October 01, 2014, 12:38:09 AM

Author Topic: Are Metal Mounts Better Than Plastic?  (Read 11524 times)

LetTheRightLensIn

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Re: Are Metal Mounts Better Than Plastic?
« Reply #30 on: January 04, 2014, 04:01:39 PM »
And this is one reason why I don't like how most reviewers evaluate "build quality."  They evaluate the feel of the materials of the parts they can see, which is a mistake.  Think of cheap faucets with nice finishes but plastic gears.  The same thing happens with lenses.  Having a metal outer barrel is not indicative of the materials used for the inner assemblies that often matter more...

OTOH, you seem to have missed the part where the materials for the inner anchors being metal actually might be worse than from plastic.

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Re: Are Metal Mounts Better Than Plastic?
« Reply #30 on: January 04, 2014, 04:01:39 PM »

Dimson

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Re: Are Metal Mounts Better Than Plastic?
« Reply #31 on: January 04, 2014, 04:09:55 PM »
this is probably one of the best and most informative write ups i've read at CR so far. truly a great insight on how the stuff works behind the scenes. i hope there will be more of this kind

TexPhoto

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Re: Are Metal Mounts Better Than Plastic?
« Reply #32 on: January 04, 2014, 04:11:09 PM »
Great article.  I worry about 3 things with my lenses. 
1. fungus. I live in a very humid environment
2. Will the IS element fail?
3. Will he AF element fail?



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Re: Are Metal Mounts Better Than Plastic?
« Reply #33 on: January 04, 2014, 04:18:21 PM »


'Carbon fibre' is in fact a composite; there are carbon fibers in an epoxy resin-type matrix. The Epoxy is a 'plastic' so it is in fact reinforced plastic. The principle is the same as reinforced concrete, where the concrete carries the compression, and the steel the tension.

The devil is in the details. those fibers don't always lineup so that they reinforce the part in the right axis.  It takes a lot of experience with making molds, superb process control, and frequent checking to make sure the fibers are doing any good.  I had a plastic bayonet lens from Canon where the bayonet flanges broke away. 
Canon, like many other companies is out sourcing more and more parts, and having problems as a result. 
 
 

infared

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Re: Are Metal Mounts Better Than Plastic?
« Reply #34 on: January 04, 2014, 04:23:01 PM »
Wouldn't "all metallic construction" be kinda hard to see through? And those all metallic circuit boards would be tricky to engineer.
Obviously there is glass in the lenses, plastic-coated wires, rubber on the focus rings, etc...DUUUUUH...but like Roger says..Zeiss uses metal throughout the Lens. Zeiss could make that claim in their literature..in this instance, it is dishonest for Olympus to make that claim.
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Skulker

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Re: Are Metal Mounts Better Than Plastic?
« Reply #35 on: January 04, 2014, 05:49:37 PM »
Look at the mount on the body, it's metal, but what is it attached to?

Umm, I think you have supplied your own awnser. The Body.  ;D

On my 1Dx that's made of magnesium BTW. But of course its weather sealed and Profesional quality.  ;D

I think your making a perfectly valid point, just couldn't resist the silly reply.
If you debate with a fool onlookers can find it VERY difficult to tell the difference.

Don Haines

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Re: Are Metal Mounts Better Than Plastic?
« Reply #36 on: January 04, 2014, 06:07:23 PM »


'Carbon fibre' is in fact a composite; there are carbon fibers in an epoxy resin-type matrix. The Epoxy is a 'plastic' so it is in fact reinforced plastic. The principle is the same as reinforced concrete, where the concrete carries the compression, and the steel the tension.

The devil is in the details. those fibers don't always lineup so that they reinforce the part in the right axis.  It takes a lot of experience with making molds, superb process control, and frequent checking to make sure the fibers are doing any good.  I had a plastic bayonet lens from Canon where the bayonet flanges broke away. 
Canon, like many other companies is out sourcing more and more parts, and having problems as a result.
The fibers in carbon fiber components are usually from a cloth so alignment is easy.... It's sort of like with fiberglass.you could lay up fiberglass cloth in a mold or you could use  "chop glass", where short fibers were blown in place.... The chop layup is faster and cheaper, but the laid up cloth is both lighter and stronger.

BTW, we use carbon-fibre dishes in aircraft and on the satellites..... They are far better than metal dishes, particularly with thermal stability and weight.
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Re: Are Metal Mounts Better Than Plastic?
« Reply #36 on: January 04, 2014, 06:07:23 PM »

Skulker

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Re: Are Metal Mounts Better Than Plastic?
« Reply #37 on: January 04, 2014, 06:09:50 PM »
I think that most people will mean the bayonets when they refer to "mounts". It may be that Roger knows better. Maybe people complain when the "mounts" break and from Rogers experience it's what he calls the mount that breaks rather than the bayonet.

On the subject of plastic mounts. Be they bayonets or what the bayonet mounts on. Many will be made of a filled  plastic. That filler may be glass, carbon, ceamic or inert filler as there are several options. It can be in the form of fibers, beads or powder as well as the obvious options of woven material that you probably wouldn't expect in a bayonet, but might well find in a mount as defined by Roger.

There are also several options for the matrix as well. Epoxy is not the most likely for this type of application.

The obvious problem with bayonet mounts for lenses is wear. As the lens is mounted and removed it may well be subject to abrasion. If it wears and the filler is exposed it can create a very abrasive paste or dust that may wear even more, and get in the camera. Thus causing even more wear.

Please don't think I don't like plastic, I'd quite happily buy a lens with "plastic" bayonets. But I wouldn't expect to see them on my 200-400 when I get it. (in my dreams)
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Skulker

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Re: Are Metal Mounts Better Than Plastic?
« Reply #38 on: January 04, 2014, 06:19:09 PM »

The fibers in carbon fiber components are usually from a cloth so alignment is easy.... It's sort of like with fiberglass.you could lay up fiberglass cloth in a mold or you could use  "chop glass", where short fibers were blown in place.... The chop layup is faster and cheaper, but the laid up cloth is both lighter and stronger.

BTW, we use carbon-fibre dishes in aircraft and on the satellites..... They are far better than metal dishes, particularly with thermal stability and weight.

You won't find may bits in a mass production lens made that way.


Edited to correct typo.
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WPJ

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Re: Are Metal Mounts Better Than Plastic?
« Reply #39 on: January 04, 2014, 06:56:56 PM »
I previously owned the 24-70 f/2.8L. I could have sworn it had a metal mount. Am I crazy?

nope your thinking of the bayonet part Roger is referring to the internal mount which you cannot see unless you take the bayonet off

zim

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Re: Are Metal Mounts Better Than Plastic?
« Reply #40 on: January 04, 2014, 07:06:10 PM »
Three of the four screws sheared.

Doesn't sound like a plastics issue, interesting that the weakest link would seem to be the screws under a shearing force. You could argue that's good design!

privatebydesign

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Re: Are Metal Mounts Better Than Plastic?
« Reply #41 on: January 04, 2014, 07:48:31 PM »
When I snapped my 16-35 f2.8 in two I was told by a tech at CPS that the plastic cage that the metal mount screwed to was a designed breaking point. He said that if camera and lens were dropped it was supposed to break away before too much impact was transferred to the glass.

My 16-35 was mounted to a 1VHS and fell onto a concrete floor. The four screws snapped tabs off the plastic cage, the mount stayed on the camera, the lens rolled away with no damage to the glass, barrel, or filter threads, all the ribbon cables snapped and it cost $150 to fix. They replaced the plastic cage (they actually offered to sell me one so I could repair it myself as I was in a fairly remote spot), and the ribbon cables, no damage to the glass.

I am very happy with the design, I think it worked as intended and prevented my lens being damaged more severely.
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sagittariansrock

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Re: Are Metal Mounts Better Than Plastic?
« Reply #42 on: January 04, 2014, 08:18:43 PM »
However, for the bayonet 'teeth' of the mount, plastic wears down more easily than metal (vs. the screw-holes, which aren't subjected to routine 'wear'). That means a lens with a plastic mount (as I'd say is the common definition pictured above, not Rogers's use of the term), would be able to tolerate fewer mount/unmount cycles than a lens with metal bayonet teeth. 

While it is true that plastic mounts (our definition, not Roger's) are far easy to break that metal ones, it might be better to have an easily replaceable breaking point in case the camera with the lens mounted falls at a weird angle. In fact, as far as I have seen from images of dropped cameras, the lens mount is what breaks off most often (even including metal ones) and I think that is for a very good reason. The plastic flanges in the 50 II and 18-55 definitely feel dodgy but I suspect they are much stronger than they look. I even feel that the elasticity of the plastic barrels (pun not intended) might be better at absorbing shock inside than the rigid metal barrels. This is engineered plastic, not the same thing cheap toys are made out of.

When I snapped my 16-35 f2.8 in two I was told by a tech at CPS that the plastic cage that the metal mount screwed to was a designed breaking point. He said that if camera and lens were dropped it was supposed to break away before too much impact was transferred to the glass.

+1. Exactly my thoughts.
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Re: Are Metal Mounts Better Than Plastic?
« Reply #42 on: January 04, 2014, 08:18:43 PM »

Random Orbits

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Re: Are Metal Mounts Better Than Plastic?
« Reply #43 on: January 04, 2014, 09:33:55 PM »
And this is one reason why I don't like how most reviewers evaluate "build quality."  They evaluate the feel of the materials of the parts they can see, which is a mistake.  Think of cheap faucets with nice finishes but plastic gears.  The same thing happens with lenses.  Having a metal outer barrel is not indicative of the materials used for the inner assemblies that often matter more...

OTOH, you seem to have missed the part where the materials for the inner anchors being metal actually might be worse than from plastic.

Umm... no.  I said NOTHING about whether or not lenses should be made with metal or plastic.  My point is that you cannot tell build quality by just evaluating just how it feels on the outside.  One can't evaluate quality without understanding the design and the design tradeoffs, and that is impossible by just feeling the outside of a lens.

DanielW

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Re: Are Metal Mounts Better Than Plastic?
« Reply #44 on: January 04, 2014, 09:56:11 PM »
I think Rogers's definition of a plastic vs. a metal mount differs from how most people think about those terms.  For most of us, we're talking about the bayonet parts - the 'teeth' that lock into the mount on the camera. 

 

The EF-S 18-55 on the left has a 'plastic mount', the EF 17-40L on the right has a 'metal mount'.  Very few of us disassemble lenses, so we have no idea what's behind that mount surface.  Roger is talking about how the screws that that attach that visible surface piece to the lens are connected - do those screws go into metal screw-holes that are attached to the frame of the lens, or are the screw-holes plastic?

'Plastic' can be quite strong, so for a 'light' lens (most lenses under 100mm, with the exception of the 'magic cannonball' 85L), I agree with Roger that I wouldn't expect any issues, and 'professional' could apply.  However, for the bayonet 'teeth' of the mount, plastic wears down more easily than metal (vs. the screw-holes, which aren't subjected to routine 'wear'). That means a lens with a plastic mount (as I'd say is the common definition pictured above, not Rogers's use of the term), would be able to tolerate fewer mount/unmount cycles than a lens with metal bayonet teeth.  Since a professional lens would be expected to last years and most 'pros' own several lenses and change them frequently, it makes sense to associate a metal mount (as pictured above, regardless of how it's screwed in) with 'professional' build.

I understand that, and even make the same (in my case unfounded) assumption about the plastic teeth wearing down more quickly, but would not Roger have noticed it so far if it did happen to be true?

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Re: Are Metal Mounts Better Than Plastic?
« Reply #44 on: January 04, 2014, 09:56:11 PM »