Repair: Carl Zeiss Jena Biotar 58mm f/2 (semiautomatic)

Hello, everybody! I just had my first Corona vaccine shot and my body aches as if I had the flu. Mundane things felt like chores because my body feels heavy. I wasn’t expecting the side-effect to kick-in this fast. This is fine at least my body will bounce-back and acquire some immunity from the dreaded virus. Speaking of squeaky-joints and bouncing-back, I will show you something that was squeaky when it got to me and thanks to my efforts it was restored and it’s now fast, smooth and in a much better state than it was when I got it.

Introduction:

The Carl Zeiss Jena Biotar 58mm f/2 (semiautomatic) is a redesign of the earlier preset Carl Zeiss Jena Biotar 58mm f/2. It was made from 1953 up until about 1960. The reason for its development coincides with the newer Zeiss Ikon Contax models which could actuate the iris automatically with a push-plate near the bayonet.

The biggest difference between this and the preset Carl Zeiss Jena Biotar 58mm f/2 is the addition of a semiautomatic iris. You basically cock the iris by turning the aperture-ring towards f/2. This will lock the iris to its maximum-aperture, it will stop-down to the value that you’ve set when you depress the shutter-button. If you’re metering through-the-lens it is important to meter with the iris stopped-down, you could do this before-or-after focusing. It all depends on you. The desired value can be set by pulling the aperture-ring towards the camera then turning it to the value you desire.

It has a 6-elements-in-4-groups design that’s identical to the Carl Zeiss Jena Biotar 58mm f/2 in paper but some folks claim that both lenses perform a bit differently in actual practice with the most apparent differences happening at the corners. The minimum-focus is also different if that matters to you. There’s always a possibility that the curvature may have been revised in some way but we’ll never know until somebody shows an official document stating the changes. I am very interested to know the truth and I’m sure that all of you are, too.

Unlike the older Carl Zeiss Jena Biotar 58mm f/2 this one only closes-down to f/16, the number of blades were reduced as well so it only has 10 instead of 12. This won’t focus as close as the older version but the difference is negligible, it’s merely a few centimeters longer. The focus-throw is a bit shorter so it’s quicker to use when tracking subjects.

The Zeiss Ikon VEB Pentacon FBM and all of its variants will benefit from the semiautomatic iris the most because these all have dark viewfinders since the prism and focusing-screens are all tinier compared to later SLR cameras. It sounds a bit tedious having to cock the aperture before making every exposure but you won’t notice this much in real practice. I personally like how it handles when shooting with film but not so much when using it on a mirrorless camera. Because this has that semiautomatic aperture gimmick you could only actuate this from behind the mount when mounted. It’s important to buy an adapter that has a wall just behind the throat of the mount so you won’t have to deal with this, all you’ll need to do is just use it like any manual-aperture lens.

Learning how your lens performs is crucial to maximizing its use. You will learn how to utilize its strengths and avoid its weaknesses. This knowledge helps in determining which lens to bring on an assignment. I shot these from f/2f/2.8f/4 and f/5.6 since these are the most common apertures that people would want to use this and we’ll also get to see the most changes happen with these values. I shot these with my Nikon Z6, some of the photos were cropped close to 1:1 so we could see the details better.

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The amount of distortion is negligible but you’ll see some of it only if you look very carefully. It’s not something that I’d be concerned with.

Vignetting is rather low and you’ll only see some of it at f/2, it’s basically gone from f/2.8 which is impressive. It doesn’t look as heavy as the older Carl Zeiss Jena Biotar 58mm f/2 which doesn’t have much of it at all even at f/2.

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It flares when you have bright sources of light within the frame, you’ll also see some blobs, too. It’s not bad at all and I think it performs better compared to the Carl Zeiss Jena Biotar 58mm f/2. The coatings may have been improved, that’s the only reason why it performs better compared to the older version.

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This lens is legendary for the character of its bokeh. It’s smooth in most cases and the rendering is unique, this is one of those cases where it’s easy to identify which lens took what photo just by looking at the character of its rendering. It’s a unique look that very few lenses share with this lens.

Some people claim that the older Carl Zeiss Jena Biotar 58mm f/2 renders smoother blurs. I personally couldn’t see any obvious differences between them.

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Chromatic aberration is controlled quite well even when shooting wide-open. You’ll still see some in extreme cases but it’s not bad at all. Spherical aberration could also be seen but it does not bother me at all, it actually helps add another layer of “magic” to your photos. Stopping the iris down to f/2.8 will clean the frame, resulting in a clean-look. it looks a bit better from f/4 on because there’s not much to be improved from what we saw at f/2.8.

(Click to enlarge)

Sharpness is excellent even at f/2 and the resolution is adequate, too. The corners don’t look bad as well but it’s not as nice as what we’re seeing at the center. Sharpness improves a bit by f/2.8 and the resolution looks a bit better, too. It’s because the center already looks quite nice from the previous aperture value. I noticed bigger improvements from f/4 and f/5.6 compared to the differences we saw from f/2 to f/2.8. The reasons for this is the improved resolution and the wider depth-of-field. It’s safe to say that the center is performing at its peak at f/4, the corners don’t look bad, too.

I noticed that this performs at least a stop better compared to the Carl Zeiss Jena Biotar 58mm f/2 but both lenses do not perform as good at further distances. They’re both great at closer distances but this one is a lot better according to what I saw with my own copies.

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I think the only reason for shooting with this lens these days is to capitalize on the unique look it adds to your photos. I also like how sharp this is at the center, the rendering is very beautiful and the focus-transition is smooth. The contrast is bit too-high for my taste so the colors will look choked but that’s just part of what makes the pictures look great. The tonality is not bad at all, just not as good as what I’m used to. I consider this as a “feature” instead of a design flaw.

It’s able to render the blurry parts of your scene with a painterly-look. This is something that will make you say “Biotar” once you saw this look.

I don’t like the “soap-bubble” look at all but some people actually like this a lot. It gets stronger once you focus closer and shoot with the widest-aperture value. I can’t blame the people who gravitate towards this look because it’s unique but this is just not for me.

The background looks smooth as expected from this lens. There are difficult elements here but we don’t see any rough and smudgy look from it.

This is the worst that I could get it to render, the foliage looks terrible, giving it a cheap-look.

Exposing your scene properly will prevent chromatic aberration from looking “wild”. You’ll still see some of it here, it is hard to avoid in this scenario because the difference in contrast is just too-high.

This was shot at f/2.8, it’s very tempting to shoot with it at f/2. You should develop the discipline to help prevent you from shooting wide-open every time. Some people do this even on a sunny day.

The sharpness is amazing at f/4, it’s technically near-perfect at the center. The balance between soft and hard details is good, I love lenses that could render both aspects well in one photo.

It’s amazing how sharp this is for its age, it’s certainly able to depict the smallest details very well. The clarity, contrast and saturation all look nice, its reputation is certainly well-earned.

Spherical aberration is nice for depicting skin, even if that belongs to a sculpture of Jo. Just imagine this with a human instead of an inanimate object and you’ll get the idea. I think this was shot at f/4, spherical aberration can still be seen at this aperture when it’s really bright.

Of course, it’s also a great lens for journalism despite being a bit cumbersome to operate. Why would you buy a Leica which costs several times more when you could get great photos with a cheaper one.

The clarity of the photos I get from this is astounding and it’s best when the lighting is good. This is certainly an artist’s tool and it should be treated as such.

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Here are more photos for you to look at. This is still a relevant lens today specially if you’ve adapted it for use with the latest digital cameras. It’s great if you don’t need to shoot-fast, enabling you to focus carefully. This is a great lens for those who want to develop their own style, I see plenty of potential from it despite being older than most of us here.

Let’s now check some film photos. Film has a unique look that is hard to simulate with a digital camera thanks to grain. It reacts differently to light, this means that it could mask a lens’ flaws or amplify them. Since this was designed to be used with film, it’s best that we judge this using its intended medium.

Its name is synonymous to the “soap-bubble” effect that some people like. I personally don’t like this because it can be somewhat distracting when overdone.

Resolution and contrast is rather good which enables you to take nice pictures even when using cheap, pharmacy film. Some people may wonder why I mentioned “pharmacy”, it was possible to buy film at convenience stores, pharmacies and even the newsstand back then when film was the only practical medium for photography.

As expected, this lens renders smooth, exquisite blurs for which it became famous for. Sharpness is also nice at f/2, the structure of film’s grain helps compliment this attribute by giving you a bolder look.

While 58mm is not the best choice for tightly-framed portraiture it’s great for environmental portraits so you could put some of the background into the frame which helps add some context to your photo.

It’s also a good lens for lowlight situations specially if you’re using a slower film. It’s best to shoot with a faster film but the fast f/2 maximum-aperture is handy when you don’t have a fast-enough film loaded in your camera.

I love how this lens renders, it’s able to give you a nice balance between hard-and-soft. This property is something that I look for in a premium lens because it the photos have a nice, polite character to it.

It’s known for rendering smooth blurs but that doesn’t mean that it’s immune to rendering rough-looking details. You should still be careful with what you have in the background as evidenced by the small patch of blurry-mess you see at the bottom of the frame near the center.

Since it doesn’t have a high-amount of distortion it’s fine to use this for shooting architecture. You can still detect a tiny amount of distortion in this photo but only if you look hard.

The depth-of-field is quite shallow when shooting wide-open so you should be careful with it. The person at the end of the alley is the most important element here so I’ve decided to focus on him instead at the expense of the foreground. What this does is to lead your eyes to him instead on focusing on the clutter.

This wasn’t shot with a fast film so I had to use a slower shutter-speed, I think this was shot with 1/20s and this speed is the slowest I’d use for this lens.

(Click to enlarge)

I wasn’t surprised to see that this performs quite well with film. I think shooting film with this is the best way to enjoy it, the photos I get from it look amazing. If there’s one thing that I liked about this compared to the preset Carl Zeiss Jena Biotar 58mm f/2 is its semiautomatic aperture. I was able to easily focus with it and not worry about manually stopping the iris just before I take my exposure. This sped-up my workflow considerably and I’m sure that you’ll notice that, too.

This is just as good as the Carl Zeiss Jena Biotar 58mm f/2 in terms of performance. If you already have that then you’ll want to skip this. The only reason to buy this one instead of the older, preset version is to use the semiautomatic iris. It is very convenient but if you don’t need this feature then it’s better to buy the older Carl Zeiss Jena Biotar 58mm f/2 as it has less issues associated with adapting it to a digital camera. These are usually cheaper compared to the older one because some people don’t want to deal with the semiautomatic gimmick and its quirks when adapting it. They usually go for $120.00 but can get as high as $200.00 or more. I got this along with a beater-camera so it was cheaper. If this is something that you want be sure to check the iris, it should work perfectly. The blades should fine and not oily, too. All of its rings should operate perfectly and the aperture-ring should turn effortlessly when the iris is stopped-down. Press the pin at the mount and the iris should close instantly, if it’s sluggish or squeaky then it has to be overhauled. You will also want to check the glass as well and be sure that it’s clean and clear. A few cleaning-marks should be fine but if the marks are deep then you should skip it. It’s best if you could check the lens yourself before buying it. Just want and you should be able to find one that fits your budget and standards, happy hunting.

Before We Begin:

If this is your first attempt at repairing a lens then I suggest that you see my previous posts regarding screws & drivers, grease and other things. Also read what I wrote about the tools that you’ll need to fix your Nikkors.

I suggest that you read these primers before you begin (for beginners):

Reading these should lessen the chance of ruining your lens if you are a novice. Before opening up anything, always look for other people who have done so in YouTube or the internet. Information is scarce, vague and scattered (that is why I started this) but you can still find some information if you search carefully.

I highly recommend that you read my working with helicoids post because this is very important and getting it wrong can ruin your day. If I can force you to read this, I would. It is that important!

For more advanced topics, you can read my fungus removal post as a start. It has a lot of useful information, it will be beneficial for you to read this.

Disassembly (Lower Barrel):

This is certainly going to be a lot more complicated than any preset Carl Zeiss Jena lenses but the good thing is we can separate the whole thing down to its major components by removing a collar at the rear just like what we do normally. This will allow us to work on the barrel without having to worry about damaging the delicate front part which holds all of the complicated gimmicks employed to make the iris semiautomatic.

Having said that, this is not a lens for beginners and an experienced repairer will find this a bit more challenging to fix. I personally didn’t find this impossibly-difficult at all but I had to guess how things should be removed since this is a first for me despite having a couple of years’ worth of experience under my belt.

The barrel itself isn’t complicated but there are a couple of things that may confuse you but I’ll point them out here so you won’t have to guess how things should be dismantled. If all you need to do is to lubricate the helicoids this section should be more than enough.

Like most Carl Zeiss Jena lenses of its time the whole thing can be dismantled by unscrewing a collar at the rear. It’s the largest one you see here, the outer-most ring with the largest diameter. Be careful so you won’t scratch the glass.

Unscrew the collar and it’s possible to separate the lens into its major components.

Before you continue it’s best to measure the height of the focusing-unit so you’ll know how tall it is when set to infinity but I think I should’ve taken the measurement while the front-barrel is still connected so it also measures the depth of the innermost helicoid.

Extract this large screw carefully so you can separate the helicoids. It serves as a limiter so you can’t turn the focusing-ring beyond its range.

Carefully remove the inner helicoid and never forget to mark where it parted, this is also the same spot where it should mesh with the central helicoid. Many people forget to do this so they end up being stuck with a lens that never focuses to infinity. Read my article on how to service helicoids so this won’t happen to you.

Do the same for the outer helicoid, mine parted exactly at the infinity mark. While this looks like a single-entry thread it is still important to note where these parted.

Carefully extract this large screw to remove the pawl. It secures the aperture-ring after you’ve cocked it. Depressing the pin at the rear will release this, closing the aperture the aperture down in a swift manner as it’s spring-loaded.

Be careful not to lose the spring found here, it’s very small so it’s easy to misplace.

Scrub the helicoids with a strong toilet cleanser to remove the old grease then clean them well with alcohol to remove any residue. Polish the threads carefully so you won’t scratch them then use a grease with moderate resistance. Using a thick one will make it difficult to turn and a thin one will make it feel a bit gritty. Never apply excessive amounts, a thin film is enough. Put the helicoids back and measure them again to make sure that you’ve reinstalled them properly.

I noticed that the focusing-ring turns with a bit of resistance when the iris is cocked, it’s caused by the pawl that latches to the iris mechanism. The metal-to-metal contact causes a slight gritty sensation when you turn the focusing ring. This could be remedied somewhat by applying some grease to the pawl’s tip and the edge that contacts the long rail. Don’t apply too much, a grease which is slightly thicker than the one you’ve used on the helicoids will give the best results.

Disassembly (Front Barrel):

This is where you’ll likely spend the majority of your time as most of the complicated mechanisms are situated here. It’s not necessary to dismantle this part if all you want to do is to service the helicoids but if the iris is oily the only way you will be able to service it properly is by overhauling it. This task demands patience and skill so never attempt this if you are a beginner.

Since the optics appear to be clean I left it alone. Read my previous Carl Zeiss Jena Biotar 58mm f/2 article to see how it’s done in case you’re curious. Never dismantle the optics if you don’t have to, Carl Zeiss Jena lenses are delicate and they will require adjustment once they’ve been dismantled and the process is never easy.

This is a very complicated mechanism, overengineering is the biggest trait of many Carl Zeiss products.

The rear optics assembly can be removed by unscrewing its retainer and be careful not to scratch anything.

Unscrew the housing of the 3rd group with a special tool and be careful not to scratch the threads.

The bezel can be unscrewed with a rubber tool.

The front optics assembly can be removed with a lens spanner once the bezel is gone.

Decouple this spring before you proceed, be careful not to pull this or it will lose its tension.

Carefully unscrew this so you can remove the rail of the spring.

Pull the rail off and don’t forget which side should be facing the front.

Extract these to remove abutment of the spring.

There’s a rubber damper underneath this, be sure not to damage it. Without this you’ll feel a strong shock when the iris is closed.

The iris mechanism is delicate so be careful not to damage it. There is a retainer securing the whole mechanism, a long lens spanner helps in unscrewing this retainer.

Pick the diaphragm’s cup off with your fingers.

The iris mechanism can now be dismantled.

Examine how the iris looks so you’ll know how to put this back again later.

This is how it looks like when it’s fully-open.

These set screws secure the regulator’s adjuster. Before you do anything be sure to note its original position so you will know how it was adjusted originally. Loosen these but never remove them.

Unscrew this carefully so you won’t snap it.

Unscrew the aperture-ring everything is dismantled. This part is tricky because you’ll have to feel everything while you turn this or you risk damaging this fine mechanism. You’ll have to pull the aperture-ring down at times to disengage its screw from the slots found near the neck (tip) of the objective’s housing.

Remove and clean the springs very well because these are usually caked in grime. Do not lose any of these, obviously.

It’s a bit tricky to dismantle the 2nd spring, you’ll have to be careful so you won’t damage its rail which is made of resin or plastic. It’s brittle and irreplaceable.

Turn the adjuster to help give you space and carefully pick the spring off.

Carefully remove the spring and clean it very well. Do not pull it or it will lose its tension.

It’s tricky to remove the rail but it’s possible if you flex it a little bit.

You’re now able to remove the regulator once the rail is gone, it’s the only thing that holds this together.

Overhauling the iris mechanism takes the most time, you’ll probably spend about an hour putting the leaves back. It’s a tedious job but I’m used to it. Putting the spring back can be very tricky, you’ll have to reinstall the rail first before you will be able to put the spring back. This requires a lot of dexterity and patience.

Avoid any mechanical contact with the glass if they’re coated, blow any dirt off and that should be enough. If your lens has fungus read my article on how to clean lens fungus so you will know how this is done. Dilute the solution well so it’s not going to damage the glass.

Conclusion:

I’ve always curious as to how these semiautomatic lenses work and now I know. It certainly scratched that itch, This one took me more time to overhaul due to its complicated construction but it was all worth it. I’ve removed plenty of grime from the iris mechanism. It initially turned with a squeak but it now turns smoothly, freely and you could feel the power of the 2 springs. The damper certainly helped a lot with softening the vibrations so it won’t produced as much shake as I expected. This is what I would consider to be a lens for repairers with advanced skills, beginners should never tackle it and it’s best to just send it to a professional or you’ll risk destroying it.

There’s no way to adjust the focus so it should be spot-on so long as you’ve reassembled it correctly. If the results are off then you’ll have to trackback and correct whatever is wrong, usually it’s in the helicoids.

Despite its quirks this is a nice lens and I’ve really enjoyed shooting with it. This photo should say it all, it’s a great lens for a relaxing afternoon stroll and having a beer with a friend afterwards. Its age shouldn’t be a hindrance at all, you’re still going to capture amazing photos with it and the best way to enjoy this is to shoot with film.

Thanks for following my work, if you liked this article please share this with your friends so it will get more views. This site earns around $0.40 a day, we are totally reliant on views. You can also support this site, it helps me offset the cost of maintenance and hosting. You’re also helping me purchase, process and scan film. This site promotes the use of film so we are all in this together. See you again in the next article, Ric.

Help Support this Blog:

Maintaining this requires resources and a lot of time. If you think that it has helped you or you want to show your support by helping with the site’s upkeep, you can make a small donation to my paypal.com at richardHaw888@gmail.com. Money isn’t my prime motivation for this blog and I believe that I have enough to run this but you can help me make this site (and the companion facebook page) grow.

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Helping support this site will ensure that this will be kept going as long as I have the time and energy for this. I would appreciate it if you just leave out your name or details like your country’s name or other information so that the donations will totally be anonymous. This is a labor of love and I intend to keep it that way for as long as I can. Ric.

1 Comment (+add yours?)

  1. Brad
    Aug 27, 2021 @ 21:49:38

    What a fabulous resource you have created here Richard. I’m binge reading a ton of posts…

    Reply

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