Arco Colinar f13.5cm/3.8 LTM

[BJ Bignell]

Just some notes and some pictures from the disassembly/reassembly of my Colinar 13.5cm lens. I bought this lens off of eBay for $9, and I got what I paid for. It had bad haze on the second element, a big dent in the filter ring, and was so stiff it would twist off of the camera when I tried to focus. So much for trusting in the word "clean"! 🙄

This is going to take me a while to get this all out, so I'm going to post bits and pieces as I can, and if I don't finish tonight, be patient... it's coming.

First, some general notes about the lens:

• Arco Colinar 13.5cm lens, maximum aperture of 3.8
• Continuous aperture settings (no click-stops)
• Aluminum body with brass and metal underneath. A heavy lens, but relatively compact.
• Stands about 10.8cm tall when focussed at infinity, 12.4cm tall when focussed at closest setting. Close focus of just short of 5'.
• Four elements in three groups, unit focussing. Probably inspired by the Leitz Hektor or Elmar lenses.
• On my version, the front element does not appear to be coated. The remaining elements are coated. There is a "C" version (big letter on the name ring) that is probably fully coated, or has an improved coating.

Now, some repair tips:

• With grub screws, only turn them out enough to remove the piece they are holding. After the piece has been removed, screw the grubs back in a bit so you don't lose them.
• The rear side of the front element is very, very soft glass. Don't ask... 😡
• This lens can only be correctly assembled in one way; don't worry about marking it, or trying to keep track of what was where.

Here's a picture of the lens.



And here are pictures of the front elements, highlighting the clear spot that was in the middle of the haze. The haze was on the front of the second element. The clear spot turned out to be free from haze, and from coating! This lens may have had fungus at one time, or been poorly coated in the factory, causing this defect.

 

[BJ Bignell]

The front elements can be easily removed by unscrewing them from the rest of the lens barrel. Firmly grasp the lens (covering both the focus ring and aperture ring) in one hand, and twist off the top part.


To access the front of the second group, and the rear of the front element, again unscrew these parts. Grip the smooth black section of the lens, and twist off the aluminum part from the top.


When you're not working on these lenses, it's advisable to screw them back together and set them aside, so that they are less likey to roll off the table, or to get banged around.

To clean the haze on the front of the second group, I used a 50/50 mix of vinegar and hydrogen peroxide. At first, I applied the mixture gently with a q-tip, and let it sit before wiping. This had no effect. I found I had to scrub, and fairly hard, to get the haze off. The coating was very strong, and didn't seem affected; there were no scratches evident when I was finished.

As mentioned before, the clear spot near the center of the lens initally appeared to be clear from haze, but it's also clear from coatings. When I get my test shots back, I'll see how much of a difference it makes.

 

[BJ Bignell]

The front element can be removed from the aluminum ring by unscrewing the retainer ring at the rear with a spanner wrench (see picture). Be careful, as this glass is very soft, and I scratched mine while gently cleaning it with a lens cloth. Return this lens when you've cleaned it, and replace the retainer. Make sure the convex side faces the front of the lens, and the slightly concave side faces the rear. If you put it in wrong (like I did 'cause I wasn't paying attention), you'll find that it won't assemble properly. It likely won't work well, either.


Unlike many lens designs, the front element cannot be accessed by unscrewing the name ring from the front of the lens, and then pulling the element out. I learned this the hard way (I'm a slow learner), so now the ring is all scratched up. I managed to avoid damaging the glass, at least.

 

[BJ Bignell]

Next, we're going to remove the aperture assembly and rear element from the focussing helicoid. To do this, first remove the aperture ring from the lens by undoing the three grub screws and lifting it off.



You'll see the brass ring that is connected to the aperture assembly.
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Second, undo the three grub screws on the focussing helicoid, directly above the focus ring.


Once these are loose, the entire assembly can be screwed out from the helicoid.

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[BJ Bignell]

Now, let's take a look at all of the parts we have so far: The lens barrel with helicoid and focus ring installed, the aperture and rear lens assembly, the front groups, and the aperture ring.


Next, we're going to remove the aperture control ring so that we can clean and lube it. Remove the two brass screws from the brass aperture control ring, and set them aside.

Lift the brass ring off of the assembly. The inside of this ring should be cleaned thoroughly, as should the assembly where it turns. After cleaning, apply a very light coat of grease to the inside of the ring and to the ring seat (be sure not to get any into the aperture mechanism), and replace the ring. Replace the brass screws.

Also included here is a detail of the aperture assembly. You can see that it is a 13-bladed aperture, which should give very smooth, round out-of-focus highlights ("bokeh" for all you nuts out there 😉 ).

 

[BJ Bignell]

Now that the aperture is working smoothly, we need to remove the helicoid, and get the focus mechanism sorted out. First, loosen the focus ring by undoing the three grub screws at the top of the ring.


When the ring is loose, it will spin freely. It is slotted, and should drop down over a retaining screw in the barrel.


You can now freely remove the helicoid by turning it out.


Don't worry about how it was screwed in, or about marking anything; it only goes back together one way! And finally, the two parts side-by-side.


The threads in my helicoid were originally very gummy and dirty. I used q-tips and a 95% ethanol compound to remove the grease. If I were to do it again, I'd have used an old toothbrush, and done a real bang-up job of cleaning it out. Make sure to clean the threads on the helicoid, and on the inside of the barrel.

 

[BJ Bignell]

This is a good time to take off the focus ring, and to take stock of our parts. First, remove the brass retaining screw from the top of the barrel, and then lift off the focus ring. Replace the retaining screw so that you don't lose it.


Now, let's look at our parts: The nearly-naked lens barrel, the focus ring, the rear element and aperture assembly (at rear), the aperture ring (at front), the front groups, and the focus helicoid.


Now, you can re-grease the helicoid and the barrel. Use a finger or a rubbery tool (don't use a q-tip, the cotton fibers get everywhere) to apply grease to the threads. Insert the helicoid (doesn't matter right now if it's the "right" way) and twist it in and out. Remove the helicoid, and check for dry spots. Apply grease, etc.

I used a white lithium grease as lubricant. It's supposed to have very strong resistance to running/separation, and is very smooth. I did this upon the recommendation of the Kiev Survival site. However, the brand I bought (not Loctite brand) is a little smelly.

 

[BJ Bignell]

Well, that's all I have time for tonight! 🙂

I promise to return soon with some handy reassembly tips. Please let me know if you have any questions, or if something I've written is unclear; I'll do my best to make it right!

G'night!

BJ

 

[bmattock]

Wow! Fantastic writeup! I only took the lens elements out of mine - didn't take them down farther than that! I can't wait to see what kind of images you get from it!

Best Regards,

Bill Mattocks

 

[BJ Bignell]

Alright, I'm back to finish the job. Before I get started with a few reassembly tips, I wanted to mention one more thing: When you have removed the inner barrel that contains the aperture assembly and rear element, it's easy to remove the rear element for cleaning and inspection. Simply unscrew the retainer ring with a spanner wrench (or if you're a doofus, use a screwdriver like I did 😱 ).

Reassembly! It's pretty easy, as we're basically going to do the reverse of the disassembly procedure. All of the parts you have should look like the second picture in my previous post. We've already replaced the brass aperture control ring on the inner barrel assembly, and everything else has been cleaned and lubed.

First, put the focus ring back onto the lens barrel. You'll need to remove the brass retaining screw to do this, and be sure to put the screw back in place when you're done.

Next, we install the focus helicoid. Do this step with the barrel standing on a flat surface; don't try to do it hand-held 'cause it'll get frustrating.

The helicoid and barrel have about a dozen thread starts, but only one of them is the correct one. To find out which, simply pick one, and screw the lens in. If it's the correct start, you'll find that as you screw the lens in, it'll engage the focus tab at the back of the lens with a gentle click, and then screws down all the way until it bottoms out on the top of the barrel.

If you've picked the wrong thread start, unscrew the helicoid so that it just barely releases from the threads of the barrel, but don't lift it out. Continue rotating backwards until you've got the next set of thread starts lined up, and then try screwing it in. Repeat this step until you've got it right.

 

[BJ Bignell]

The next step is to attach the focus ring to the helicoid, and to test out our focus range. First, take a close look at the three grub screws used to retain the focus ring. You'll notice that they are not quite evenly spaced around the ring, two of them are closer together. Identify the grub that is further from the other two, and remove it completely. Back out the other two grubs so that they don't interfere with free movement of the focus ring.

Next, identify the corresponding offset hole in the helicoid for the grub screw you've removed. Slip the focus ring up over the retaining screw, and slowly turn it clockwise until the two holes line up. Gently turn in one of the grub screws just enough to hold the focus ring in place; don't screw it in all the way. Do the same with the other grub screw. Finally, get your third grub, and put it in. If you've done this right, all of the screws will easily turn into the focus ring until they are flush. If you've done it wrong, remove only one grub screw, and try again. Remember to turn clockwise; if you turn the focus ring counter-clockwise, you'll also cause your nicely greased helicoid to rotate. Once you've got it right, incrementally tighten the three screws until they are just gently snugged down.

Once the focus ring is in place, ensure that the helicoid is turned all the way clockwise (screwed down). This is your infinity focus, and the infinity mark on the ring should line up with the focus mark on the barrel. Turn the focus ring until it stops. It should make almost one complete turn, and end up focussed at just short of the five foot mark.

If the focus mark does not line up to infinity and (almost) five feet, you've probably got your focus helicoid in wrong. Remove the focus ring, and try again. If the focus helicoid doesn't stop at just short of five feet, you've forgotten to put the brass focus retainer screw back into the barrel after you placed the focus ring.

 

[BJ Bignell]

Next step, install the inner barrel assembly with the aperture and rear element. Again, there are three grub screws to hold this in place, and one of them is offset from the others. Back off all three grubs, identify the offset screw, and remove it.

Place the inner barrel into the helicoid, and carefully get it threaded. Screw it all the way down until it bottoms out. Now, looking through the hole where you've removed the grub screw, slowly unscrew the inner barrel until two holes line up correctly. Gently turn in one of the other grub screws, and ensure that it turns in all the way; it must be flush with the outer edge. Don't force it! If it doesn't go, you've probably picked the wrong hole. Back it out, and try again.

When you've got the inner barrel lined up, there should be a small gap of about 1mm between the brass aperture control ring, and the top of the helicoid. Re-insert the grub screw, and incrementally tighten all three until they are snug. Again, don't over-do it, and ensure that all three are flush with the outer surface. If any of these are sticking out, everything will be out of alignment, and you won't be able to get the aperture ring on.

These steps can be a bit fiddly, and if you're anything like me, you don't have much patience. :bang: If you're getting frustrated, and just can't get it to work, now is a good time to stop and get a drink. Don't get mad and hurl the lens across the room; it's a heavy piece of equipment and you'll hurt someone.

 

[BJ Bignell]

Your lens should be partially assembled, and look something like the picture below. That means you're doing it right. If it doesn't look like that, you're doing it "different"!

Next, we'll install the aperture ring. In this case, I'm not certain that the screws are offset (I just can't tell), but if you try to install this part wrong, the aperture numbers won't line up with anything.

Remove one grub screw from the aperture ring, and loosen the other two. Slip the ring onto the lens assembly with the aperture marks pointing up (like in the picture). Slip it around - mine doesn't move easily, probably because it's slightly out-of-round - and find the correct hole for the grub screw. Gently snug the grubs down so that they're flush with the grip, and you're ready to go on.

 

[BJ Bignell]

(All this writing makes me thirsty.... Ahhh, a nice cool vodka-seven. That's better! 😀 )


The final steps! First, make sure that you've got your front element installed correctly, with the convex surface facing forwards. Screw the first and second groups together, and make sure they are firmly tightened. If you have the front element in backwards, it will contact the front of the second group, and prevent proper installation.

Next, screw your assembled front groups into the lens barrel. Screw them down tight (not Hercules tight, though), and ensure that the aperture mark on the front group is somwhere within the aperture range of the aperture ring. The ring should easily indicate from 3.8 to slightly past 22. If it doesn't, you've got one of the following problems:

• You've installed the aperture ring incorrectly.
• You've installed the front groups incorrectly, or there is something preventing them from being screwed in fully.
• You've installed the front element backwards. Yes, I did this the first time. It can happen to you!

Now, if it's all lined up, and it focusses nice and smooth, you should have a nice 13.5cm lens in your arsenal, cleaned up and ready to use. Stand back, and admire your handiwork. You did it!

I have some sample pictures taken before I cleaned the lens, and I'm still finishing the roll of "after" pictures. When it's all done, I'll scan in some samples for posterity.

Thanks for taking the time to read this. I value any comments or questions you have, and I'll gladly correct any errors you find. If you have any personal experience or other suggestions to add, please do so. The original post that got me started looking for this lens is here.

Enjoy!

 

[BJ Bignell]

And finally, some pictures!

And finally, some pictures!

Alright, I received the sample pictures and finally have a little time to go through them. First, let's post a sample from the Colinar from before the repair. You can see the effect of the haze in the low contrast.



To illustrate focal length, I've also attached a shot from the same spot, using the CV 75 lens.

 

[BJ Bignell]

Next, some shots from the Edmonton Bicycle Commuters. The first shows some bike frames, but the focus is off.



I've attached a copy that highlights in red where I though I was focussed, and in blue where I was actually focussed. The lens seems to be focussing just slightly behind where indicated by the rangefinder.




The third shot shows some flare from pointing directly against the sun, but still good colour and sharpness. I don't recall where I was focussing in that shot. If it was on the purple bar, again it would seem to be focussing incorrectly. If I was focussing on the red "Mountain Tour" bike, it's dead on!

 

[bmattock]

I'm highly impressed with the improvement. I have a Kyoei Super Acall that seems to exhibit the same problem with slight focus error, but my Arco seems to be dead on, which is nice. Great series and thanks for posting it!

Best Regards,

Bill Mattocks

 

[BJ Bignell]

In this next picture (of these terribly creepy dolls), the focus is dead accurate. I took this picture with the lens jammed (at an angle) through a chain-link fence, and am honestly impressed with the results.



The next picture was taken from my apartment deck, and despite being really boring, it showed me a lot about this lens. I'm almost certain I was focussing on the back of the rectangular road sign in dead center, yet that's not what's in focus. (I chose the road sign because it's a little less than half-way between where I was standing, and the white house in the background.) It is pretty easy to see on the slide (maybe not as easy in a web image) that the plane of focus landed directly on the rear-end of the black Sunfire, not on the sign.



In the third picture, taken from about 20' away, the tricycle is almost exactly in focus. Not much else to say about it.

 

[BJ Bignell]

And, a conclusion...

And, a conclusion...

I have other samples of pictures showing the lens being focussed behind where I was expecting, but I won't bore you with them (unless you ask really nice 😛).

The focus appears to be off, but despite every effort, I have not found any other way to re-assemble this lens other than the way I've described above, so it has to be something else. I think the problem lies in the camera; the viewfinder on the Bessa R is 0.68x with an EBL of about 25.16mm. That's not very long. The movement of the focussing tab on this lens is from 50' to infinity is almost imperceptible. Therefore, I don't think that the short baselength of the R, along with the built-in manufacturing tolerances, is sufficient for focussing this lens at more than 50', and I'm probably better off keeping it under 20'.

I bought this lens primarily as a curiosity, and it was cheap, but I also wanted to have a long portrait lens just for fun. My conclusion is that this lens is a decent performer, providing good colour and adequate sharpness, despite the missing/damaged coating on the second element. Keep the focus under 20 feet, or use it on a camera with a longer EBL, like an M3 (VF 0.91x, EBL 62.33) or maybe a Bessa T (VF 1.5x, EBL 53.7). If anyone out there wants to donate an M3 for testing, I'd be glad to give it a try! Don't be shy, it really wouldn't be a bother! 😀

I hope you enjoyed this, and that it was useful. If you have any questions or comments, I'd love to hear them. Thanks for reading.

 

[back alley]

bj,

if you want to, i have a canon 7 you could use for a test.
it has framelines or a 135.
but first you would have to remove the top and glue the light gathering window back into the frame.
but then it would be ready for testing your lens.

just a thought...🙂
joe