Home

Please support mflenses.com if you need any graphic related work order it from us, click on above banner to order!

SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Interesting Sekor zoom
View previous topic :: View next topic  


PostPosted: Fri Oct 28, 2016 8:14 pm    Post subject: Interesting Sekor zoom Reply with quote

I acquired this odd Mamiya Sekor CS zoom, never heard of it before.

Apparently this lens is hard to find and has a deadly flaw. A rubber part inside degrade to black sticky goo and get deposited on the lens elements.
I think it's another user from here that has made a guide how to clean it.

My copy has survived in a good condition, the offending part is there but not on the glass.
It would be nice to clean it and put it to use.





PostPosted: Fri Oct 28, 2016 8:48 pm    Post subject: Reply with quote

Certainly a rare beast, obvioulsy because of its "self-destructive" rubber inside part (probably a rubber shade):
http://artaphot.ch/mamiya-cs/mamiya-cs-objektive/429-mamiya-cs-45-90mm-f35
http://mamiya-nc-m42.mflenses.com/cs_45-90_3.5.htm

All Mamiya CS lenses:
http://mamiya-nc-m42.mflenses.com/cs_lenses.htm


I bought my sample in 2015 and, after searching the net without success, decided to clean it anyway. It's not really difficult, you just have to start from the front side. Don't touch the zoom mechanism and its calibration!!

See here on my website for details:
http://artaphot.ch/mamiya-cs/mamiya-cs-objektive/433-mamiya-cs-45-90mm-f35-repair

Stephan


PostPosted: Sat Oct 29, 2016 1:15 pm    Post subject: Reply with quote

That's quite a big lineup of CS lenses!

Your cleaning guide will be very helpful, if I dare to open it. It doesn't look like spanner required, I'll have to translate.


PostPosted: Sat Oct 29, 2016 7:45 pm    Post subject: Reply with quote

blotafton wrote:
That's quite a big lineup of CS lenses!

Your cleaning guide will be very helpful, if I dare to open it. It doesn't look like spanner required, I'll have to translate.


No, i just have been using small screw-drivers. A machine translation probably gives only nonsense; i might try to do a rough translation myself, on Monday ...


PostPosted: Sun Oct 30, 2016 10:46 am    Post subject: Reply with quote

Looks like I can do it!

Google translate is quite good:
https://translate.google.se/translate?sl=de&tl=en&js=y&prev=_t&hl=sv&ie=UTF-8&u=http%3A%2F%2Fartaphot.ch%2Fmamiya-cs%2Fmamiya-cs-objektive%2F433-mamiya-cs-45-90mm-f35-repair&edit-text=&act=url

The only things I don't understand is how to remove and replace the rubber focus grip. And also this last part:

Alles in allem erwies sich die Reinigung als weniger aufwändig als zunächst befürchtet. Dies ist v. a. der klaren Konstruktion des Mamiya-Zooms zu verdanken (wesentlich übersichtlicher als andere Viergruppenzooms zB von Minolta). Da für die hier geschilderte Reinigung einzig die Frontgruppe abgenommen werden musste, blieb die Justierung von Grundobjektiv / Variator / Kompensator erhalten. Das Grundobjektiv lässt sich übrigens noch einfacher als die Frontgruppe entfernen: Unter dem Gummi des Zoomringes liegen erstens drei Schrauben, die man NICHT anrühren sollte. Im Zoomring sind aber zweitens drei weitere "Löcher" sichtbar, in denen (falls der Zoomring in die richtige Stellung gedreht wurde) weitere drei Schrauben sichtbar werden. Werden diese gelöst, so lässt sich das Grundobjektiv zwanglos herausnehmen. Zurück bleibt die eigentliche Zoomgruppe mit Variator und Kompensator.

Any advice on black paint or other product to reduce reflections?


PostPosted: Mon Oct 31, 2016 11:53 am    Post subject: Reply with quote

Quote:
The only things I don't understand is how to remove and replace the rubber focus grip. And also this last part:


Alles in allem erwies sich die Reinigung als weniger aufwändig als zunächst befürchtet.
Cleaning of the lens was less problematic/difficult than expected,

Dies ist v. a. der klaren Konstruktion des Mamiya-Zooms zu verdanken (wesentlich übersichtlicher als andere Viergruppenzooms zB von Minolta).
mainly due to the well-thought-out construction of the Mamiya zoom (much clearer than other four group zooms eg from Minolta)

Da für die hier geschilderte Reinigung einzig die Frontgruppe abgenommen werden musste, blieb die Justierung von Grundobjektiv / Variator / Kompensator erhalten.
Since for cleaning only the front group had to be dismantled / removed, the adjustment of main lens / variator / compensator was retained

Das Grundobjektiv lässt sich übrigens noch einfacher als die Frontgruppe entfernen:
The main lens can be removed even easier than the front (focusing) group:

Unter dem Gummi des Zoomringes liegen erstens drei Schrauben, die man NICHT anrühren sollte. Im Zoomring sind aber zweitens drei weitere "Löcher" sichtbar, in denen (falls der Zoomring in die richtige Stellung gedreht wurde) weitere drei Schrauben sichtbar werden.
Under the rubber of the zoom ring there are three srews which should NOT be touched. looking at the zoom ring (rubber removed!) there are three more holes visible. Within these holes one can see three more screws, IF the zoom rings is turned to the right position.

Werden diese gelöst, so lässt sich das Grundobjektiv zwanglos herausnehmen. Zurück bleibt die eigentliche Zoomgruppe mit Variator und Kompensator.
If these three srews are loosened, the main lens comes out without any difficulty. What remains, is the zoom group (variator & compensator).

Quote:
Any advice on black paint or other product to reduce reflections?

I've been using a simple black spray to paingt the bright silver parts. Of course that will be less efficient than the original (now dissolved) bellows, but that's the best solution i found ...

Stephan


PostPosted: Mon Oct 31, 2016 4:02 pm    Post subject: Reply with quote

Thank you!


PostPosted: Tue Nov 29, 2016 4:21 pm    Post subject: Reply with quote

Did you succeed in cleaning your rare Mamiya CS 3.5/45-90mm zoom?

Stephan


PostPosted: Wed Nov 30, 2016 11:15 pm    Post subject: Reply with quote

Did you use the lens?

Did you take pictures with it?


PostPosted: Thu Dec 01, 2016 4:45 pm    Post subject: Reply with quote

papasito wrote:
Did you use the lens?

Did you take pictures with it?


Not really, since i don't have an Mamiya E/CS => Sony E adapter. I did a few "improvised" shoots simply pressing the lens to another adapter (i don't recall which one). This works fairly well with primes (at least as long as they have no floating elements), but with zoom lenses the correct distance between master lens and sensor is important. Therefore the results i got are certainly not representing properly the Sekor 45-90mm ...

Stephan


PostPosted: Fri Dec 02, 2016 5:45 am    Post subject: Reply with quote

I wonder how it compares to the Yashica ML 42-75, the ML looks like it's half the size, then again it's f3.5-4.5.


PostPosted: Fri Dec 02, 2016 12:42 pm    Post subject: Reply with quote

stevemark wrote:
Did you succeed in cleaning your rare Mamiya CS 3.5/45-90mm zoom?

Stephan


Not yet. I'm still not sure how to remove the rubber grip in a non destructive manner. Or if I should just cut it open and then try to glue it back afterwards.

If it works I'll buy one of those 3d printed adapters and take some shots!

Lightshow wrote:
I wonder how it compares to the Yashica ML 42-75, the ML looks like it's half the size, then again it's f3.5-4.5.

I have that lens, could be an interesting comparison since the 42-75 preforms quite well.


PostPosted: Sat Dec 03, 2016 12:35 pm    Post subject: Reply with quote

Quote:
I'm still not sure how to remove the rubber grip in a non destructive manner. Or if I should just cut it open and then try to glue it back afterwards.


I'm still looking for advice on this. The guide on stevemark's website does not show how. I am a novice in lens repairing.


PostPosted: Sat Dec 03, 2016 1:36 pm    Post subject: Reply with quote

blotafton wrote:
Quote:
I'm still not sure how to remove the rubber grip in a non destructive manner. Or if I should just cut it open and then try to glue it back afterwards.


I'm still looking for advice on this. The guide on stevemark's website does not show how. I am a novice in lens repairing.

Oh, that's quite easy.

1) carefully try to push a small (!) screwdriver about 2-3mm under the rubber. I guess from the back end it's easier. Then carefully pull a part of the rubber over the metal part that usually is keeping the rubber in its place. Do the same thing 1-2 cm further away, and continue like that until you have pulled the entire rubber ring a few millimeters over the (larger) metal part mentioned above. Once you have completed this, you can push/pull the entire rubber ring backwards ... Simply try not to over-stretch it during the procedure. Sometimes, if the rubber is a bit tight and not gliding well over the metal, you may add a small amount of oil between rubber an metal.

No problem at all, and certainly no need to cut the rubber!!

Stephan


PostPosted: Sat Dec 03, 2016 4:32 pm    Post subject: Reply with quote

Thank you so much! Now I can start!


PostPosted: Mon Dec 12, 2016 5:21 pm    Post subject: Reply with quote

If you manage to take a few images (better than mine) of your repair attempt, we might put them on the artaphot site (of ourse under your name). Others might find them helpful ...

Stephan


PostPosted: Mon Dec 12, 2016 5:50 pm    Post subject: Reply with quote

stevemark wrote:
If you manage to take a few images (better than mine) of your repair attempt, we might put them on the artaphot site (of ourse under your name). Others might find them helpful ...

Stephan


Yeah sure! Smile


PostPosted: Mon Dec 12, 2016 8:22 pm    Post subject: Reply with quote

Progress so far. I got the grip off focusing ring by following your advice. It was a bit tricky but it worked!



PostPosted: Fri Dec 16, 2016 1:18 am    Post subject: Reply with quote

So I cleaned it out. Not very difficult but really tedious, took the whole evening.

If anyone else wants to makes this repair my only recommendations are to have a good set of small screw drivers and some experience using them. Tiny screws like this are easy to damage.

To replace former rubber part I conveniently found a hair tie and just stuck it on there. Probably not the best solution but it'll likely block reflections just fine.

A big thanks to stevemark for the excellent guide! If you like these photos you can use them on your website.



Messy!




All that was on the actual glass.









PostPosted: Fri Dec 16, 2016 3:51 pm    Post subject: Reply with quote

The last image is the best!! Wink

Thanks for sharing!

Stephan