Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
02-07-2009, 07:11 AM   #1
Veteran Member




Join Date: Jun 2008
Location: Flyover America
Posts: 4,475
Composites ("plastics") VS Metal

My wife has a $1600 pair of Zeiss binoculars. They are NOT made out of metal but rather what Zeiss calls composite material.

When I sent in our much older metal Zeiss bins for a good cleaning and alignment after 15 years of hard field use I talked with the tech person about the use by Zeiss of composite materials in their new bins.

If I recall correctly here is what he said:

Composites are better, compared to metal, for the following reasons:
1. Far superior shock resistance
2. Much lighter - has the advantage that if you drop them not only will the bins survive it better because of factor 1 but because they are much less likely to self-destruct because of their lower mass. Of course they are much easier to carry around out in the field too.
3. Better thermal stability - that is lens and prism alignment is maintained better under extremes of temperature than with metal - less contraction and expansion.
4. Better weather sealing. Because composites have slightly more "give" they accept weather seals more perfectly than metal.
5. Composites can be molded and then machined to much more complex shapes with a higher degree of precision than metals.

The only down side, and this surprised me, of good quality composite bodies is that they cost MORE to make, not less, than metal. At least according to the tech person.

There were other factors but I have forgotten them.

Given that it seems to be the conventional wisdom on this forum that the use of composites are a sure sign of inferior quality I have this question:

What evidence either from your own personal experience or from objective data that composites are, in fact, inferior to metal in the construction of photo lens' or camera bodies?

I'm not talking about the use of plastics where it is obviously just used to cut down on production costs at the expense of longevity and function or the inappropriate use of plastics for high stress moving parts. That's a no-brainer. But rather high quality composite materials chosen by reputable manufacturers for their superior qualities over metal where appropriate.


Last edited by wildman; 02-07-2009 at 07:24 AM.
02-07-2009, 08:28 AM   #2
Forum Member




Join Date: Jan 2009
Location: Plainville CT
Photos: Albums
Posts: 82
The question is too broad. All composite means is that more than one material is combined to make a material that's stronger, lighter, more flexible, cheaper etc. There's metal composites, fiberglass composites, plastic composites. Each one is made for specific purposes, and each has positives and negatives. And like anything else some are made well and some are not. It has to be taken on a case by case basis.
02-07-2009, 08:48 AM   #3
Veteran Member




Join Date: Jun 2008
Location: Flyover America
Posts: 4,475
Original Poster
QuoteOriginally posted by jeenyus Quote
The question is too broad.
I agree completely if you will accept the fact that many in the forum use the terms composite or plastic too broadly and indiscriminately when damning a particular lens or camera body for being obviously cheap and inferior simply because it is not made out of metal.

The question is broad because the use of the terms "composite" and "plastic" are also used too broadly and without precision in the forum.

The question is very general out of necessity not choice.

Last edited by wildman; 02-07-2009 at 09:02 AM.
02-07-2009, 09:23 AM   #4
Pentaxian
reeftool's Avatar

Join Date: Dec 2007
Location: Upstate New York
Photos: Gallery | Albums
Posts: 8,467
There are some very high quality plastics out there that are stronger than steel and last forever. As the rep mentioned, they cost more than the metals they replaced. As end users, none of us have any way of telling whether the plastic used in a product is a high quality composite or cheap crap that will crack and fall apart if bumped on a cold day. We have to rely on the word of the manufacturer that a high quality material has been used. There is usually a sub contractor involved also. All of us have probably had the experience of that "guarenteed forever" product that broke and have lumped all plastic in general as cheap junk.
In the end we have to rely on the warranty. Will the company back up their claims? Zeiss has been around a long time and makes quality products. I don't own their 1600$ composite binoculars but if they broke in two while adjusting them on a cold winter day I would expect replacement.
The quality issue also exists for metal alloys also. I am a transport refrigeration mechanic and also do truck and trailer repair and have seen far more failures of cheaply made metal parts that corrode and seize quickly or break than the plastics, especially door handles. I can remember many a cold winter morning when a driver would come into the shop with a door handle in his hand. That rarely happens any more and failures usually involve metal parts inside. When a plastic handle does break, the "cheap plastic" comment comes out. Reality is we don't keep the plastic handles in stock because failures are rare and usually involve driver abuse but we stock 2 each of the metal handles for the trucks that use them because they fail on a regular basis.

02-07-2009, 10:14 AM   #5
Pentaxian




Join Date: Oct 2006
Location: Dayton, OH
Photos: Gallery
Posts: 4,396
Having a Ph.D. in materials engineering, I find some of the generalizations to be not entirely true.

Tim

QuoteOriginally posted by wildman Quote
My wife has a $1600 pair of Zeiss binoculars. They are NOT made out of metal but rather what Zeiss calls composite material.

When I sent in our much older metal Zeiss bins for a good cleaning and alignment after 15 years of hard field use I talked with the tech person about the use by Zeiss of composite materials in their new bins.

If I recall correctly here is what he said:

Composites are better, compared to metal, for the following reasons:
1. Far superior shock resistance

Actually, metal absorbs energy better than plastics. This means that the composite bins will bounce higher and sustain a larger force on the second bounce. Also, being less absorbant, they will tranfer more energy to the glass componets within the bins.

2. Much lighter - has the advantage that if you drop them not only will the bins survive it better because of factor 1 but because they are much less likely to self-destruct because of their lower mass. Of course they are much easier to carry around out in the field too.

Weight is the primary advantage to any plastic item over metal. Again, plastics absorb less energy than plastics and can crack much easier.

3. Better thermal stability - that is lens and prism alignment is maintained better under extremes of temperature than with metal - less contraction and expansion.

I haven't looked at the coeficient of thermal expansion (CTE) for plastics for some time so I'm not going to comment here.

4. Better weather sealing. Because composites have slightly more "give" they accept weather seals more perfectly than metal.
5. Composites can be molded and then machined to much more complex shapes with a higher degree of precision than metals.

Again, weather seal will be more dependant upon CTE than the acceptance of seals themselves (what ever that means).

The only down side, and this surprised me, of good quality composite bodies is that they cost MORE to make, not less, than metal. At least according to the tech person.

Very true. In the automotive industry the cost verse weight savings is always a consideration when switching from metal to glass filled plastic or other composites.

There were other factors but I have forgotten them.

Given that it seems to be the conventional wisdom on this forum that the use of composites are a sure sign of inferior quality I have this question:

What evidence either from your own personal experience or from objective data that composites are, in fact, inferior to metal in the construction of photo lens' or camera bodies?

I'm not talking about the use of plastics where it is obviously just used to cut down on production costs at the expense of longevity and function or the inappropriate use of plastics for high stress moving parts. That's a no-brainer. But rather high quality composite materials chosen by reputable manufacturers for their superior qualities over metal where appropriate.
02-07-2009, 10:36 AM   #6
Otis Memorial Pentaxian
Loyal Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 31,716
I think the main complaint with non-metal construction is that the products often feel cheap to the touch with mechanisms that feel loose, gritty, or imprecise. There is also the fear of brittleness with cold/age and just plain fragility. This last may be a false fear. Drop a Spotmatic with a 200mm Takumar to the ground and it may look just fine except for the all-to-common dent to the top of the pentaprism housing. Drop a K20D with a DA 50-200 and you will expect to see lens innards, maybe camera innards, and possible full loss of body function.

In the above example, is the K20D more fragile than the Spotmatic? Probably not. The damage to the lens and camera is just not as obvious. The metal housings mask internal damage. When I was younger I was cautioned to beware of buying a used camera that had been dropped and shown how to look for the subtle evidence of such.

On the other hand...this is a little off-topic, but pertinent in regards to the metal vs. composites question...I remember about fifteen years ago taking part in a 100km bicycle ride (metric century) in Southern California. I was on a borrowed steel-framed bike and had only completed the first mile or so when I saw the most amazing thing happen ahead of me. I very well-equipped rider on a cutting-edge composite framed bike abruptly "went to ground" and was skidding along the pavement. He was just riding along and his $5000 showpiece decided that it was time to fold and fold it did...into two distinct pieces. Amazing!

There is a saying in cycling circles. "Steel is real..."

Steve

Last edited by stevebrot; 02-07-2009 at 10:54 AM.
02-07-2009, 11:02 AM   #7
Ole
Administrator
Ole's Avatar

Join Date: Sep 2006
Location: Copenhagen, Denmark
Photos: Gallery | Albums
Posts: 4,118
In the end it boils down to the quality of the design, quality of materal used, and quality and tolerances in manufacturing.

The DA*50-135 for example, is made of composite material, is of a very high build quality with tight tolerances. It feels to me just as solid as a metal FA*, and it won't lose paint!

Towards the other end of the scale you have the FA 24-90, also made of composite, but the inner lens barrel is wobbly and not confidence inspiring.

Then there is "plastic", like in the material used for the aperture ring on some A lenses (A 50/1.7 for example). It doesn't age well, it changes form and therefore tend to get stuck or at least become hard to twist.

In the dropped camera and lens department I have experience with survivals in both camps: K1000 with 50/1.4, ME with K 45-125, and K10D with DA 12-24. All three combos survived; the first two being metal got dented, of course; the third just a bit scratched on the lens hood.

The only non-surviver was a point and shoot zoom camera; a major brand, I don't remember which. It didn't survive a fall of just one meter.
02-07-2009, 12:27 PM   #8
Inactive Account




Join Date: Jun 2007
Location: Baltimore, Maryland USA
Posts: 162
As someone that worked for 2.5 years in my youth as an apprentice machinist for a machine shop that specialized in high-precision work, I can tell you unequivocally that most plastics require far more attention to the little details in order to machine them to very tight tolerances, than do most metals....For a while I helped make the carbon-impregnated plastic seals that went on either end of the drive shafts for the General Electric turbine engines being used by the U.S. Army in their attack helicopters..These seals were very complex to make, and the tolerances had to be kept to + or - 0.0002" in all directions..That's two ten thousandths of an inch..They were approximately 2.00" in outside diameter with an internal diameter that was approximately 1.75"..The thickness was approximately thirty thousandths of an inch..They had a full radius on both the I.D. and the O.D.They had to be flat across their entire diameter to the same tolerances as in every other dimension..They were a cast iron pain in the a** to make..Every single aspect of making these things had to be done slowly, and with extreme care..This was in the early 1970's..Nowadays, one would have super high tech CNC machines to perform this kind of work..I had to perform every task on a series of lathes, feeding the tools by hand..I made 5000 of those little bast***s over an 8-month period, being criticized the entire time by the shop foreman, and master machinists..There was a 2-month hiatus..Then the shop foreman came to me and asked me to work on another order for G.E..Seems that of all the shops in the USA tasked with making the seals, our shop had done the best job, and was being offered another contract..I hated those seals!!!..

Bruce

02-07-2009, 12:57 PM   #9
Pentaxian
SpecialK's Avatar

Join Date: Dec 2006
Location: So California
Photos: Gallery
Posts: 15,539
QuoteQuote:
many in the forum use the terms composite or plastic too broadly and indiscriminately when damning a particular lens or camera body for being obviously cheap and inferior simply because it is not made out of metal.
Very true. However, there are few qualifications to be a poster or reviewer, unfortunately. It makes me wonder about the rest of their post.
02-07-2009, 01:15 PM   #10
Damn Brit
Guest




Even if newer plastic (or composite) lenses are superior to metal, they feel different and I think that is the crucial thing. In another generation probably it will be the other way round, if a lens is made of metal it will feel different. It's just what we are conditioned to, at present, plastic is considered to feel cheap.
02-07-2009, 01:37 PM   #11
Veteran Member




Join Date: Jun 2008
Location: Flyover America
Posts: 4,475
Original Poster
"Actually, metal absorbs energy better than plastics. This means that the composite bins will bounce higher and sustain a larger force on the second bounce. Also, being less absorbant, they will tranfer more energy to the glass componets within the bins."

All else being equal if you dropped something to the floor and it did not bounce or bounced very little

or

you dropped something from the floor and it bounced, say, three times.

Wouldn't the internals in the second case possibly survive better because the total energy, which is the same in both cases, be expended over three smaller impacts with no single impact very severe rather than one very large one more or less all at once?

In other words wouldn't you rather have your K20D suspended inside a rubber basketball rather than a steel one? After all a football helmet is made out of "plastic" not metal. I don't know I'm only guessing. Let's call this Wildman's big bang theory of shock absorption.

"Again, plastics absorb less energy than plastics [sic] and can crack much easier."

This seems like an overly unqualified statement...

...do you really mean to say that;

"any plastic absorbs less energy than any metal and any plastic will crack much easier than any metal?

"Again, weather seal will be more dependant upon CTE than the acceptance of seals themselves (what ever that means)."

If memory serves what the tech meant is that composite material it's self, because of it's elasticity (my word not his I'm not sure exactly what word he used) makes a good seal it's self. He pointed out that the O rings for the composite bins is slightly harder stiffer and sized a bit larger than those used on the old metal bins because the composite material, due to it's properties, to some extent forms around the O ring as well as the O ring sealing against the composite material. This gives the new bins a tighter, longer lasting more trouble free seal than can be achieved with the old metal bodied bins.

I hope I explained all this accurately.

Last edited by wildman; 02-07-2009 at 03:24 PM.
02-07-2009, 07:20 PM   #12
Veteran Member
creampuff's Avatar

Join Date: May 2007
Location: Singapore
Photos: Gallery
Posts: 3,955
Polycarbonate plastic for me. I only have to think about my old film SLRs and the little nicks and dents from the many knocks they went through. With plastic, the most that would happen is a crack.

With lenses, polycarbonates are the way to go for faster AF (less inertia so faster start and stop of the focus ring).
02-08-2009, 07:40 AM   #13
Veteran Member




Join Date: Jun 2008
Location: Flyover America
Posts: 4,475
Original Poster
QuoteOriginally posted by reeftool Quote
Will the company back up their claims? Zeiss has been around a long time and makes quality products. I don't own their 1600$ composite binoculars but if they broke in two while adjusting them on a cold winter day I would expect replacement.
And you would probably get a replacement.
When I sent my ancient Zeiss 7x42 BGA in I simply specified a cleaning and collimation check/adjustment.

When I got them back they also had replaced the eyes cups and the armor covering as well - no charge. This was in 2007 and I had bought them in 1990.
02-11-2009, 09:31 AM   #14
Veteran Member
Clicker's Avatar

Join Date: May 2008
Photos: Gallery
Posts: 3,241
I like composites mostly for it's weight vs metals.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
bodies, composites, lens, metal, plastics, quality, tech, weather, zeiss
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Sports "Highside Exit" took 1st Place in DPReview "Missed It by THAT much, Part 1" Challenge MRRiley Post Your Photos! 27 02-21-2010 08:26 PM
K1000 body "ding" - defect, accident, or "feature"? dannywho Pentax Film SLR Discussion 6 10-08-2009 06:11 PM
K20d-Frame Count on panals..works w/"M" & "P" mode only? arbib Pentax DSLR Discussion 1 08-28-2009 05:47 PM
"Hunger for a DA*50-135?" or "The DA*50-135 as a bird lens!" or "Iron age birds?" Douglas_of_Sweden Post Your Photos! 4 08-13-2008 06:09 AM
Anyone bring "E2" fluid or the "Digital Survival Kit" on a plane? m8o Photographic Technique 2 07-31-2007 06:20 PM



All times are GMT -7. The time now is 05:17 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top