Contax S2 shutter adjustment

I was reminded recently of a post I made, some years ago, on Rangefinder Forum describing the adjustment of the Nikon FM2 shutter (later used in the S2). I thought posting it here might be a good idea. It's been edited from the original to remove the Nikon references and change a few specifics based on more recent experience.

Note: Some of the pictures are of other, similar, shutters so may not be exactly as the S2 shutter but they serve to show specific features.

The S2 shutter is a mechanical shutter with speeds from 1 sec. to 1/4000 sec. plus B. The shutter was made by Copal and is a variant of the Copal square shutter.

The shutter curtains are timed by a cam rotating around a shaft driven by a spring. The spring has a small amount of adjustment to its tension. The position of the cam at which the second curtain is released is fixed but the position at which the first curtain is released is moved when changing speeds. This is the only method used to adjust between the top four speeds (1/500 - 1/4000 sec.). slower speeds use an escapement and a number of linkages to hinder the rotation of the cam and so decrease the shutter speed. The two curtains are driven by individual springs each with its own tensioner. Once the curtains are released, they travel independently and have no interaction.

As mentioned, the main spring has some adjustment which will cause the main shaft to rotate more or less quickly. This affects all shutter speeds but the affect is mostly to the slow speeds with minimal affect to the high speeds.

There is an adjustment that alters the timing between the release of the first and second curtains. This affects the high speeds with no affect to the slow speeds.

The curtain tensions can also be altered to increase or decrease the travel time but this isn't recommended.

Adjustments can be made with the shutter in-situ but the high speed adjustment is easier with the shutter removed from the camera. Note that the mirror box of the camera needs to be removed to access the high speed adjustment. 

Image 1 shows the main operating levers that cock and trip the shutter.

Image 2 shows the location of the adjustments.

Image 3 shows the location of the curtain springs and the slow speed escapement.

Check all the speeds before making any adjustments. Only adjust what is necessary which is usually just the high speeds.

If you need to, adjust the slow speeds first then the high speeds. Note that this is a mechanical shutter and the speeds will not be perfect. It's quite typical for the top speed to be a little slow. All the speeds should be checked after each adjustment and some compromise may be necessary to get all speeds to within acceptable limits. Note that the 1/250th always runs slow to ensure flash synchronisation is acquired.

The main shaft has a disk attached to the top with a number of slots in it. The end of the main spring sits in one of these slots. See image 4. To adjust the slow speeds, move the end of the main spring to a different slot to either increase or decrease the tension as required. I've found the fingers forming the slots get pinched together by the factory to stop the spring end from slipping out so the fingers need straightening first to allow the spring to be moved. A flat bladed screwdriver pushed between the fingers usually does it. BEFORE moving the spring, wedge the tip of a screwdriver behind the spring end so that, if it slips out of the slot or you lose your grip on it, it won't fully unwind.

Note: The disk on the top of the main shaft that has the slots in it has a slotted hole that fits over a matching raised part on the end of the shaft. In theory, it would be possible to remove the disk and refit it turned by 180 degrees. See image 5. This would allow the spring to be tensioned an extra half-turn. I've never had to do that but if a spring was particularly weak, it might be a solution. The screw holding the disk in place is left hand threaded so turn clockwise to unscrew.

To adjust the high speeds, identify the high speed adjuster. See image below. It looks like the head of a screw with a slot in it but it's only visible side-on and the slot may not be facing you so may not be visible. Because it's not possible to engage a screwdriver in the slot in the normal way, it's necessary to use the tip of a flat bladed screwdriver pushed sideways into the slot to turn it.

If the slot isn't facing you then you need a screwdriver with the tip bent 90 degrees to get into the slot.  Note that, usually, only a very small movement is required.

Just to reiterate, check all the high speeds after adjusting the high speed adjuster and check all the slow speeds after adjusting the main spring as a compromise may need to be made. The below image shows the typical speeds after adjustment. I fire the shutter multiple times at each speed and plot the highest and lowest values to check for consistency. This was a good shutter - you may not get the speeds this close to ideal. But they should be within the upper and lower limits (red and green lines). Note that 1/250th (flash sync speed) has it's tolerance all on the over-exposure side because, if it runs high (under-exposure) then cut-off may happen when using flash.

My S2 - it's a keeper

 I bought this S2 a while ago - someone had squirted oil into the shutter and had removed and refitted the focus screen incorrectly which caused other problems. I couldn't save the shutter so it was replaced and various other repairs carried out. The interesting thing (to me anyway) is this example has been converted to have average metering like the S2b instead of spot metering. The mask that defines the spot area has been swapped for the mask that is normally in the S2b. Maybe the masks were swapped between a S2b and this S2 or maybe it was done when spare parts were still available and someone acquired and fitted the S2b mask. However it was done, it suits me as I've never liked the spot metering. So I think this one's a keeper.

The covers I've fitted are some fabric covers I'm experimenting with. Also available in blue and black if anyone is interested.

Canon EOS EF Eyecup will fit Contax and Yashica

The Kyocera F-3 eyecup was used on the Contax S2, 167, Aria and maybe other bodies. It also fits earlier bodies like the 139, 137 and 159 and also Yashica bodies like the FX-3, FX-D, FX-103 etc. I, personally, prefer it to the round eyecups that were used on the earlier Contax and Yashicas.

However, the Kyocera F-3 eyecup has become scarce and when they do become available they are expensive. So I looked for an alternative and found the Canon EOS EF eyecup fits perfectly. It's the same style as the Kyocera F-3 though slightly different in shape. Original Canon eyecups are available and are not expensive but there are Chinese made copies that are available very cheaply on ebay.

The Canon EF eyecup fits Canon EOS 350D, 400D, 450D, 500D, 550D, 600D, 1000D etc. bodies. There are other similar models so, if buying, check it's the correct one.

Here's a few pics of one I bought fitted to a FX-3, a 139 and the KF-M1 mentioned in my previous post.

And a couple of pictures of the eyecup itself.

Yashica FX-3 Super 4000 anyone?

 I recently acquired a Map KF-M1 camera. Made by Phenix in China using a Yashica FX-3 chassis, it has a Nikon lens mount and a top shutter speed of 1/4000 sec. It's the same camera as the Kenko KF-2N which was clearly an attempt to create a camera with the same specification as the Nikon FM-2n. The Map version was made exclusively for Map Camera in Japan and, unusually, has no branding on it. There was another version called the Phenix DN66 sold in the Chinese domestic market.

I was intrigued how the top shutter speed was achieved. The Nikon FM-2n uses the same Copal shutter as the Contax S2 and I knew that shutter will not physically fit into a Yashica FX-3 chassis - I've tried it. The shutter is larger and has slightly different mounting positions. So, to find out how it was done, I had to get a camera. All the variants are rare and, if you do find one, expensive. But I found a KF-M1 in China. The seller accepted an offer but it still cost me nearly £190 with the import tax paid.

With the camera dismantled, first inspection of the shutter suggested it was the same shutter as is fitted to the Yashica Super 2000 (and many other cameras) but it has an extra position on the shutter speed selector. A check of the shutter speeds shows it is struggling to get to 1/4000 and the general shape of the test results graph is very similar to that from a Yashica Super 2000.

(Note: The upper and lower limits on the above results sheet are from a Contax S2 and are not correct for the KF-M1. They should be the same as the FX-3 limits below.)

It's not unusual for the Yashica Super 2000 shutter to be slow at the top speed but some adjustment will usually bring it into specification. I'll have to see if I can get the KF-M1 shutter closer to what it should be.

So it appears Copal produced a further upgrade to the 2000 shutter, which was itself an upgrade of the original 1000 shutter as used in the original FX-3. So I'm surprised that a Yashica Super 4000 never appeared if the shutter was available and could be fitted with no modification to the existing FX-3 chassis. Maybe it was because it would be competing with the Contax S2.

Now I need to decide what to do with the dismantled KF-M1. I don't want a camera with a Nikon lens mount. I could fit the shutter into an existing FX-3 Super 2000 or I could fit a Yashica lens mount to the KF-M1. The camera is quite well made and, unlike the Yashica with plastic top and bottom plates, the KF-M1 has metal top and bottom. The focus screen is the original Yashica one with the diagonal split prism, which I don't like, but if I change the lens mount I'll also have to change the viewfinder so that's not an issue. Whatever I do, the camera is unlikely to get a lot of use from me so if someone out there has an urge to own a Yashica Super 4000, get in touch and we can discuss.

Update: There is now a part 2 to this post at https://contax139.blogspot.com/2021/02/yashica-fx-3-super-4000-part-ii.html

Focus screens

As I mentioned in the previous post, the S2 screen needed replacing because it was scratched. Replacement S2 screens can be found but are usually expensive. I did buy a used one from a well known UK dealer but, when I got it, it was also scratched so it went back. They can be found on ebay, usually from Far East sellers, but can be anything up to £60 or more.

The same screen type is used in the Contax 167 and the Aria so finding a broken 167 or Aria might get you a good screen but the cost is likely to be no better.

I investigated a number of other screen types to see if they would fit and, believe it or not, the 139 screen is perfect. Because the 139 screen isn't user replaceable, there's no tab on it so fitting it is a bit more difficult but the size is the same.

One good thing about the S2 is the screen is aligned by its top surface which is the surface which the image is formed on so any slight differences in screen thickness won't affect the focus. Other cameras align the screen using the bottom surface so the thickness has to be correct to get the top surface at the correct distance from the lens.

So if anyone want's a replacement S2 screen, a 139 screen may be the cheapest answer.

S2 fixed

Finally got the S2 shutter sorted and the camera rebuilt. Besides the shutter issues, the mirror had slipped and required removing and refitting, the focus screen was scratched and needed replacing, someone had glued an eyepiece to the camera that had to be removed and the glue cleaned off, the meter was dead and the seals needed replacing. All now done so I just need to load a film and start using it.

S2 Problems

I bought an S2 a few weeks ago from a dealer in Japan who described it as good condition but with a faulty meter. The fault meant it was a fair, though not necessarily cheap, price. I bought it with the view of fixing it and keeping it. On receipt, though, it was obvious there were several other problems with it. A few emails back and forth and the seller agreed my, much reduced, valuation of the camera and gave me a partial refund.

One of the problems was massively slow top shutter speeds. To do anything with the shutter usually means removing it and that means an almost total dismantle of the camera. Here's the camera now.

The shutter (top middle) is not intended to be repaired or adjusted. The manual says shutters come pre-adjusted and gives no information on how to adjust them. I've worked on these shutters before and have discovered the general principles of how to adjust them but the process is more art than science and this one is not cooperating. I might have to find a replacement.

Here's the shutter back in the camera for testing after one of my many attempts to get all the speeds to within specification.

I'll post further news of this adventure in camera repair as it happens.