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Assumptions, Expectations, and Plastic Mounts
  
 
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p.1 #1 · Assumptions, Expectations, and Plastic Mounts


Assumptions, Expectations, and Plastic Mounts
Roger Cicala and Aaron Closz at LensRentals.com posted a great article on mount reliability.
Many lenses like the Canon EF 35mm f/1.4L and EF 14mm f/2.8L Mk II have internal plastic mounts but are considered "Professional Grade". Does it make a difference?

Here is an excerpt to the article:
"The pictures show that for many years lots of very large, very high-quality, professional-grade lenses have had plastic internal mounts. Guess what? They didn’t all self destruct. In fact several of them are widely considered particularly rugged. Looking at 7 years worth of data involving around 20,000 lenses I can’t find any suggestion that plastic mount lenses, in general, fail more than metal mount lenses. Sure, there are certain lenses that fail more than others, but not because they have a plastic mount."

Read full article



Jan 04, 2014 at 07:43 PM
kezeka
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p.1 #2 · Assumptions, Expectations, and Plastic Mounts


Interesting. Having just had to send in a 21/2.8 for a destabalized front assembly with an estimated repair cost of $4-600, it is certainly apparent why a plastic mounting bracket might be preferable in terms of repair cost since it is less likely to throw the entire lens out of alignment when it simply breaks instead of bending and disturbing the rest of the lens.

I have always figured that if assault rifles and cars that see a significantly higher amount of energy can use plastics then there is no reason to distrust them in cameras. That said, I am a firm believer that polycarbonate gears are bad news since they wear down so much faster than metal gearing (in my experience).



Jan 04, 2014 at 08:01 PM
MazeRunner
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p.1 #3 · Assumptions, Expectations, and Plastic Mounts


Well from a design standpoint (cheaper cost aside), plastic does offer certain advantages over metal in some cases:
- Easier to mold into complex parts, since manufacturers can use molds
- Can dampen the vibration from DSLR shutter and/or lens VR (each would have less of an effect on the image)
- Doesn't corrode, more resistant to elements
- Thermostatically and acoustically insulating (the latter might matter if you happen to catch yourself doing video without an external mic)
- Lighter weight

With that said, I do think that nearly all teles or heavier lenses should have a metal mount (anything 2+ lbs., in my opinion).

But the article does bring up a good thing about the weather-sealing: it's not weatherproof! I think I read somewhere late last year from LensRental about photographers who rented lenses and used them during the Holi festival... getting a ton of colored powder into supposedly weather-sealed lenses. ^^



Jan 04, 2014 at 10:27 PM
kodakeos
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p.1 #4 · Assumptions, Expectations, and Plastic Mounts


These arnt Dustin Hoffmans 'Plastics'.

The plastics of today are almost better than metal in many ways.



Jan 04, 2014 at 10:38 PM
Jeffrey
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p.1 #5 · Assumptions, Expectations, and Plastic Mounts


"I am a firm believer that polycarbonate gears are bad news since they wear down so much faster than metal gearing.

A blanket statement like that can not be made. There are over 50,000 types of plastics manufactured for all kinds of reasons. I manufacture precision parts from plastics (machining, not molding) and pay from about $2 to nearly $800 per pound for a variety of engineering grade plastic materials. And the number of applications for plastic gears in nearly infinite, and in numerous environments plastic gears are just fine, and more applicable and cost effective than metal (which I machine a heck of a lot, too).

Lens mounts can be a combination of metal and plastic components. If it is engineered properly with regard to material selection, I have no problem with that.




Jan 05, 2014 at 12:25 AM
sb in ak
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p.1 #6 · Assumptions, Expectations, and Plastic Mounts


When I first saw this blog post, I thought it was more about the actual lens mount (ie, the part that actually seats on the camera.) As it turns out, it looks like even lenses that have metal mounts sometimes screw into plastic. I had no idea, though it turns out this isn't necessarily bad. Thanks for the good read.


Jan 05, 2014 at 12:30 AM
Access
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p.1 #7 · Assumptions, Expectations, and Plastic Mounts


Plastics are very varied in properties, thermoplastics, epoxies, etc. Also there is a class of hybrid materials that are part plastic and part other, ie. FR-4 or a type of fiberglass widely used in circuit boards and some other applications.

Some are good and some not, just depends on what you want it for, and how much you are willing to pay. Not all plastic is bad, plastic just has a reputation for being cheap and low quality (sometimes it is). Metal can be bad too, ie. a lot of the chinese steel produced during the "great leap forward" was quite awful in quality.



Jan 05, 2014 at 02:47 AM
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p.1 #8 · Assumptions, Expectations, and Plastic Mounts


I've long thought that the instinctive objection to the use of plastic was more about perception than reality. Partly it dates to a time when things made of plastic weren't very reliable, but today metal is not always the best material from which to construct things, and plastics and other materials can be more durable.

Dan



Jan 05, 2014 at 04:12 AM
Tom_W
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p.1 #9 · Assumptions, Expectations, and Plastic Mounts


I think that his definition of "plastic mount" might be different from mine. I've only seen 2 lenses with a plastic mount, the 50/1.8 II and one version of the 18-55 IS lens. I think that the plastic bayonet portion of the mount is prone to wear, and isn't a good idea especially with lenses that have any weight. There might be different plastics that have better wear characteristics, but the bayonet mounting surface needs to retain precision for lens alignment purposes.

Plastic in non-wearing areas is a given, and it is reasonably strong. Plus, it can be shaped/formed to create a "break point" whereby the weak spot in a lens structure can be designed into the lens so that repair can be cheaper.



Jan 05, 2014 at 04:33 AM
 

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Vancouver47
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p.1 #10 · Assumptions, Expectations, and Plastic Mounts


It is always a pleasure to read Roger's articles. He is fast becoming the most balanced and credible lens evaluation source on the web. And why not, few if any test more than a few of any lens before commenting. Rogers has a huge database and renter's experiences to form his evaluations and conclusions.


Jan 05, 2014 at 06:01 PM
gdanmitchell
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p.1 #11 · Assumptions, Expectations, and Plastic Mounts


Vancouver47 wrote:
It is always a pleasure to read Roger's articles. He is fast becoming the most balanced and credible lens evaluation source on the web. And why not, few if any test more than a few of any lens before commenting. Rogers has a huge database and renter's experiences to form his evaluations and conclusions.


+1

He busts quite a few myths!



Jan 05, 2014 at 06:12 PM
leftcoastlefty
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p.1 #12 · Assumptions, Expectations, and Plastic Mounts


Roger uses what I think is a rather unique definition of "mount". "The mount is the internal part of the lens where the bayonet — the metal part that twists into the camera — attaches by several screws". No one I know has ever made a distinction between the "mount" and the "bayonet" before -- they are considered the same thing. Or more specifically, a bayonet is one type of mount. (A screw mount being another type.) If you Google for images of a "lens mount", all you see are a bunch of bayonets.

It doesn't surprise me at all that the metal bayonet occasionally screws into a plastic assembly. Plastic can be quite strong, light and versatile.



Jan 06, 2014 at 06:29 AM
docsmiles17
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p.1 #13 · Assumptions, Expectations, and Plastic Mounts


leftcoastlefty wrote:
Roger uses what I think is a rather unique definition of "mount". "The mount is the internal part of the lens where the bayonet — the metal part that twists into the camera — attaches by several screws". No one I know has ever made a distinction between the "mount" and the "bayonet" before -- they are considered the same thing. Or more specifically, a bayonet is one type of mount. (A screw mount being another type.) If you Google for images of a "lens mount", all you see are a bunch of bayonets.

It doesn't surprise me at all
...Show more

Yes he does…I wonder if this is the way replacement parts are named as his definition is different that what most people think of as "mount". If I had a zeiss lens with a canon mount, I would not be referring to the part under the bayonet, which he terms the mount. Further I would not say my zeiss lens has a canon bayonet…sounds crazy

Anyhoo, an interesting article about use of plastics in 'pro' grade lenses



Jan 06, 2014 at 07:48 AM
Paul Mo
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p.1 #14 · Assumptions, Expectations, and Plastic Mounts


I prefer to say the mount is the part on the camera to which you mount the lens by the bayonet mount, and the part to which Roger prefers to refer to should correctly be referred to as the bayonet mount mount.


Jan 06, 2014 at 10:05 AM
RCicala
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p.1 #15 · Assumptions, Expectations, and Plastic Mounts


Heck, the manufacturers don't agree either.

Depending upon the manufacturer the metal part that screws into the camera is either the bayonet mount, the bayonet, the lens mount, or the camera mount. Calling it the camera mount would have been the worst choice, I think. Since Sony calls it the lens mount, I knew that had to be wrong because they don't know doodly about lenses So I went with bayonet.

The 4 screws that hold the metal thingie on the back of the lens go into the next part which is either the lens mount, mount ring, internal mount, internal barrel, or fixed ring; except for the ones, like the Tamron where it is an integral part of the rear barrel. Since the Olympus-broken-zoom freak out's where calling it the mount, I went with that. (In the Canon 35 f/1.4 it's a fixed ring, which I like because then I can tell Aaron we need to fix the fixed ring.)

In retrospect, I should have gone with Paul's choice. Except someone would say that the bayonet mount mount is a camera.


Of course, the thing on the front of the camera where you put the bayonet mount is metal. But guess what the 4 screws that hold it to the camera go into? Often it's metal . . . Oh my. I think I'm gonna have to write another article.



Jan 06, 2014 at 12:04 PM
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p.1 #16 · Assumptions, Expectations, and Plastic Mounts


I like that this article focuses just on a specific part of a lens, the bayonet mount. It does not say that plastic overall is better for a lens, it just focuses on the mount. This said, I wish there would be more detailed data included in the article - when we talk about statistics, what really means "many hundreds" or "doesn't break often" out of the pool of 20 000 lenses mentioned. It makes the story cleaner to read, but I would like to see the more detailed data about it to get to the summarized message that plastic mounts are as good as metal mounts (which can be true, no doubt here). Would be nice to see a table with listed brand lenses, number of each lens used in the field, and number of those where the mount failed.

Would be also nice to see in the future a failure comparison between an older more metal based lens barrel compared to a newer, only plastic-based lens barrel (for example comparing the old Canon 24-70 lens with the new MkII lens body).



Jan 06, 2014 at 02:41 PM
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p.1 #17 · Assumptions, Expectations, and Plastic Mounts


Another great humorous and myth debunking article from Roger. Thanks for the information. It's particularly valuable because you see more cameras and associated periphery gear than 99.9999% of the people on the planet, and you keep records.

Of course it is truly sad that you aren't a weather-sealed professional! We could believe in you so much more

Robert



Jan 06, 2014 at 08:31 PM
Vancouver47
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p.1 #18 · Assumptions, Expectations, and Plastic Mounts


'Lens mounting plate' seems like a good ID for the thingy that locks onto the camera.


Jan 07, 2014 at 01:22 AM





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