.sds.com/mug/mf-lenses.html

" An improvement in lens design, called the floating focusing system, changes the spacing between lens elements as they move along the focusing helicoid. In other words, the lens elements do not move in unison. Some appear to "float" in relation to the others. This reduces aberrations at close focusing distances with short-focal-length lenses.


kind regards...

[walter g]

guatipen
Thank you, for the link. That has the lens info that I have been looking for.
This fils in alot of what's not on the Rokkorfiles site.

Thanks again, Walter

[peterqd]

Yes, thanks from me too. I was interested in the part about using MC lenses in P mode. On my XD-7 the aperture LEDs don't show in P mode unless the little lever is actuated by the aperture ring. The only difference I can see between MC & MD lenses is the lug that moves this lever so I was planning to try adding a lug to one of my MCs to test the theory. Now I know it will work!

[dwainasaurus]

Update #2

Thanks to everyone who chimed in with information and links to information.

I've decided that the tiny bit of movement is normal for a used lens of this design, doesn't affect the image path, and I should stop worrying about it.

I don't have an efficient means of getting my images digitized yet. So I scanned one print. Pretty significant quality loss during scanning. I have also posted a full size version of this same image in the Minolta X-370 review. Hopefully by the time I finish the review of this 21mm I'll have more images digitized.

[dwainasaurus]

The poor quality sample image above has been replaced. To better represent what the gear is capable of producing a Minolta Dimage Scanner was used to scan the negatives. Updated images are now posted at the bottom of the page in the X-370 review. Use caution when viewing the full size image. It is a 9 mb .jpg file.

[wj cody]

hi, i'm new to the forum, so forgive me if all this is old news.
i have 2 of the 21mm 2.8 minolta nl rokkor lenses.
one has the loose front end. i'm currently having Erv Hill dismantle it and see if it can be put right. my 2nd lens is a rokkor x and a bit newer. i'll let folks know what Erv finds out and what's needed to make a repair.
kindest regards to all,
cody

[Lightshow]

My MCII version is not loose, and thanks for the link.

[hifisapi]

If it doesnt affect optical quality and its an expensive repair, I would just leave it be.
But I understand how its annoying. I hate little things like that in a lens.