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First Look: Rokinon 24mm f/3.5 Tilt-Shift – Part 2.

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When we optically tested the RokiBowYang tilt shift, I mentioned that my recommendation was tempered by wanting to see how it was built. Parts and repairs, at least in the U. S., are nonexistent and the price is a bit high for me to consider it a disposable, like the 14mm RokiBowYang. So first thing this morning, instead of doing the work we were supposed to be doing, Aaron and I dove into one.

The Levers

My first concern was the plastic levers that are pushed to rotate the base and planes of tilt and shift. By the way – the forward lever isn’t broken – its base is built at an angle to keep it away from the shift rotation knob. Well done, Samyang engineer.

I removed the screws and plates over the levers, of course but I can’t get a decent photo inside. It’s dark in there. The plastic tabs slip over a metal tab that does the actual work inside. It’s effective and tight right now when the lenses are new. I honestly expect this will be a problem area as the lens gets used.

It would be no big deal if you could buy the plastic part; anyone could change it in about 30 seconds. But RokiBowYang parts aren’t available. If anyone from Rokinon reads this, here’s the one thing you could do to increase the popularity of this lens long-term. Sell the plastic parts. You don’t have to open up a parts department: just put all the plastic knobs and levers in a plastic baggie, call it a ‘refurb kit’ and sell it at B&H.

Opening up the Base

We’ll start by removing the 4 screws that hold the shift mechanism to the tilt mechanism. I should mention that the lens is made out of very high grade plastic that is quite thick and solid.  I have no reservations about these parts. It’s similar to the material the new Canon 24-70 f/2.8 II lens is made of.

The shift plate comes right off. . . .

. . . from the tilt mechanism and optics. A couple of points in this area. The gears themselves are solid brass as you can see above, but the tracks they run in are plastic.

The same goes for the shift assembly in the lower section.

Most other tilt-shifts have brass tracks and gears. That being said, it’s not necessarily a bad thing. The Canon 70-200 f/2.8 IS lenses (including the IS II) have brass gears running on nylon tracks for the zoom ring. But, we do have to replace those every so often because a nylon tooth gets torn off. I will say these are nice, thick plastic teeth, though, so hopefully they’ll hold up well.

Also note the focus key (forked aluminum piece at 3 o’clock in the picture of the optics and shift mechanism, above). We had 3 of 8 lenses that made a scraping sound and sensation when focusing and it’s from the key, which is a piece of stamped aluminum with rather rough edges (see below). Not a big deal, I mention it mostly to let you know not to worry if yours scrapes a bit when focusing. It probably will go away as the rough edges wear off with use.

Back to work. A few more screws and the tilt mechanism comes off.

After which the aperture ring slides off. You can now see the rear optical assembly. It’s a single piece basically, with the elements held in place with glue and retaining rings. It moves as a group when focusing.

Opening Up the Front

Moving around to the front of the lens the makeup ring removes by unscrewing.

Three more screws remove the filter ring.

Showing the 4 screws that hold the retaining ring over the front group.

With these removed the front group comes out as a unit.

Like the rear group, the front group does not have any adjustable elements, simply shims between elements. This group is fixed, not moving along a helicoid track.

A spanner wrench would allow us to open the group and replace the front element, but since there are no adjustable elements inside we didn’t open it up further.

Inside the empty front barrel we can now see the 3 screws that hold the rear group in place. Again, since it’s a sealed group with no adjustments, we didn’t see any need to mess with it.

From the side you can barely see the single helicoid that focuses using the entire rear group.

Conclusions

The original purpose of this disassembly was to try to get an idea about reliability of this lens. I’m left with only the single concern I had when I first examined the lens; I’m afraid the rotation-locking levers might break. That would be absolutely no big deal if the parts were available to repair it. Anyone could do it at home in 30 seconds. Without parts, though, a broken lever means you won’t be able to rotate the planes of tilt and shift.

I have very mild concern about the plastic gear rails for the tilt and shift mechanism, but it seems sturdy plastic and I’m pretty hopeful they’ll hold up well.

Otherwise the lens is really quite well made. Yes, there’s lots of plastic, but it’s very high-quality, heavy plastic with long, thickly-threaded screws holding things together. I have no concerns about the lens from a materials standpoint.

I came away with a lot of admiration for the Samyang engineers who designed this thing, and perhaps some understanding about why the lens is what it is. The design is simple, modular, and logical. That is, I expect, why the lens can be produced with high-grade materials for such an aggressive price. The disassembly took about 15 minutes, tops. Obviously assembly at the factory is going to be quick and staightforward, too.

That being said, the modular design of the two lens groups (front and rear) are a huge cost savings. There are no tilting or centering elements to adjust during the assembly process.

<begin speculation> That may (and I’m completely speculating now) also be why the resolution isn’t quite what the Canon or Nikon lenses have wide open. When designing a lens, the designer has to take into account how much variation to allow. With certain designs a given element might have to be within 0.01mm of a proper spacing distance or 0.01 degrees of tilt off the axis (I’m pulling numbers out of the air for an example) or the lens will be decentered. A more forgiving design might allow 4 or 5 times the margin of error, but in exchange allows more aberration or has a lower resolution.

It seems logical that such a compromise had to be made in the Samyang lens to allow such efficiency of assembly. The designer probably took into account that many people shoot with this type of lens stopped down, where the aberrations are minimized and the resolution very good, and decided that compromise was worthwhile to allow the lens price to be kept so reasonable. </end speculation>

Aaron Closz and Roger Cicala

All images copyright Roger Cicala, 2013 and may not be reproduced without permission.

All hands in images courtesy of Aaron Closz.

Lensrentals.com

May, 2013

27 Responses to “First Look: Rokinon 24mm f/3.5 Tilt-Shift – Part 2.”

Tom Alicoate said:

Interesting lens. Thanks for the tear-down. Lets you really see what you are getting. I love the tilt shifts for their dreamy selective focus. Seems like this lens would be a cost-effective lens for that type of shooting where resolution isn’t king.

Tom

Mike said:

I imagine someone with CAD software and a 3d printer could design a replacement lever without much trouble and post the design somewhere like Thingiverse.

CarVac said:

Are the plastic parts in question too small to be reproduced with 3D printing? Sounds like the sort of thing you could print up a whole bunch of easily.

bn said:

Awesome teardown. I would love to see a similar teardown with the Canon 24 TS-E and/or Canon 17 TS-E.

Samuel H said:

^ My first thought after reading the article. There’s a market here for somebody with a 3D printer and great modeling skills. Expect it to be overcrowded in 2 years.

Steven said:

And here I thought I was being clever thinking of using a 3D printer to make replacement parts. I need to start waking up earlier apparently.

Ben G said:

Very interesting teardown Roger, I second BN’s comments above it would be great to see inside the new version Canon TSE lenses by way of comparison. Just how much more do you get for all that extra cash?

Paul W said:

The modular, compartmentalized aspect is very interesting. Does this mean though that any decentering is caused by non-perfect sitting of the front and back element groups and would be user adjustable? Or is it that certain lenses inside each module was left uncentered?

Aaron said:

Wow, Aaron Closz is such an amazing hand model. Great job! And no, I’m not him, just another Aaron for this great big world we call home.

Hmm…this is still quite a tempting lens for me if it comes down in price a bit in a few months. I think I’ll be fine just knowing that I need to stop it down a good bit.

LensRentals Employee

Roger Cicala said:

Paul, almost certainly not user adjustable. It would be within the sealed groups.

Tony said:

3D printing would not be the best way to go for a 3rd-party replacement parts kit. They would very likely be weaker than the OEM plastic. 3D printing is a close relative to hot-melt gluing.

This is actually a Kickstarter opportunity for someone to replicate the parts in metal.

PeterK said:

Tony > There are many materials that you can print with. And the technology is evolving super fast. 3D printing is the IDEAL way for a 3rd-party replacement parts production.

Markus said:

Hi Roger, thank you for the teardown!
I see glue on some of the screw heads, are all screws tight?
On my Samynang 14 internals screws become loose after a while.
I suppose screws in plastic need glue, cause they can not be as tight as in metal.

Second thing I wonder about: Did you made these scratches on the metal ring of the shift assembly (material test?)

Samuel H said:

Indeed. A 3D-printed ABS piece would work great for this. Not better than the original part, probably, but just as well.

LensRentals Employee

Roger Cicala said:

hi Markus,

They were nice and tight. That’s just Loctite and most lenses have loctite around the screws. Some of them even have silicone caulk.
Roger

Elmer said:

Hi. I’m very curious how the elements of a tilt-shift lens move during tilt and shift (and perhaps during focus). Do they tilt during either movements to bend the light properly? (As I’d expect all elements to be parallel to each other for a normal lens or at 0 degree tilt or shift).

It would be great if you can do an article on this. Thanks!

Andreas said:

Very interesting, thanks Roger!
btw, the RokiBowYang’s are called “Walimex” in Germany, you can add this to the list… ;)

LensRentals Employee

Roger Cicala said:

Andreas, should we go with RokiBowYaWal?

Elmer said:

Here in the Philippines, some of them are distributed under “Polar” brand name. My 8mm fisheye is branded that way.

hendrik said:

Thanks for the inside view. my 2ct are the following:

The combination of plastic and brass for gear is quite usual and not a “cheap” solution primarely, this combination gives good lubrication where no oil is allowed. The geer looks more solid than the one of my canon 17 TS.

to the bargain price:

Maybe there is quite a lot of deveopement costs for small batches of this lens because this is a not very common spezialised lens, but 3x the price of the 14mm is a lot. Manufaturing costs is nearly nothing for all the metal and plastic parts, nor is Assembly in Asia. There seam to be not so many Glass elements than inside the 14mm, so i am quite sure this lens hast potential for big price drops in near future.

CarVac said:

hendrik:

Making the curved dovetail for the tilt joint is no simple task. That’s probably a fairly large portion of the cost of the lens.

Kevin Purcell said:

“[3D printed parts] would very likely be weaker than the OEM plastic.”

It al; depends what you are printing with in e.g. printing in nylon (which you can do with a laser sintering printer) would be perfect for this job.

Not everyone prints with “sugar” these days :-)

Peter Kelly said:

You are the second mention I’ve seen stating the small levers for rotation are plastic, but the Samyang version I have sitting in front of me most definitely has metal levers.

They may look like plastic at first glance (perhaps a plastic coating?) but, if you scratch them, shiny metal shows through.

Perhaps you can test them on your example just to verify, but mine are very strong metal.

LensRentals Employee

Roger Cicala said:

Peter, we took the plastic sleeve off of them, glued onto an inner metal lever. Perhaps they’ve changed since the initial batch.

Peter Kelly said:

Thanks for checking Roger.

You may well be correct but, whatever the reason, I’m happy that they used painted metal parts for the one I have!

It would be interesting if someone could check with Samyang directly as to the explanation.

Haidar said:

thanks Roger for the teardown,
the 5th picture from the top give me an explanation for what is the hanging part in my Samyang
some kind of thin rubber or elastic paper like “[” symbol which we can see at 5th picture was half fallen off, but it still stick in there with just one arm I think.
how the “[” rubber part stick in there, with some kind of glue or what?
I’ll bring it back to the store I bought for reparation this month.

Sorry for my bad english

David said:

Do the Nikon and Canon tilt shift lens use a worm and rack or worm and roller rather than the rack and pinion in the pictures?

One complaint in the reviews is that the unit slips out of position when unlocked. Nothing stops a rack under load (gravity in this case) from spinning the pinion. However, a rack or gear can’t spin a worm gear.

Thanks for the review,

David

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