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(un)Making Pancakes

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I've always been fascinated by pancake lenses. It just amazes me that something that small can actually function. As I mentioned in an earlier post, we've been taking things apart to determine where and how (and sometimes if) the lenses can be adjusted optically. So, I decided to do two pancake lenses for mirrorless cameras side-by-side to see how they differed (the Sony 16mm f/2.8 E mount and the Olympus 17mm f/2.8 micro 4/3 mount). I wasn't sure there would be much we could do with pancakes (and there wasn't), but I still found the look inside rather interesting.

 

Today's contestants: the lovely and talented Sony 16mm f/2.8 and Olympus 17mm f/2.8 pancake lenses.

Since everyone seemed to enjoy looking inside an NEX mirrorless camera, I decided to take more pictures while doing today's disassembly.

Optically I expected both lenses to be fairly simple: the Sony has 5 single elements, the Olympus 6 elements in 4 groups, and both have the diaphragm about in the center of the lens elements. They seem very similar as we start opening up the backs: both have 3 screws holding in a light baffle / protection cap, and 4 screws holding on the lens mount, just like most other lenses.

The Olympus (left) and Sony lenses with backs removed.

There are a couple of minor differences: the Olympus only uses 1 small screw to hold its electronic connector to the mount, while the Sony uses two. It's at this point that we found the first (and apparently only) optical adjustments. The Olympus uses washer type shims, while the Sony uses some 90 degree shims (black and white things in the picture) to space the lens-to-lensmount interface.

Removing the PC boards is more of the same, again Sony uses 3 screws (I have no idea why, no one else does) to hold the board in place, while the Olympus goes with the more common single screw.

 

Olympus Disassembly

At this point, disassembly of the two lenses gets a bit different. It's obvious in the above picture that the Olympus has several screws holding the optical assembly in the case. Take those out and slip the case off . . .

Then turn it over, pop off the plastic front makeup ring, remove the couple of screws revealed under the makeup ring  . . .

. . . . and the rest of the front rings come off, leaving the core of the lens completely uncovered.


Largely disassembled Olympus pancake (rear view). Note the focusing motor at bottom and geared teeth engaging from manual focusing ring. Smaller motor at 11 O'clock is the aperture control motor.

Two screws remove the focusing motor. The aperture control motor slips out and its flex disconnects, and now the optical elements are separated from most of the lens. The Olympus design places the optical elements in the center of a 3-armed plastic piece that connects the lens ring.

Olympus optical elements and array, with aperture motor removed. You can recognnize the purple ring and see the 5 bladed aperture, but that's about all that lets you know this was the Oly.

The entire optical assembly slides back and forth on three arms within the outer ring for focusing. With a prime lens this small there's no need for a separate focusing element.

The plastic mount for the lens core had a couple of lensmaker's marks on it. I had hoped, as is often the case, they would be associated with adjusting shims or collars, but I certainly couldn't find any. Whether the marks are some directions for orienting this assembly, somebody's signature, or random graffiti I don't know. Maybe one of you can tell me?

Sony Disassembly

Sony disassembly was initially less obvious. After the PC board was removed I had expected the front plastic makeup ring to pop off, like most do, but it wasn't budging. Re-examination didn't reveal any other way in so I tried popping the front makeup ring a little harder. This sort of worked, although it ruined the makeup ring. It turns out Sony holds it down with a ton of glue, rather than plastic pop-tabs like most lenses. Oh, well, next time I'll know to use glue remover. But once the ring was removed the barrel pieces slip right off the lens.

 

Front of Sony pancake lens with most of barrel removed. Torn up makeup ring and glue residue on plastic around the lens demonstrate this was obviously my first time opening one of these.

The lens core lifts out of the bottom case and has three screws begging to be removed . . .

. . . which lets us remove the inner optical core from the surrounding support.

Once past the front makeup ring, the Sony disassembly was quick and easy.

Separating the optical elements

Having removed all the lens parts except the optics, the two lenses look rather different: the Sony has a small, self contained optical assembly while the Olympus assembly is mounted to three arms that slide up and down through an outer ring.

 

Olympus (left) and Sony (right) optical cores.

The optical groups of both lenses, however, can be separated into front and rear components by removing a couple of screws. With the Sony lens removing the screws visible in the photo above allows the diaphragm assembly comes out as a separate piece (left side of each image below), sandwiched between the front (upper image) and rear (lower image) glass elements of the lens.

 

The diaphragm unit of the Sony lens, with the front (upper) and rear (lower) optical components.

With the Olympus, removing the screws allows most of the optics to detach in a group, with only one element remaining in the center of the plastic arms.

I had expected to see a shim or adjustment here, but there wasn't one. Nor was there one in the Sony. So as best I can determine, both of these pancake lenses have no real optical adjustments other than shims at the lens mount. But then, pancakes aren't generally expected to be razor sharp lenses.

The remaining optical section of the Olympus (left side in above image) separates neatly in two halves at the aperture. Unlike the Sony, the aperture unit isn't self contained, but rather sits on top of the rearward group. This allowed for a nice demonstration of how aperture blades are set up (in case you haven't seen it before). The right side image below shows the two rings of the aperture mechanism, with mounting posts on both the outer and inner rings. The aperture blades (one is sitting above the lens in the right illustration) mount to the outside post at the hole in one end, and the slot fits over the post on the inner ring. As the inner ring is turned in relation to the outer ring, the post moves along the slots, closing or opening the aperture.

The final pictures

Of course, I have to post the images of the disassembled lenses, first the Olympus and then the Sony:

 

Completely disassembled Olympus 17mm f/2.8 m4/3 pancake lens.

Completely disassembled Sony 16mm f/2.8 E-mount pancake.

These are the smallest and simplest lenses I've ever taken apart. The front element of a 70-200 f/2.8 lens is larger and heavier than either of these. The small size of the glass elements is really shocking: even the rear element of, say, a 50mm f/1.4 lens contains more glass than all the elements in either of these. Despite the fact it has to cover a larger sensor, the elements in the Sony lens aren't obviously larger than those in the Olympus.

The simplicity of the design shows why these lenses rarely break. And since optical adjustment isn't an option, apparently, there won't be a lot of reason for me to do this again. Which is too bad, really. It's a nice, straightforward disassembly, with a simple internal design.

And before someone asks: yes, I can put them back together :-)

But the Sony lens will have to wait until I get a new makeup ring.

 

Roger Cicala

Lensrentals

March, 2012

19 Responses to “(un)Making Pancakes”

Siegfried said:

Dear Roger,
I could resist it when you recently came with the previous strip tease, but not this time. First of all, I'm glad to hear you can enjoy this kind of fun in your business. Year, I really am. I wish I could do the same and be paid for that!

I'm sorry I don't have answers for your questions you asked, but I can't help giving some other comments:
- I've been told many times by different people, that pancakes miss the peak resolution which more complex lens have got (usually at the center of the frame), but instead they spread the resolution more even across the whole frame. And my experience goes along with this rule. I believe that's an important comment since your phrase "pancakes aren’t generally expected to be razor sharp lenses" may be misunderstood otherwise;
- there may be no real need for precise optical adjustments for those lenses cause of their niche (read: price tag and relative renommee value), optical requirements from further recording device (read: DOF related to sensor size x aperture value) and optical type (as mentioned above, they're more 'flat' and less 'directional' then more complex designs and thus de-centering should not be that much protruded in final output whenever it gonna be 1280 x smth jpg for web or 4000 x smth raw for 13" hard-print).

Oh, boy... I'd better use some wet wipes when reading your next geek-hentai post!

Alles gut,
Zig

tutejszy said:

Fantastic teardown, good reading!
Word about lack of adjustments: In the case of Oly, that one is one of poorest lenses in m43 family. I believe this is the case of Sony lens.

Saran said:

More of the same please! It was a joy to read.
Now let's make those L lenses feel insecure...

Scott said:

The Olympus XA had a 35mm F2.8 with six elements in 5 groups. I wonder if this lens is derived from that one?

I believe the XA used a "retrofocus" design?

Artem K. said:

Great writing, as usual... Can we expect a Sony 16mm pancake in the "For Sale" section or it will be sold under anonymous ID on Ebay? :)

Scott said:

I wonder if the Oly lens is derived form the old XA lens. It was 6 elements in 5 groups I believe. It was a 35mm F2.8 lens. I still have an XA.

Pat Farrell said:

Very cool article.

I'm curious about the motors. Are the part numbers available? Do you think they are generally available though normal distributors? or are they specific to the brands?

LensRentals Employee

Roger Cicala said:

Hi Pat,

Sony doesn't sell parts but every so often you'll see some listed on eBay. If there were model numbers on them, it was too small for me to read without a microscope.

Justin Wan said:

The marks on the Olympus lens looks like Chinese character "伟", a common character used in people names.

Esa Tuunanen said:

Well, isn't the problem more about those "unneeded" left over parts you'll find from desk than putting things back together?

And how about taking apart one those 10+ X superzooms when you have one broken, or otherwise as good as paper weight.
Those should prove lot more interesting inside with all the various moving lens groups.

LensRentals Employee

Roger Cicala said:

Esa,

I'll do a zoom pretty soon, but we'll start with a simpler one. The superzooms are not hard to disassemble and reassemble, but it can be hard to figure out what the various barrels and pieces are doing.

John C said:

Dear Roger,

I love the blog posts that you are writing, and I want to add a few points.

Firstly, the "graffiti" that you see is actually a Chinese "伟" which means good, so I assume it is something written by QC.

Secondly, I own the Sony 16/2.8 and I can tell you that the front makeup ring for the lens is actually screwed in (I've twisted it off a few times because it came loose, and I was interested)

My two cents,
John

Mark Muse said:

One of my favorite lenses is a 45mm Zeiss Tessar f2.8 from the Contax system, which is a manual focus pancake, weighing 90 grams according to Zeiss. I use it on my 5d2 with an adapter. It amazes me that this tiny little thing covers a full frame and does it so well! It is a classic Tessar, four elements, three groups. Stopped to f8 the lens is very sharp, with classic Zeiss contrast, drawing, and color rendering, and virtually no chromatic aberrations worth mentioning. It has huge depth of field, greater than any of my various 35mm Zeiss lenses (ZE f2, CY f2.8, and 35-70 CY @ 35mm). It has some other positive qualities that I can't quite put my finger on.

On the negative side it is so small I have trouble focusing and setting the aperture without having to walk to the front of the camera. It vignettes significantly, but I like that. But it also has some color shift at the extremes (similar to the 21mm ZE but worse) that I end up correcting. Oh, and the mirror hits the lens when focused at infinity, but I use live view all the time.

In many ways it is a pain to use, but it weighs practically nothing and the image quality is superb.

Mark Muse said:

One of my favorite lenses is a 45mm Zeiss Tessar f2.8 from the Contax system, which is a manual focus pancake, weighing 90 grams according to Zeiss. I use it on my 5d2 with an adapter. It amazes me that this tiny little thing covers a full frame and does it so well! It is a classic Tessar, four elements, three groups. Stopped to f8 the lens is very sharp, with classic Zeiss contrast, drawing, and color rendering, and no chromatic aberrations worth mentioning. It has huge depth of field, greater than any of my various 35mm Zeiss lenses (ZE f2, CY f2.8, and 35-70 CY @ 35mm). It has some other positive qualities that I can't quite put my finger on.

On the negative side it is so small I have trouble focusing and setting the aperture without having to walk to the front of the camera. It vignettes significantly, but I like that. But it also has some color shift at the extremes (similar to the 21mm ZE but worse) that I end up correcting. Oh, and the mirror hits the lens when focused at infinity, but I use live view all the time.

In many ways it is a pain to use, but it weighs practically nothing and the image quality is superb.

Yu said:

That's strange should Chinese names be found in there, I though everything NEX is made in Thailand.

Yu said:

Ooooh, my bad, that was the M. Zuiko...

JoeB said:

What kind of glue remover would you suggest to separate the front? I have a broken pancake like this I am going to attempt to repair.

LensRentals Employee

Roger Cicala said:

Joe, we usually just use Isopropyl alcohol. It works faster than regular glue remover and doesn't leave a residue.

ARmand said:

Do you plan to do this on EF 40mm STM Pancake? I don't think nobody is curious about this 'new' stepper motor...

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