Of Course We Took One Apart

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A Look Inside the Canon 16-35 f/4 IS

This is a Geek Article. Many of you don't understand the term 'Geek' properly, so perhaps this will help. As the graph shows, if you aren't both intelligent and obsessed with photo gear, you won't enjoy this article. 

I've tried hard to find whom to credit for this, but haven't been able to. If you know, please let me know so I can credit this brilliant work.

We spent most of the last three weeks doing comparison tests with Canon's new 16-35 f/4 IS. We came away from that comfortable that this is the best wide-angle zoom Canon has ever made. But our day job is fixing broken lenses. I may have mentioned once or maybe three hundred times that trying to keep the 16-35 f/2.8 Mk II lens optically adjusted sucks up our time like a black hole sucks up interstellar dust.

The whole time Aaron and I were testing the new lens, what we really wanted to know was if it was built differently and if adjustments would be either simpler to perform or easier to accomplish, or maybe even both. We weren't sure, though. According to Canon's White Paper, the new lens has some new technology.  The one that made us a little queasy was "newly developed four-group zoom arrangement." When you work on lenses, there are key words you hate. Chief among these is "newly developed," which we usually translate as "nearly developed."

On the other hand, the White Paper also said the redesign involved "matching the design of the EF24-70mm f/4L IS USM, for greater zoom durability and to provide the barrel components with better vibration and shock resistance." That's been a reliable and sturdy lens, so we did have some glimmers of hope.

If you look at the lens diagrams of the 16-35 f/2.8 and the new 16-35 f/4 IS, they're rather similar at first glance.


Lens diagram of Canon 16-35 f/2.8 Mk II (left) and 16-35mm f/4 IS (right)


The Canon White Paper includes a diagram of how the various components move, though, and that made us take notice. Every damn thing inside that lens moves with either zooming or focusing, or both.

From Canon White Paper showing the motion of various elements. Even the aperture is moving.


Needless to say, we were itching to take a look inside one. This is not new behavior for us, though, and management is pretty wise to our ways. So, I wasn't surprised to get a memo that said until we had sufficient backup stock, there was to be no 16-35 f./4 IS disassembly. However, there was no clear definition of "sufficient backup stock," and after some discussion we decided that having one that didn't need to ship for another two hours was sufficient backup stock.

Let's Take Out Some Screws

Those of you working on your lens disassembly merit badges can take out your JIS #00 screwdriver and follow along from home.

Assuming the disassembly position, we take out the 4 bayonet mount screws and the 2 electrical connector screws.

Here's the first mildly pleasant surprise. I'm no big fan of "weather resistance" because it's 80% marketing hype and 20% reality. But the rear bayonet came off only with a bit of a tug, because it has a really thick, soft rubber water weal between it and the rear barrel (red line).

Keeping on with the weather resistant theme, the rear barrel cover, which comes off next, has a nice, deep seal with a rubber gasket (red line) where it mounts into the main barrel. (As an aside, the 16-35 f/4 IS requires a front filter for weather sealing; the front group moves and is not sealed.)

With those parts off, the PCB is exposed and ready to have its flexes disconnected.

I always like the nice, clean way Canon's engineers set up the circuitry on their PCBs.

The zoom/rear barrel assembly comes off next. It's not often you see a picture of screws in a disassembly post, but there's a reason for it. The mount on this lens is held on by 7, count 'em, 7 large screws. The previous record we've seen is 6. I love some over-engineering; it's always a good thing.

In addition to removing the screws, you have to peel up a protective metal cover and remove the zoom key before you can remove the zoom/rear barrel assembly.

After which the assembly slides right off.

If you notice, the zoom ring has a ridged pattern, which is something we've not seen before. If you didn't notice, well, here's a closer view.

I think this may solve two problems we've seen on some recent Canon lens releases, like the 24-70 f/2.8 Mk II. First, it should help the zoom rubber stay in place (stretching zoom rubber is a minor problem on that lens).  Second, it should strengthen the actual zoom barrel. On several recent lenses the barrel has been made so thin that a dent in it will freeze, or at least really stiffen, the zoom ring. This barrel feels a lot stiffer than some previous lenses, which we could easily bend by just squeezing too hard.

The rest of the lens contains all of the optics, the USM system, and the front barrel. It's not quite as modular as the 24-70 f/2.8 Mk II or 24-70 f/4 IS, where the USM assembly is a separate piece, but it's more modular than the 16-35 f/2.8 or 17-40 f/4.

While we're here, though, let's take a close-up look at that large white adjusting collar you can sort of see near the top of the above picture.

There are several points to make. First, this is a thick, robust collar, similar to what we've seen in the 24-70 f/4 IS. Second, the rear group is adjusted with these three collars spaced every 120 degrees. Adjustable collars are nice and precise.  In the 16-35 f/2.8 lens there are no adjustable collars; to center the rear element you loosen three screws and slide it into position by hand, then tighten the screws back down. (see Appendix)

Next we turned our attention to the front, where Canon had a couple of surprises for us. As with most Canon lenses, the name ring peels right off. But underneath the name ring is a second plastic ring. We assumed that would pop off, and ignored the little slots cut in it (red arrow).

Turns out the slots are there for a purpose. The ring doesn't pop off, as Aaron is ably demonstrating in the above image. Rather, it turns 45 degrees and comes right off because instead of little plastic pop-in pegs (which break a lot), it has a full bayonet-like mount, which holds it very snugly around the front element. It also has a thick rubber foam gasket (red line). It can't be quite weather proof because the front element slides up and down within the barrel (the reason this lens needs a filter to be weather sealed), but it certainly must help.

With the second makeup ring off, we can see that, again, Canon has used some robust screws to lock the front element in place.

What you can't see is that the screws holding the front barrel (or filter barrel if you prefer that term) are tucked way down inside.

After which the front barrel comes right off. Notice how obvious the "asphericness" of the front element is. (Yes, I did make that word up. The nice thing about making up words is I don't misspell them.)

Now that the front barrel is off, we can see the front optical adjustment assembly.  The screw collar on the left is not adjustable, but there are adjustable concentrics at the other two locations at that element, allowing some tilt of that element also. There's still a ramp, so rotation of the front element is used to correct spacing. This is definitely an improvement from the 16-35 f/2.8 (see Appendix). Here we have separate brass concentric collars and screws to adjust with. In the older lens there are plastic adjustment collars on a ramp. After they're adjusted the slot is filled with silicone glue.

We decided not to disassemble the USM because we could see all of the remaining helicoid collars without doing so. All were robust and most were brass.

Now that I've seen the insides I'm very optimistic that this lens will be less likely to deteriorate optically over time, and will be more easily corrected when it does. We won't know for sure until we've got a year's experience with it, of course, but from a design and assembly standpoint it looks really, really good.

I know I'm beginning to sound like a Fanboy, especially considering I hardly ever mount a wide-angle zoom on my camera. But I guess the corny old line from the Most Interesting Man in the World works. "I don't often shoot Canon wide angle zooms, but when I do, I prefer the 16-35 f/4 IS."

Roger Cicala and Aaron Closz


July, 2014

Appendix: The Adjustments in the Canon 16-35 f/2.8 mk II

The two questions I get asked constantly about the new 16-35 f/4 IS lens are basically variations on a theme. Will the 16-35 f/4 IS be more likely to stay in good optical adjustment, or be easier to correct if it gets out of adjustment, than the 16-35 f/2.8. So I thought it would be worth showing you the optical adjustment areas on a disassembled 16-35 f/2.8 so you can make the same comparison I'm making.

FIrst, there are three screws like this that hold a round clamp over the rear group. When they are loosened you can slide the rear group around to adjust it's centering.

The front element has three adjustable collars. These set tilt, and then rotate along a ramp to space the front element. Once it's in place the slots are filled with silicone gel that hardens locking them in place. Which is great until you need to adjust them (although it's rarely necessary).

Fionally, way down deep in the lens under the USM motor are a couple of other concentric screws that can be adjusted. Way down deep pretty much means disassemble the entire lens, make your best guess at adjusting them, then reassemble and see how you did. Repeat.

Hopefully this gives you some idea of why we love seeing those big, brass, accessible adjusting screws in the new version. Of course, you aren't going to ever make optical adjustments, but somebody might be doing it for you some day. He or she will be a person who, 15 times during that adjustment process will decide if things are good enough, or if they could be a bit better. I'm all for everything that makes that more straightforward and simpler.

34 Responses to “Of Course We Took One Apart”

Aaron said:

Darn you, you made me indulge my obsessiveness. I traced that Venn diagram:

https://digg.com/comedy/Nerd_Venn_Diagram - which currently is broken/404 :(

Through an alternate direction on Google Image search, I turned up http://freedastyle.blogspot.com/2012/09/nerd.html

Also, lending credence to freedastyle being the author of the exact image you used (even if not the originator of the original Venn diagram), the md5sum of both files (from the blog, and your image) are exactly the same, which is extremely difficult to do if the files aren't exactly the same, bit for bit.

LensRentals Employee

Roger Cicala said:

Thank you, Chuck. There wen't two hours of my day :-) Awesome stuff. i can't believe I'd never heard of him before.

asad said:

FYI, I think the word you were looking for is "asphericity".

Bozilla said:

Those new ribbed focus/zoom rings, are they metal or plastic? If they are metal it seems they are damn hard to manufacture. Also are there no adjustable elements in the mid-barrel elements?

Lynn Allan said:

Well, did the lens ship on time, without the box rattling? Any left over screws?

You could have semi-conformed to the "no [unnecessary] disassembly" mandate by claiming that it might have been dropped, so it needed to be checked for asphericness [sic]?

Or noticed that the oscillating conifilator was just out of spec?

But ... that could get the offender shipped to LR, Canada, which I understand is having issues. Never seen again?

BTW: no obvious need for technical proofreading ... keep up the good work!

LensRentals Employee

Roger Cicala said:

Bozilla, they're polycarbonate (rigid plastic).

LensRentals Employee

Roger Cicala said:

Lynn, shipped on time working fine and no screws left over.

LensRentals Employee

Roger Cicala said:

Asad, probably so. But I wasn't sure how to spell it. So, I went with the made up word :-)

"Never trust a man who always spells a word the same way." Mark Twain

Aaron said:

@Kyle H
I think that reddit thread is the original of the look, but I think my last link is image that Roger used. md5sum confirms that the one from the reddit thread is a different (smaller filesize, different gradients) file. But, the reddit thread is dated much earlier.

Ayoh said:

Hi Roger,

I am curious if lensrentals has ever adjusted/disassembled any Pentax lenses, in particular zooms? I recently bought a 16-50mm 2.8 Pentax lens and am disappointed with the rigidity of the front barrel when zoomed out; the front can be moved laterally a few mm. This cannot be good for the lens performance as I doubt the optical design accommodates such a large tolerance around the alignment of the front element.
The reason seems to be that the extending barrel design is based around 3 linear sliders in which a square sectioned tab slides in a mating slot. This seems like a bad design as there are no provisions for adjustment of the clearance of the sliders and accommodating any manufacturing variation.

I noticed a similarly loose barrel design on a Pentax 18-135mm lens, again with a similar slider design.

Coincidentally both lenses seem to have have conflicting reviews - some good, some bad.

I was curious if you have had any opportunity to work with some Pentax zoom lenses and have any insights into their adjustability/reliability. Thanks!

LensRentals Employee

Roger Cicala said:

Hi Ayoh,

Pentax is an area we haven't ventured into at all. We've opened some up and looked around, but haven't done any optical adjustments at all. They're internally rather different than most of the others and we just haven't gotten our comfort level up to do anything with them yet.

Ayoh said:

Thanks Roger. I will be curious to know any impressions about Pentax if you ever do venture further.

On a related matter, I wonder if you have any comment regarding the durability of mirror-less camera lenses as they seem to be entirely reliant on powered actuation for aperture, focus, and even zooming in some cases. For instance the Olympus 12-40mm f2.8 lens requires the AF group to shift position while zooming and this can only be done under power. In this lens all aspects of operation require powered actuation (aperture, focus and to an extent zooming).

This is fine as it probably relaxes certain design constraints, but the lens becomes essentially unusable without power and propriety control algorithms. As such reliability of the actuation system is critical. With most SLR lenses you can at least focus without power (canon) or focus and change the aperture (nikon and pentax) so if a lens malfunctions in the field you can still take photos (or use the lens on a different mounts without power). I don't think mirror-less lenses will have the same relatively timeless value as older lens designs - they are more designed like short-life electronics rather than long-life instruments.

Vince said:

Hi Roger,

Another great article. I just purchased this lens and did not realize that the weather sealing required a filter. I've used my f/2.8 II in pouring rain without a filter with no issue. That lead me to two questions:

1). Is the f/2.8 II the same way, or is the front weather sealed without filter?
2). Does Roger have a recommendation on a front filter I should use for my new lens? I almost never use filters (other than CPL, NDs.)


Mike said:

Dear Roger, have you taken a Canon 85L2 apart before? If you have, based on the lens internal design, do you see any difficulty for Canon to weatherproof and dustproof the lens? I am wondering if there is any technical reason why Canon has not done so. Thanks a lot for your comments!

Carl Stammerjohn said:

Why are screws which appear to be eccentric called concentric screws? Or am I missing something?

LensRentals Employee

Roger Cicala said:

Carl, because my mind is fading and I misused the term throughout the article.

LensRentals Employee

Roger Cicala said:

Mike, we take them apart all the time. It's a very different lens with an older design (really not much changed from version 1 except a better motor) packed with electronics circuitry. It will take a complete redesign to make those changes.

LensRentals Employee

Roger Cicala said:

Vince, the f2/.8 II is the same design. I don't particularly recommend a brand of filter, but any high end, low profile (thin) filter should do well. B+W, Heliopan, etc. all are good quality at the top end.

LensRentals Employee

Roger Cicala said:

Ayoh, I completely agree. And while I don't have the disassembly expertise with them I do with SLR lenses, it makes optically adjusting a real pain. It must be done on-camera.

Mike said:

Hi Roger, the 85L2 was released in 2006. Were there any weatherproof L lenses released before 2006? If there were, then Canon "could have" weatherproofed the 85L2 as well, but they did not. This points to what you mentioned about the "design issues" in implementing a weatherproof design in 85L2. Is it possibly due to the "air pumping" nature of the front element? Thanks for your valuable insights!

LensRentals Employee

Roger Cicala said:

Mike, I agree with what you said. Air pumping, though, isn't anything to do with it. The lens has very little lnternal movement with focusing, far less than most.

ed in nj said:

I love that you do this, because it satisfies my geek urges enough that I don't have to buy crappy used lenses to take apart for kicks. (Just because I don't have to, doesn't mean I don't...)

Hal Knowles said:

Thanks Roger and Aaron!

As a recent first time customer of Lens Rentals for equipment to support a documentary film about my extended family in honor of my uncle's 80th birthday, all I can say is WOW...your company ROCKS! The quality of the equipment and the personal service is first rate and I look forward to future opportunities to rent from you!

I also really love the always fun, always informative posts on your blog. I'm curious if you can offer any advice on brands and/or online stores were photo enthusiasts can purchase JIS (or other camera lens specific) screwdrivers and related repair tools? As a Micro Four Thirds user, I've got a growing catalog of Minolta MC/MD and Nikon F glass and I'd love to be better positioned to clean, adjust, and repair them as necessary.

Maybe you could do a general post offering some basic (non lens specific) pointers on the tools and workflow for lens repair?


Bill Wallace said:

Thanks for the posts!

A first time reader, I enjoyed your comments concerning Canon lenses. Your comments on Canons 16-35 f/4 lens was interesting and got me thinking about purchasing the lens to replace or supplement my old series one f/2.8. However, like many, I don't use wide focal lengths very often because I'm a birder using Canon's 500 - 600mm lenses. Again, thanks for the information.

Yan said:

How is the ZOOM rotation feel in 16-35mm IS? The new 24-70mm II is very tight and kind of hard to zoom smoothly for Video. It is just too jittery compared to 24-105mm L.

LensRentals Employee

Roger Cicala said:

Yan, it's not jittery, but it is certainly snug. On the other hand, most 24-70s aren't jittery until they get a dent in the very thin metal cover of the zoom ring. Unfortunately, some follow focuses torque down enough on them to dent the ring.

yan said:

Thanks. The 24-70 ii is very snug compared to 24-105. I can zoom smoothly from end to end but hard to do it slowly and almost impossible to make smooth slow zooming in my new lens. It is brand new.

Jason said:

Re the venn diagram

Since we're reading a highly technical blog dedicated to the minutiae of photographic equipment, I guess we're nerds, dweebs, or dorks.

Just kidding, nerds.

James Barber said:

Hi. Did not see the location of the clock battery in the new 7d mkii. Is it user replaceable.


Goran said:

Well done! Canon really had to nail this one, and I guess they did. It will replace my Tokina UWA-zoom. Have you ever opened/adjusted a Tokina AT-X Pro 16-28/2.8 FX? As far as I can tell my copy has minor decentering. It shows up as vertical edge softness on the left side in photos that are focused at (or close to) infinity. In some shots it looks like the focal plane is slightly tilted diagonally from near-left to far-right. Honestly it is hardly noticeable but still annoying and a big reason this lens has not earned my trust. Any thoughts?

LensRentals Employee

Roger Cicala said:

Goran, focal plane tilts in ultra wide angles are very, very common.

Goran said:

I see. Then I'm being way too fussy about this. The Tokina produces beautiful and distorsion-free images. I might keep it but I'm still going for the Canon because I'm a landscape shooter at heart, often framing the sun and lots of water. The flares from the Tokina have caused me a lot of headaches. The lens is heavy too and I don't really need the larger aperture. IS will be invaluable to me, often shooting non-moving subjects in low-light without a tripod, and the conventional 77mm filter ring matches my other zooms (and expensive filters).

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