Canon 50mm/f1.8 CLA

[blee017]

I bought a black Canon 50/f1.8 with sticky aperture ring here on RFF from Scott. (Of course, Scott mentioned it and other than that the lens is in immaculate condition. Thanks, Scott!)
I happened to have another fungus-infested Canon 50/f1.8 and am trying to clean and lube it before I do any damage to the keeper.

I started on the back end of the lens first.
So far, I have unscrewed the rear spanner-slotted ring and all the screws I can see (ten of them) but for the life of me, I can't figure out how to gain full access to the focusing helicoid; the outer chrome ring wouldn't come off.
Any suggestions?

Thanks in advance.

 

[rover]

Brian is the man for this job. He should be awake in a couple hours.

 

[rover]

One more bump before I go make coffee and breakfast.

 

[back alley]

what time do you get up rover?

it's 6:30am here, i'm getting ready to meet up for breakfast with my saturday morning bunch.
joe

 

[Sonnar Brian]

> He should be awake in a couple hours.

And on a ton of Benedryl.

I have not broken this helical down, but those grooves in the first photo at 90degree angles look like the key. Before you tear into it, have you tried "flood cleaning" with Ronsonol or other solvent? I have had luck using such to free up and essentially adding some viscosity back into dried lubricants.

Otherwise, using my "best-dumb look" i'd be trying that slotted ring.

The module that gave me trouble on this lens was the last rear element that faces the aperture. The slots are inset. I shaped some fine needle nosed pliers to get it out.

 

[jlw]

It's too early for me to remember how the helical comes off (did you try unscrewing it through the front?) but, getting back to your original problem, I don't think you need to be doing this at all to address a sticky aperture ring.

Since this is a black (late-model) lens, the culprit is probably the notorious CYG (Canon Yellow Grease.) This stuff is used to lubricate Canon aperture rings and turns to adhesive over time. My 50/0.95 was sorely afflicted by it when I got it, but it proved pretty easy to clean off.

You get at the whole aperture mechanism through the front. The following is based on a 50/1.4, since I've done one of those a whole lot more recently than a 1.8, but take a look and see if it doesn't apply:

-- Take the optical section out of the focusing mount by removing the slotted ring around the rear element. Don't lose the spacer ring that determines the depth at which the optical section sets into the mount.

-- Split the optical section into its two halves by loosening the tiny setscrew in the side of the ring ahead of the aperture ring, and unscrewing the front half of the lens via the filter ring.

-- You've now got full access to the aperture mechanism. The aperture ring forms a 'cup' in which the front section sits. Remove the screw that couples the ring to the actual aperture mechanism, and a few other things that escape me at the moment but which should be obvious when you're looking at it, and you can take the ring off.

-- Clean off the smears of sticky yellow grease that you'll probably find inside the ring. Apply a very tiny amount of new, clean grease such as white lithium grease. Reassemble the ring, check for smooth operation, then put the lens back together the reverse of above.

As I said, I'm writing this without a 50/1.8 in front of me to disassemble and check these directions, so no guarantees! But I'd hate to have you go to the trouble of disassembling the focusing mount on your sticky lens when it's not necessary.

Now, back to the problem of getting the fungusy one apart... hmm, brain still no clearer, so will have to leave this one to somebody else...

 

[Sonnar Brian]

Are you also trying to relube the helical, or just repair the sticky aperture?

Just to mention, on my Canon 50mm F1.4 the aperture ring itself was the culprit. All those years of skin oil and dirt from being handled must have built up. Used a little isopropyl alchohol on it, freed it right up. No disassembly was required. This may not solve your problem, but it is easy to check out and probably should be done anyway.

 

[chendayuan]

to gain full access to the focusing helicoid
1. use a slot tip spener, unscrew the ring the hold the helicoid, it may stack difficult to unscrew
2. if you can not unscew it, drop some liquid wrench fluid
3. liquid wrench does not work then give up

This stupid design is the cause of famous canon lens wobble
whateven these Canon fans claimed. non of Canon lens can reach Leica's lens tighten tolerence and mechnical quiality, not even close. sorry Canon fans

 

[Sonnar Brian]

I have not experienced the Canon Lens Wobble. Any lens will wobble if a retaining ring is loose.I've tightened the retainging ring on my Nikkor 5cm f1.4. If it wobbles, it is a 1 minute fix. Most of the time required to get the lens off of the camera. Compared with my Leica lenses of the same vintage, the Canon coating is less prone to damage. It is easier to tighten a few retaining rings then to have a lens polished and recoated. But that never stopped me from buying Leica lenses.

 

[rover]

what time do you get up rover?

it's 6:30am here, i'm getting ready to meet up for breakfast with my saturday morning bunch.
joe

Now we are working here. I knew we could get this thing taken apart and repaired.

Joe, I went to bed at 7pm last night. I have been feeling relatively crappy this week, so I thought getting a little extra sleep would do me good. I of course was up at 4:45am this morning, but I can make that work.

 

[Sonnar Brian]

> I have been feeling relatively crappy this week

Your not the only one. Finally got the strength up to do a little yard work and clean the pool. Figured I'd use the hot tub to break up some congestion. I must have sounded pretty bad, I looked up and 10 Turkey Vultures were circling overhead.

I'm amazed I got the Lynx repaired yesterday. So easy, I could do it in a coma.

 

[back alley]

chendayuan , i can buy 4 canon lenses for the price of one leica and it's doubtful most people could tell which one took a pic. i'll stick with what i like.

rover, sorry to hear you have a bug. most of my illness this week entred around my car.
today the rad is leaking, can't win!

brian, my 100/3.5 is a bit wobbly...what do i do??
it unscrews and the part that is screws into is a tiny bit loose but i don't see anything to tighten.

thanks boys!

joe

 

[Sonnar Brian]

Joe, I do not have this lens. The screws are obvious on the 135mm F3.5 Late black lens.

While the turkey vultures were circling, I gave some thought to lens module inside the focus helical style of construction that Canon, Nikon, and Tanaka used in the '50s. Nikon and Tanaka had lines of lenses for S-Mount, Leica Thread mount, Contax mount, and even Exakta mount (for long lenses). The lens modules where identical between the lines; I can interchange the modules between the focus mounts of my Nikkor 135mm F3.5 across S-Mount, Contax, and Leica. I think it was a wise production move to minimize cost and sell lenses for multiple platforms.

So why did Canon do this? They only made lenses in Leica Thread Mount. I think they left themselves open to marketing lenses in S-Mount had Nikon been more successful. There are as many Canon 7's as there were Nikon Rangefinders, all models. But in the early 1950's, who was to say that the Leica Thread Mount would fall from grace and the Bayonet S-Mount compete with the patended and tightly controlled M-Mount.

Likewise with Nikon making a Contax Style bayonet mount camera based on the Leica standard. In the beginning, they sold more Leica Thread Mount lenses than S-Mount and it kept them alive. Had the S-Mount flopped, they could easily retool the Nikon S-Mount RF camera into a Leica Thread Mount camera by making a new front plate for it. The RF pickup was the same as what Leica used, the difference was that it rode the back of the built in helical. Take out the helical, make a new front plate with the 39mm thread mount, and you are in business. Nikon made two such prototypes.

What May not apear to be "as Elegent" may have been hedging bets. All designs are economic compromises. I work with optical engineers that love to throw out terms like "we'll make the whole thing in inconel" (a steel alloy with the same coefficient of thermal expansion as glass, ever seen a $40,000 lens?), or "it doesn't work like the models show, they only used a 5th order polynomial to approximate the aspheric surface" to which my answer was "were using a 320x200 CCD!"

I think that scared off the vultures.

 

[chendayuan]

Joe
Please do not tell me that Canon lens's coating is damage free. 50/1.2 is soft, no better than summicron, 50/1.8 the one elements behind the aperture is prone to coating damage, 50/1.4 can have have marks too, so does 50's nikon.

 

[blee017]

Thanks a lot for all the input, guys.
I am working on a geanie pig so I want to go as far as I can.
I gave up on dismatling the helical.
There are four slots on the brass ring but they are too narrow for the blade tip I got from micro-tools and the ring is screwed too tight for the pointed tip. (or it doens't come off that way.)
I dropped a bit of 3-in-1 oil and it turns more easily now.

Tackling the front end, I found that the element with fungi unscrews with the rear element from the housing.
Unfortunately, the glass has been etched, which will make me even bolder. 😀
There is a slotted ring on the rear element housing but somehow it doesn't turn.
It looks like it is cemented (pic 4). Hmm...

Now getting back to the problem I wanted to fix, sticky aperture ring, which screw(s) do I have to loosen (pic 1, 2, and 3)?
The ring is stuck wide open and there are several screws.

Thanks!

 

[Sonnar Brian]

That was me who told you that the lens coating in the Leica's were soft. That is fairly well known. I am talking about early to mid 1950's lenses, ie the time of the F1.2 and F1.8 Canon lenses. The Summarits and early Summicrons, those made in the same time-frame as the Canon lenses mentioned, had softer coatings. The Japanese lenses moved to hard coatings before Leica. After a few years, Leica caught up with them. You do not read about too many people having to get 1950's Japanese lenses recoated, but you do see Summarits and early Summicrons that require recoating. I have sent two Summarits, a Type I rigid Summicron, an M-Mount Hektor in for cleaning. I get the usual "We cannot guarantee that the coatings will not be damaged" speech. This does not happen with the Nikkor and Canon lenses of the same vintage. Leica improved their coatings as the 50's rolled on. By the time the first Summilux was out, the coatings had improved.

I wish someone had told Leica to use hard lens coatings earlier on. But I am not complaining about my $125 and $140 Summarits. I never would have gotten them at that price if the coatings didn't have cleaning marks in them. None of my nine 5cm F1.4 Nikkors, ranging from the first 1950 production batch to a late run SP show signs of cleaning marks or coating damage.

Here is a reference to the Leica FAQ maintained by Andrew Nemeth regarding the soft coating used on Leica's and the hard coatings used on their Japanese counterparts.

http://www.nemeng.com/leica/046b.shtml

 

[Sonnar Brian]

This is the same construction as the 135mm F3.5 that I took apart a year ago, so I'm a little hazy. I remember taking out the click stop mechanism in photo 1, being careful not to drop the greasy ball bearing, and taking off the fixture in picture 2 that calibrates actual F-Stop to that shown on the aperture ring. HAZY: I think backing off the set screws and the module unscrews. Where is JLW to confirm? Be careful of the set screws, I did this whole think in a cafeteria style lunch tray with white paper towels. Also used ice cube trays to I could lay out the parts in order of disassembly. Should have taken pictures...

 

[jlw]

Now getting back to the problem I wanted to fix, sticky aperture ring, which screw(s) do I have to loosen (pic 1, 2, and 3)?

You have to take off most of that stuff to get the ring off, but the real key is a flat brass circlip that's just barely visible in your photos. Once you've removed the screwed-on pieces (which mostly are for the clickstop mechanism) you need to remove this circlip so you can lift off the ring.

To make it a bit more clear, I just now ran into the other room and took a Canon 50/1.4 apart so you can see (how's THAT for service?) Sorry I couldn't do a 50/1.8 -- mine's currently off visiting another RFFer -- but I think you'll find the construction is very similar.

Click this link and see if it helps...

[Note: Once you're viewing the page, you can click any photo to see a larger version.]

 

[chendayuan]

Sorry Joe, I hit the wrong target. material wise, Canon 50/1.4 is lousy compare to Summarit. the focusing helical was fixed by the retain ring, you have to have some play to alieve the helical to move, if it lose or wear wobble will show up. in my opinon, very economic and poor design. all my Canon 50mms have some degrees wobble or play. I have see clean mark Nikon 50mm but not as bad as summarit.

 

[jlw]

Material wise, Canon 50/1.4 is lousy compare to Summarit. the focusing helical was fixed by the retain ring, you have to have some play to alieve the helical to move, if it lose or wear wobble will show up. in my opinon, very economic and poor design. all my Canon 50mms have some degrees wobble or play.

The retaining ring holds the optical section INTO the helical. The helical is rigidly attached to the mount thread via screws. Play is NOT necessary for this design to function properly. All the materials used are of high quality -- all-brass helical, for example -- and are beautifully finished.

If the retaining ring works loose, the optical section will wobble IN the helical, and if the screws work loose, the helical will be loose on the mount thread. But both those symptoms appear only with long wear, and both are alleviated easily by tightening. (And as Joe says, ANY lens -- including those from makers whose names begin with "L" -- can get wobbly if their screws and threaded rings loosen up.)

One Canon quirk that DOES seem to have something to do with design is a radial slackness that sometimes appears in the focusing ring. It's most common with the 50/1.4, but I've also seen it in the 50/1.8. You feel this slackness when you twist the focusing ring: There's a slight initial free movement before the helical begins to drive the lens.

I believe this is caused by wear in the focusing guide tab, which moves in a slot cut into the focusing helical. The job of this guide tab is to force the lens to move forward and backward, rather than just twisting, when you twist the focus ring. Over time it seems that enough clearance opens up in the slot that the tab has some slight sideways free movement before it resists. I have speculated that a repair technician could cure this by splittiing the tab and inserting a small screw to widen it slightly, but I've never felt it was worth trying. Note that this play is NOT in the helical itself, and does NOT have any effect on focusing accuracy or lens-to-film alignment. It's simply a slightly annoying feeling as you focus the lens.

Maybe the Summarit is better in terms of material choice and construction, but you couldn't prove it by the example I used to own! The wall of the focusing ring tube was so thin that if you gripped it firmly while turning it, it would distort into an egg shape and you could feel it dragging against the inner barrel! I suspect Leitz was trying to save weight by making this ring so thin, but it certainly didn't do anything for the "quality feel" of the lens.


[PS -- Mechanical considerations aside, in terms of optical performance the Canon is vastly better than the Summarit...]