BrianSVP
Joined: 09 Jun 2023
Posts: 644
Location: Philadelphia
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 Posted: Sun Jun 14, 2026 12:19 am Post subject: Full Refurb/Facelift Sun SPARON 8.5cm f/2 (LONG/MANY IMAGES) |
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Posted: Sun Jun 14, 2026 12:19 am Post subject: Full Refurb/Facelift Sun SPARON 8.5cm f/2 (LONG/MANY IMAGES) |
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BrianSVP wrote:
OK, as I promised in the "What's the latest lens you added to your collection" thread, without further ado, here is my writeup on refurbing an example of the ultra rare Sun Sparon 8.5cm f/2 lens.
Background
There is one other thread on this lens here on MFlenses from about a decade and a half ago. Searching Google turns up that lens, one that was auctioned odd some time back, and one currently on sale in Moscow for several thousand dollars. That's it.
What we know about the lens:
- It's extremely rare.
- It was produced by Sun Optical sometime in the mid 1950s. I've seen one reference to 1957.
- It was produced in both m42 and Exakta mounts
- It's a 2 ring preset
- it has been suggested that it -may- have initially been designed as a cinema lens, but its 2 ring preset design suggest a designed stills application.
A visual inspection of the lens's overall exterior construction suggests it has a barrel build similar to European contemporaries.
I found this lens in an odd lot of older lenses I won at auction - I recognized it as an interesting lens based on the photos, but I could also tell it looked to be in bad shape.
Upon receiving the lens, my suspicions were confirmed. The lens arrived with several apparent major problems:
- The exterior was in awful shape. It was very dirty and covered in yellow, hardened lubricants, and the anodized aluminum surface was rough and pitted
- There was significant denting to the filter ring in multiple locations
- Despite being covered in dirt and oil, it was apparent that the front lens element had many cleaning marks, and that the rear had at least some, too.
- The aperture was seized
- The focus could turn, but it clearly had lost all its lubricant, and was stiff and gritty
- It had clearly been worked on clumsily in the past, as all the screws and visible retaining rings had tooling wear
What We're Working With
Here are some views of what it looked like, as received:
Before setting out to work on it, I realized that it had an interesting bayonet adapter over top its Exakta mount, which was removable by turning the black knurled ring. I haven't IDed the mount for the adapter yet, but will take some measurements/test on some bodies at some point and report back
Dent Removal
And now to set to work. Let's start with that denting in front:
To remove the denting, I used my usual tools, namely, a jeweler's hammer, and an aluminum lens vise:
Since I already explained how I bump out dents in a reply to stevemark in the other thread, I'll just quote that here:
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The way to use this isn't simply to pull the dent out. If you try to use it that way, you will simply pull the circular filter thread into an oval, as you have experienced.
The key to using one of these effectively is to employ it with the other item in the picture, a soft-faced jeweler's hammer. That way, you are fixing the dent the way it was created - with sharp force, rather than trying to tug it out.
What you want to do is to find the side that is closest to your lens in diameter, and snug the tool up into the thread so the top of it is against the dent, with the ridges in the thread if possible. Don't torque it to the point that the barrel is getting distorted. Then tap the dent with the hammer.
The barrel will become looser on the tool as the dent is pushed out - adjust the tension as necessary as you go along to keep things tight. On larger dents, it can help to work from the edges inward.
If you can't line up the tool's ridges with the threads, you can protect them from getting gouged by placing a thin strip of neoprene between the edge of the tool and the barrel. I cut these from pieces I pick up at a craft store for about a dollar a piece. One piece will make hundreds of strips.
If when you are done, the barrel is bulging out at any point, this can be remedied by rolling the barrel along a firm, but not too hard surface. Think wood or formica.
It's a bit of an art - sometimes you have to go back and tweak to get things to perfectly round. |
Here are the results. The barrel is now nice and round, but the thread is still kinda thrashed. I'll address that later.
Front Barrel Disassembly
Next, let's remove the front barrel piece:
This is removed by taking out these three set screws from the sides
Now it just slides off.
Looking down into the barrel, you can see the hard stop for the aperture open/close ring. There is a corresponding cutout at the bottom of the removed barrel piece.
Next we'll remove the front cell by turning counterclockwise:
This reveals the 16 aperture blades. Look at all of 'em! They were Rusty, and the blacking had been rubbed off. The assembly is held in with a wire circlip. We aren't going to do this just yet, though. Let's work further on the barrel:
At the top of the lens, we now are left with the open/close ring.
It can be jiggled out, and there is a rather large spring behind it. Note the glue on the screw on the next ring below (the preset ring). This is important.
Here are the cutouts at the side of the ring that interface with the glued screw above to set the different aperture positions.
Rear Barrel Disassembly
At this point, no further barrel disassembly from the front was possible, so I moved to the rear of the lens. I first removed the three set screws on the aluminum ring ahead of the base.
Here they are:
Removing the screws allows the mount to be pulled out, revealing a lot of nasty, dried grease, and several human hairs! YUCK! Also note that the helical synchronizer keys are built into the chrome mount!
I next took the screws out of the focus ring:
Here they Are:
Hmm, it is not coming off, nor is the ring below it. Taking a look at the lens construction, I realized that I would need to slide the mount back in before I took the next step, so as to realign the relative position of the helical halves at infinity:
Instead, I took a look further in. Note the two sets of spanner notches next to the rear element. the outer one, which has been chewed up by the previous repair, is the one I am after.
Again removing the mount and taking care not to turn the helical, I turned the retaining ring clockwise to remove it:
Now off comes the bottommost outer ring:
Oh, and hey, this has the infinity and minimum stop built into the other side of it. On reassembly, this can be adjusted by positioning the silver ring before tightening the notched retaining ring down.
And now, the focus ring comes off, too.
I can now see the inner helical. It's an aluminum-on-aluminum design. Not my favorite, since they tend to grit up and damage themselves much more readily than aluminum-on brass ones do.
I inscribe a cross mark ("Judas Mark") on it below the index line on the DOF scale to mark the infinity position.
And now let's turn it off. I also inscribe an arrow to note the insertion position of the helical.
Also take a look at all of those set screw marks on the outer helical. The ring has obviously been adjusted a few times. More on this later.
Thankfully, the helical doesn't look thrashed. There do appear to be two different types of grease. Note the grayish dried grease on the outer surface and the browner grease in the threads. I suspect the gray is original, and the brown was slathered on top of it during a previous "service."
OK, onto the DOF scale ring. This has three oval headed countersunk screws.
Here they are:
This slides off. Hey, there is a set screw lining up directly with the index mark, so no need to inscribe another mark! Also, more human hair!
Look at all that grease that migrated out around the seams! Also, look at the scuffing to the right. That was caused by the focus ring being misaligned on the previous repair.
The aperture open/close ring now slides right off, too!
Optical Groups
OK, the barrel is now fully disassembled! let's get to that rear group. Turning by the chewed up spanner notches drops the whole rear cell out.
Also, while we are here, note how the keyways are cut right through the helical. This was a common design in mid-century cinema lenses, which I suppose supports the speculation that this lens might have cine DNA.
And here it is: the threads are full of dirt and dried grease.
Removing both retaining rings allowed the front and rear elements to drop out. Both were planoconvex. At this point, I could see that everything else was swaged in and couldn't be removed.
Looking closely at the reflections/seams of the inner elements, it appears that both front and rear cells have a cemented doublet. So, classic 6/4 double gauss design.
Now it's time to bust out the ROR! After getting everything cleaned up , I set the lens elements aside
Refinishing the Barrel
Now, we return to the barrel. I used a mix of dish detergent (Dawn) and Bar Keeper's Friend on an ultrasonic toothbrush to remove the oil and grime . Bar Keeper's friend is a mix of microscopic soft glass beads and oxalic acid. It is extremely effective at cleaning metal surfaces without being overly abrasive. NOT suitable for cleaning helicals, though, since the abrasive can get caught in the little channels and cause roughness.
Unfortunately, once I got the grime off, the extent of the oxidation and pitting was revealed.
Here I had to make a difficult decision. Leave the lens as is, or do a refinish. I ultimately decided to re-anodize the surface.
Most aluminum lenses have a hard anodized finish. What this is is a clear layer of oxide that is deposited electrolytically. It is much harder than the underlying raw aluminum, making it much more durable. It is also, prior to sealing, full of tiny microscopic pores that can accept dye. This is how most lens barrels are colored black, although some manufacturers, notably Canon and Nikon, would apply black paint over top the anodized surface.
Those who know me around here might be familiar with some of my custom lens refinishes whereby I strip and reanodize black lenses to a silver look. I could use the exact same process on this lens to rejuvenate the silver-colored surface.
A highly abridged synopsis of the process is as follows:
- Clean the parts, then strip the existing anodizing with a highly caustic (Lye/Sodium Hydroxide) solution. This leaves a bare metal surface.
- Apply any surface treatment such as polishing/texturing.
- Run an electric current through the parts in a highly acidic (Sulfuric Acid) solution to deposit a new hard oxide layer.
- Dye if desired and reseal the surface in a heated chemical bath .
I've been doing this process for a decade and have done many lenses this way, and I've come to realize every lens is different, and there is a lot of art in getting each piece of each lens just right. This one had, how we say, some hiccups.
Sorry for no pics of the anodizing, but as I was wearing rubber gloves and dealing with dangerous chemicals, I didn't want to have to deal with the camera.
I immediately realized that this lens might be challenging when I dipped the pieces in the caustic solution, and they came out totally black. This is a sign of low-grade aluminum alloy. Japanese lenses typically use only higher grade aluminum and come out of the bath shiny white. The only other lenses I've seen come out black like this were all Eastern European. Just goes to show that apparently Japan's aluminum smelting quality improved rapidly between the 50s and 70s.
I've successfully managed this kind of situation ("smut") before by hitting the pieces again with Bar Keeper's Friend to remove the majority of the smut, and then dipping in a chemical brightening/desmutting solution. Since the anodizing is removed, the surface is softer, so the abrasive smooths it down to a nice semi-matte finish.
Everything looked good, so while the anodizing was gone and the metal softer, I took the time to recut the thrashed filter thread. I did this by using an old 55mm filter with thread cutting oil applied to knock out the gross roughness, then applying an aluminum (Mother's Mag And Aluminum Polish, available at auto parts store in the U.S.), and turning the filter back and forth to lap the threads until everything turned nice and smoothly.
I then gave everything another nice cleaning (oil is the enemy of consistent anodizing), and sent them through the anodizing bath:
Hmm, this doesn't look right. Notice all the black and gray staining, particularly in the knurling on the rings?
In the past when I've encountered this kind of problem, and desmutting prior to anodizing doesn't clean it up, I've realized that a glossier polish tends to prevent these kinds of impurities from manifesting in the finished product. Since I didn't want to do a ton of mechanical buffing, which can decrease the sharpness of the engraved lettering, I went with more Mother's Mag, a microfiber terry cloth, and a lot of elbow grease. Since the knurling can be difficult to polish, before using the cloth, I cleaned the knurling with Mother's Mag on an ultrasonic toothbrush. After that, everything was by hand.
After about an hour of polishing, I was satisfied with the overall appearance (there were still a few areas where the corrosion pitting was deeper and faint scuffing, but I didn't want to polish too deep and start to affect the lettering).
Back into the bath it went, and success, a clean anodizing!
I then heat sealed it, and hand repainted the lettering.
Looking a lot better, isn't it?:
Aperture Cleaning
OK, back to the mechanicals. I decided to do the aperture next. To disassemble it, we need to remove these two screws (this pic is from after cleaning). The top one is attached to the moving outer ring of the iris and interfaces with the open/close ring to move back and forth.
Here is the aperture disassembled. An important thing to note is that the ring with the lower pivots drops out after you remove the smaller, lower set screw! This makes reassembly WAY easier, since it can be done outside the lens and dropped back in as a single piece. You've never felt frustration until you've tried to use a set of tweezers to reassemble 16-20 aperture blades deep inside a lens barrel where the pivots don't drop out!
I cleaned the blades in solvent, and the aluminum barrel/helical and pivot rings with dish detergent and an ultrasonic toothbrush.
The blades are steel and had some rust and rubbed bright areas. I was able to mitigate this a bit by applying gun bluing to the clean blades, but with only partial success - they got a bit darker, but there was still some brightness showing through. The best/most tedious/most dangerous way to restore blades like this is to individually polish them down to bright metal and then apply bluing, but I didn't want to add several more hours to the repair. Maybe at some point, I'll pull it back apart and do it if I'm feeling ambitious.
There are a million examples out there about showing the reassembly of aperture blades, so I won't go into them here, but here are the blades reassembled.
You'll note I applied a couple of drops of light oil. These preset apertures with many blades are intended to be oiled. I've known people who have stripped the oil from them thinking it has come from the helical. This is not necessarily the case. If the blades are left dry, they can bind and destroy themselves if the ring is turned too hard! Later automatic diaphragms use fewer blades to decrease friction and dispense with the oil to prevent drag.
Rear Reassembly
OK, now to reassemble the barrel! We'll apply a smear of white lens grease around the area where the open/close ring goes to make sure it moves smoothly
Here it is back in place:
Now, let's reattach the DOF scale, with the index mark aligning with the aperture set screw.
Going slightly out of order here, but remember my comment much earlier about the glued screw? Well, I had removed it for anodizing (it is brass, non-aluminum metals in the bath are bad news), and when I went to reattach it, it wouldn't thread in but simply spun, hence the need for glue. Don't know if this was factory or damage from the previous repair, but I reglued it more cleanly.
Now let's grease up that inner helical. Let's not forget the keyways!
We relube and reattach the outer focus helical using the marks made before to align it.
Now we can reattach the focus ring. Remember how there were a bunch of marks on the helical surface from the set screws? Well, the ring floats up and down on the inner helical, so it must be carefully aligned by hand. Otherwise, the focus ring will drag against and scuff the DOF scale ring, which is clearly what happened on this one. The deepest divots turned out to be the correct/factory ones.
OK, lets grease up the mount. Since the helical slides up and down it, you have to grease the whole surface.
OK, time to replace the rear group. I've screwed it in and put some black paint on the thrashed spanner notches to decrease reflections.
Now look deeper in - see that infinity stop?:
We are going to set the lens to infinity, then drop in the bottom ring. Turn it so the end of its cutout is against the infinity stop on the focus ring. Now replace the black retaining ring. Don't overtighten, or the focus ring won't move.
Now we slide the mount into the keyways, making sure the bayonet isn't upside down. Tighten the screws, and the rear is done!
Front Reassembly
OK, let's go back to the front and drop in the big spring.
This part is a bit tricky. The preset ring and spring are held down by the front cell. I've cleaned the cell and blown out the lens interior and am ready to place it. Compress the spring using the preset ring, and carefully screw in the front cell.
We'll line up the preset ring with the red dot like so.
Now we reattach the front barrel, making sure to line up the cutout on the so the the open/close ring can't move when it is at f/2.
We tighten the set screws, and the lens is DONE (minus, of course, the inevitable adjustments to the focus ring)!
The Finished Product
And a few more beauty pics, just for comparison's sake
Thanks for bearing with me through all the text and 65(!)+ pics, but I hope you have found this little exercise of major (and cosmetic) lens surgery interesting/edifying.
If you are one of the handful of people who own this lens, maybe you will find it helpful, as well!
I'll be back at some point to post some pics taken with this lens.
Last edited by BrianSVP on Mon Jun 15, 2026 1:32 pm; edited 2 times in total |
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What a rescue! Heart worming really!