Really Getting In Touit

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A couple of weeks ago I posted my impressions of the Zeiss 32mm Touit lens for NEX cameras, based on a copy loaned to me by Zeiss, USA. Now that we have our own copies I can be, shall we say, a bit more aggressive in examining the lens. Not to mention getting an opportunity to continue my string of aggressively bad pun titles (which Drew absolutely hates). But, hey, don't blame me. I didn't pick the name. I just do what has to be done. I have yet begun to pun.

Anyway, given that a lens with electronic autofocus and aperture control was something new in the Zeiss consumer lineup, Aaron and I couldn't wait to take a look inside and see how things were put together. Once we got a look inside, we found there was more Touit than we expected (don't say I didn't warn you). The lens is put together solidly in typical Zeiss fashion.

Outside examination of the 32mm Touit shows us the polymer barrel with metal mounting ring. Things appear solidly built and the focus ring, particularly, moves smoothly like a larger SLR lens (many mirrorless focus rings are loose and sloppy).




The rear light baffle is a separate piece mounted by three screws.

The rear mount then removes in the usual way.  Underneath the rear mount is a thick metal shim or spacer.


It seems rather thick to be a standard optical shim or adjustment for the difference in Fuji and Sony flange-to-sensor distances (which are only 0.3mm different), so I assume it is there for added structural rigidity.


With the spacer removed we can see the rear barrel of the lens is attached by 3 large screws and an additional two screws hold the rear PCB (circuit board) in place. This is typical sturdy Zeiss construction; the screws are longer and thicker than what you usually see in lenses of this size. At 10 o'clock you can see the silver cylinder of the DC motor peeking out from under the PCB, with the large flex connector from the PCB board heading to it.


Removing the rear barrel exposes the inner barrel and PCB board. The white ring you see on around the barrel serves as a bearing to make rotation of the focus ring on the rear barrel smooth. Again, one of those 'well-built' touches. It's that smoother, tighter fit that keeps the focus ring from feeling loose and sloppy.


In a closer view you can see the notches along the focusing barrel and the optical position sensor it uses. (NOTE: after I published this a person more knowledgeable than myself corrected me - this is a hall sensor, not an optical sensor, but the purpose is to sense the movement of the manual focusing ring.)


After the PCB is removed the position sensor can also be removed.


Which lets us remove the DC motor. I will admit, when Zeiss stated they went with a DC motor because they wanted a more powerful motor to move the focusing quickly, I was skeptical (and still am, a bit) but this is quite a large motor for such a small lens. If I read Zeiss' technical description properly, focusing involves moving the entire optical assembly in one direction and possibly the rear floating element a different amount, so a large motor probably is required.


At this point it's time to turn the lens over and start working our way in from the front. The makeup ring is removed (the liquid you see is some alcohol used to soften the glue) which exposes the screws holding the front barrel in place. Again, oversize screws with coarse threads that felt very secure.


The filter ring barrel comes off after removing those three screws, and that lets us also take up the focusing ring.


These next three screws let us remove the front mounting plate. Notice how they've designed these thick mounting plates front and rear that accept all the attachements of the outside barrels (and therefore accept the direct stress when you drop the lens, etc.)


After we've removed this plate, the actual optics of the lens come out as a unit. So all of this dissection, layers of barrels, multiple screws, etc. are simply to handle the housing. The optics now come out in an entirely separate unit. This is quality construction.


The halves of this inner housing are held together with another nice touch. Three sturdy post screws, but each screw has an associated spring and washer. If I'm understanding their purpose correctly, it should maintain even  tension, broaden the area where pressure is applied and help avoid overtightening. Like several other things we've seen in this lens, they could have saved a few bucks by using a simple screw and few people would ever know. I point these things out because sometimes the insides of higher-priced lenses do show us a bit about why they're higher priced lenses.


With the innermost barrels separated you can see the aperture electronics at the bottom of the lens in the picture below. There also appears to be a second, magnetic, position sensing strip that Aaron is pointing to with the screwdriver . . .


Matched to a second position sensor (again, Aaron's screwdriver pointing to it).


I'm guessing the outer system is to sense turning of the manual focus ring for the fly-by-wire focusing system, and this one is the actual autofocus position sensor, but I could have that backwards, or just be totally wrong. With my luck this is some kind of secret-monolith tampering sensor that sent a signal to Germany the minute it was exposed to light, making sure they don't invite me to any more lens releases.

Credit: 2001, A Space Odyssey.


We did not open up the optical elements for a couple of reasons. First among theses was the fact that we were much more interested in the electronics and focusing system. After all this is Zeiss' first autofocus (and for NEX electronic aperture) lens. I don't have any questions Zeiss makes great optics but I was interested in seeing what their electronics looks like.

Second was the very thorough construction made it take a significant amount of time to get to this point and we have to put this back together and get to our daily repair work. Third, the 32mm Touit, like many wide-aperture lenses in this focal length, is based on a classic double-guass design with only 5 groups. There is rarely much to see or adjust within the optics of theses type of lenses and most of the elements will be cemented or solidly encased in groups.

Optical diagram of the 32mm Touit


In fact, the 32mm Touit is really just an optically improved version of the ZM 50mm Planar (there are some changes in the 6 elements that make up the double-gauss design and the addition of a rear group, probably for aberration compensation and perhaps as a field flattener and / or floating element.

Optical diagram of Zeiss ZM 50mm Planar



This thing is built well. Those of you who have misgivings about polymer (rather than metal) construction in a lens of this size, put those to rest. It's built like a Zeiss; I expected no less. I was a bit skeptical about the choice of a DC motor to provide more power, but I have to say, they definitely chose a large, powerful motor, so that was probably just me being cynical.

The overall construction and design were very solid, reminding me of a Zeiss or Leica rangefinder lens; much higher construction quality than many of the E mount lenses I've opened up.

I should point out that I have not yet opened up a Fuji-mount Touit. It will be interesting to see the differences between the two (aperture control being the most obvious). I also don't want my remark about E mount lenses above to be carried over to Fuji. I have less experience looking inside Fuji lenses, and to be honest find them a bit strange, but they are well constructed.


All photos copyright Roger Cicala and Lensrentals.com, 2013 unless otherwise noted. (You may reproduce them as long as the copyright credit is given AND links back to this article.)

Roger Cicala and Aaron Cosz


June, 2013


I think it important that anyone who writes an opinion on any item should be very clear in stating what, if any, benefits they received that might influence them concerning that item. (You hardly ever see me mention any, because I hardly ever get any). In this case, however, Zeiss USA loaned me E-mount 12mm and 32mm Touit lenses for two weeks to test and review. They also invited me to the press release of the Touit lenses in New York and payed for one night's hotel room there. 

41 Responses to “Really Getting In Touit”

Hervan said:

Since you said you have less experience opening X mount lenses, why don't you open both lenses side by side when you touit? (hehe, sorry)
By "both" I mean the X mount Zeiss and the equivalent Fuji: 32mm Zeiss with 35mm Fuji, and 12mm Zeiss with 14mm Fuji. (Just a suggestion.) :)

LensRentals Employee

Roger Cicala said:

Hervan, that is exactly what I plan to do.

Florian said:

Do you have any word on whether and when a firmware update will be available for the touit e-mount lenses that will allow for phase detection autofocus to work on the Nex-6?

Peter said:

Nice article.
Reminds me to not try this myself, because of the lack of thr right tools and patience.

Also remarkable that you mention the benefits you received.

bluto said:

Those last two elements look a little like a focal length reducer, potentially.

KyleSTL said:

I know Canon lenses use JIS screws, have you found that most manufacturers do? The screws in the pictures appear to be JIS (not Phillips head). Do you have any suggestions on tool manufacturers for a good set of JIS screwdrivers? I've killed a few #000 and #00 Phillips over the course of the past few years repairing lenses and cameras, and I think I'm ready to buy the right tools.

Kirby Krieger said:

Just a heart-felt "Thank you!". Superbly done.

Dave said:

Mr. Cicala, can you please elaborate why you stated that this is Zeiss's first autofocus lens? As far as I know, Carl Zeiss has been supplying Sony with excellent autofocus lenses since its acquisition of Minolta's alpha-mount camera division. Were they just providing Sony with the optics?
Thank you.

LensRentals Employee

Roger Cicala said:

Dave, it is my understanding that Zeiss has optically designed several lenses for Sony, but has not manufactured any (who actually does make them seems somewhat controversial), nor have they been responsible for the autofocus systems or other electronics. Zeiss, at the release, was also very clear that they have cooperation from Sony in E mount, but did not say a word about alpha mount.


LensRentals Employee

Roger Cicala said:

Kyle, they are all (to the best of my knowledge)JIS screwdrivers. Good ones can be hard to get in the U. S. but Micro Tools usually has a good online selection of JIS drivers.

LensRentals Employee

Roger Cicala said:

Peter, I think it's the right thing to do -- I wish everyone did it. I know just enough to make me a bit cynical and never want to be 'that guy'.

André Oliveira said:


WERA, from Germany, have Japanese JCIS bits. I bought them from chadstoolbox website.

Andrew Burday said:

"With my luck this is some kind of secret-monolith tampering sensor"... Snort. Cue timpani. "I'm sorry Roger. I'm afraid I can't focus that close."

Also +1 for being clear about your relation to Zeiss.

LensRentals Employee

Roger Cicala said:

Andrew, when I asked Aaron if he thought we could do this disassembly and get things back together in an hour, his reply was "I have the utmost confidence in our mission, Roger". That sort of set the tone.

GH said:

Great, thanks Roger! It would be cool if you opened up the NEX/Zeiss 24mm f1.8 and compared the build to the Touit.

Clive said:

How about opening one of the super cheap Sigma mirrorless mount lenses as a comparison. Optically the Sigmas offer great value for money and it would be interesting to see where the corners have been cut.

Daemonius said:

Seems Sony should let Zeiss do their ZA lens, cause build quality of ZA lens certainly isnt up to this level..

Very impressive things. As I like my regular Planar, this would be nice thing to have on NEX. Wish Samsung NX could have this. :)

Steve Hoge said:

Thanks, great report! Nice to know that it's still worth the money for a quality product.

BTW, where'd they put you up in NYC?

Alain said:

Mr Cicala, maybe you can confirm that, but I am ready to bet the notches used to sense the focusing ring position are made of plastic. As an electronics engineer, I can share this : using Hall sensors do not bring any technical advantages here. They are more expensive than optical sensors and, as they sense magnetic field changes, the notches should be made of magnetic material, which is more expensive than molded plastic... Moreover, a Hall sensor case is not U-shaped and does not need to be...

Charles said:

The Zeiss Sonnar ZM 50/1.5 is a wonderful, distinctive lens. They could do an auto-focus version for the same two mounts. I've read that 50mm is about the shortest feasible focal length of the Sonnar design, but maybe that is not true for APS-C sensors.

The lens has one quirk that holds down sales for true rangefinder cameras -- focus shift in relation to the rangefinder. That problem disappears on the Fuji and Sony cameras.

samdman said:

The fact that Zeiss/Sony put a lot of resources to make this into mass production product with such quality and everything, do you think it justify the price, Roger?

I mean the design and technology put into it, I am sure they had to designed it ground up (hence they used new family lens name instead of some -gon/other established name).

Andrew said:

Hi, are there any hints that these were manufactured by Cosina in Japan?

Fake Name said:

The person who told you the sensors on the focusing ring are hall-effect sensors was incorrect. Assuming the little pins on the focusing ring pass through the notches in the sensor bodies, that would mean that they are plain-old optointerrupters, probably arranged as a quadrature encoder.

If they were hall-effect based, it would mean that each of the little pins would have to be a magnet, to properly trip the sensors. Unless they *are* magnets, putting hall-effect sensors there wouldn't do anything.

LensRentals Employee

Roger Cicala said:


They are definitely plastic and there is no magnetic tape, so perhaps the information I received was incorrect and my original thought, that they are optical sensors, is correct after all.

LensRentals Employee

Roger Cicala said:

Andrew, no hints at all, but Zeiss has said the Touit's are assembled in Japan. That leave a number of options, though.

Ilkka said:

Thank you. Thank you very much for the time and trouble in reporting these.
I do not have that lens. I don't even have a body where I could fit it. But I am an engineer and I have been a photographer for more than thirty years, and I have a few Zeiss lenses. I find this very interesting all the same. So just sincere Thank You.

Michael Przewrocki said:

Can only be Yashica. They mentioned to revive optical production in 2012. Two german companies were on the list of potentional cooperations. It must be Yashica or a similarly called company. Experts here know the exact name.
The same company which already made Zeiss Japan lenses for Contax/Yashica.

Bruce said:

This is the best website ever!! - although that may seem a bit counterin-touit-ive...

dirk said:

I am just guessing here, but maybe Zeiss has a cooperation with Fuji for the AF. Would explain why they also make them for X-Mount. Maybe a disassembly of the XF 35mm would give a clue.
Great article!

Gerald said:

Thanks for another great article.
I agree with Alain - I think the sensors are photo-interrupters. As Mr Fake pointed out, Hall sensors need a permanent magnetic field to function. & engineers tend to hate designing permanent magnets into their products - they attract sharp, abrasive fragments which reduce service life. I have some Takumars over 50 years old & still mechanically excellent - the Zeiss engineers will be designing for similar longevity, I'm sure.

Tony Webster said:

What a legacy from Mr. Zeiss! Yes, one man (or woman) CAN leave this world a better place than as found. I suspect that the techological wizardry we now take for granted, can obscure some "holy grails" which were earned only with great effort and dedication, and sustained by maintaining the highest possible standards. Rest peacefully, Mr Zeiss; Mr. Eastman; Mr. Nikon et al; and others following. Something to appreciate when I next pick up my camera! And a tip of the hat to messrs Cicala and Cosz for a fascinating look into genius-grade design and engineering.

stevemark said:

The optical design of the "Zeiss" lenses for the Sony Alpha mount is done by Sony as well (ZA 2.8/16-35, ZA 2.8/24-70; ZA 2/24, ZA 1.8/85, ZA 1.8/135; E-mount Zeiss 1.8/24mm). Most of them are derived from previous Minolta G constructions. One can see that by comparing the construction of the Sony/Zeiss ZA lenses, the Minolta G lenses and the "real" Zeiss ZE/ZF lenses.

This doesn't say anything about the quality - the ZA 1.4/85mm is better than the ZE/ZF 1.4/85mm; even the Sony AL 2.8/85mm is better than the legendary C/Y Zeiss 2.8/85mm.

Source of this information? Personal communication with the head of Sony Alpha lens design.


Zachery said:

I don't know why you think the X versions have mechanical apertures. No X mount lenses from Fuji do. And it would not make sense to do it differently anyway since the lens has to support camera control of aperture for P and S modes. The X mount itself has no mechanical control of aperture. The ring around the lenses for aperture is just a big switch emulating the old mechanical ones. The diaphragm control is still exactly the same as NEX it's just that Sony doesn't have any support for a separate on-lens setting dial so the lens doesn't have it for that platform.

Rick Knepper said:

Sony Rumors has hinted at a full frame Nex 7. Would these lenses cover that sensor?

LensRentals Employee

Roger Cicala said:

Rick, they seem to be APS-C sized only. I would guess (and strictly guessing, I have no inside info) that they would remake their ZE/ZF line to cover a full-frame NEX. That will be the downside to full-frame, the lenses will be larger, at least a bit.


Andrew Roos said:

Thanks for taking the trouble to share this with us. As an engineer I find it quite uplifting that the lens appears to have been built well, not just cheaply! This certainly is not the case for most consumer goods today.

Dante said:

What I would like to see is a teardown that tells us whether the Zeiss and Fuji lenses have a common manufacturer. That the Zeiss lenses show up on the Fuji roadmap and that the electronics are apparently perfectly compatible suggests some degree of cooperation.

Roger Knight said:

Roger, Great job as usual, but you missed one. "Matched to a second position sensor (again, Aaron's screwdriver pointing Touit)?".
Always enjoyable and informative reading. Thanks.
Roger Knight.

hugh crawford said:

There have been plastic magnet designs for many years using magnetic material mixed with plastic, for instance the magnetic strips used on credit cards and the flexible magnets used for signs. However if you were using a plastic magnet you would not need to make the little teeth you see here. In fact the magnetic plastic used for signs makes a great encoder as it has an alternating north south magnetic fields built in. The only reason to have the teeth moulded in would be to skip the step of calibrating the the relationship of the magnetic fields to the rest of the assembly. I used to have a 1970s Burroughs Corporation (the Leica of computer manufacturers! ) Hall effect keyboard that incorporated plastic magnets in the keys.

In the past ten years a number of non-metallic organic polymers have been developed see http://en.wikipedia.org/wiki/Plastic_magnet.

I'm not saying that any of this means that Zeiss is using Hall sensors , but just because the encoder is plastic does not rule that out.

LensRentals Employee

Roger Cicala said:


There definitely is cooperation - Fuji reps were at the Zeiss Touit release and Zeiss has said they will only work with companies who give them complete access to the AF coding, etc.

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