In defense of plastic

[blumesan]

In defense of plastic.

I am climbing on my soapbox today with the sole aim of starting a debate on the merits and disadvantages of using modern synthetic materials in the construction of camera bodies and lens barrels. In several threads in this forum (not least in those dealing with the Aria body) the word "plastic" is invariably used as a pejoritive. Most frequently it is associated with the adjectives "cheap", "flimsy" or "inferior". Yet, and this is what puzzels me, I am not aware of a single posting which describes the failiure of a plastic component in a situation where one made of metal would have likely survived.

Let me state right here that I am not an expert on materials or photo equipment construction. Nevertheless common sense tells me that should you drop a camera or a lens, or otherwise subject them to sudden impact, the delicate internal components are much more likely to sustain substantial damage long before any significant damage is done to the housing. This is quite comparable to the situation in which one can sustain severe damage to the brain (concussion) without any significant damage to the container which houses the brain, the skull.

The first camera bodies were made of wood, as were my first pair of skis and my first tennis racket. The next generation of these objects employed metal and eventually modern technology led to the use of synthetics, fiber reinforced plastics, etc. In each case the new materials were employed because they offered real improvements to the functionality of the object and generally at little or no cost to their durability.

I will readily admit that synthetics have replaced metal in the construction of many items simply on the basis of their lower cost and at a significant sacrifice to durability and function. In such cases the epithet "cheap plastic" is well deserved. However, as I suggested above, I am unaware of any evidence that such is the case with mid to high end photographic equipment produced by reputable manufacturers. So I introduce this topic to the forum in order to avail myself and other members of the experiences and opinions which may support or contradict this thesis.

Respectfully,
Mike Blume

 

[pallavidino]

Mike,

You wrote some very reasonable words here which covered pretty well the advantages and disadvantages of plastic but let me point some issues that IMHO needs to be considered for such appraisal.

When the matter is sudden impact due to dropping or hitting your camera let me tell you that metal bodies does a better job. One reason is that they are heavier. There is a physhics law that sais that the heavier bodies take more portion of the impact energy than ligther ones, so all delicate and light components of the camera would be more protected inside a heavy body. Is like a heavy camera hurts more the material hitted and hurts less itself, when drooped

But a light body is more confortable to carry on, mainly when you are out taking pictures for the hole day, so my point have to be balance whith how much dunger are you planing to expose your equipment.

I guess most of issues against plastic bodies comes by the fact that they feel like bending and flexing in your hands, which they do, but in very small amount. Is much more a metter of perception here.

I had an interestin experience trading my Canon 50 and testing its replaicement model, the Canon 30. The last have much more metal parts than my 7 years old camera, but feels more delicate. One good ex&le (the 50) of a plastic body that can feel sturdy with a good enginering project and no too many cost reductions concerns.

Hope that help and hope my English was ease to understand.

Ricardo

 

[afranklin]

Hi Ricardo,

"When the matter is sudden impact due to dropping or hitting your camera let me tell you that metal bodies does a better job. One reason is that they are heavier. There is a physhics law that sais that the heavier bodies take more portion of the impact energy than ligther ones, so all delicate and light components of the camera would be more protected inside a heavy body. Is like a heavy camera hurts more the material hitted and hurts less itself, when drooped"

I don't agree with this. The metal is more rigid, and therefore won't absorb the impact, but tranmit it TO the other components more so than a more resilient/absorbant material would. That is why mechanical d&ening materials are made of, plastic, rubber and other of these types of materials.

Also, the heavier something is, the higher the impact force is...from physics 101, f=ma, force = mass x acceleration, and given the acceleration is equal (gravity), more mass == more force.

Regards,

Austin

 

[pallavidino]

Hi Austin,

Your point is correct but little bit out of my point in this case. My first thoughts were related to the ratio between very light electronics components and very heavy metal or plastic structures. Is a metter of inercia here. The deceleration of internal components will be almost the same in both cases and what uses to damage it is its (components) mass, following the formula you pointed.

Think of my point here like a box on your table with a glass of water inside. Get a hammer and hit this box strong in one side. Now think that instead of a box is an iron safe on top of your table...

Also remember that all fragile components in our camera are dumped from the frame, so the vibrations generated doesn't count much here.

"Is like a heavy camera hurts more the material hitted and hurts less itself, when drooped"

Regards

Ricardo.

 

[noidea]

Ricardo,

Sorry, but I tend to disagree. Just look at your car.
The impact prone parts (front and back) are built rather soft like a cushion. They'll bend in a crash to keep you safe and hopefully unharmed.
Yes, the passenger cell itself is harder, but it won't take much of the impact force anymore.

Volkswagen showed some tests in the 70's what happens to a car passenger during a crash in a rather rigid Beetle compared to a softer Golf. The Golf won outright - and this was in the infancy of crash research.

However, I prefer a metal frame at least around the lens mount - having ruined my plastic Nikon F50 with the use of heavy pro lenses handheld.
But for the rest of the body I don't care much if it is "plastic" or not.

 

[pallavidino]

Claus,

You and Mike are disagreing because you are analizing the physical event for one point of view, which differs from mine. Your concept here is perfectly justified but there are more energy and forces variation in this cenario.

Seems that you are looking at the relationship between the internal components and the body, which in your ex&le would be the car and the passengers. The concept I am defending here is the relation between the group body&components and the material they are hitting (the wall).

Think about 2 cameras (1 RebelX and 1 EOS 1v) falling from your chest heigth to a soft floor. Physhic sais that they reach the floor at the same time at the same velocity. The weight of a heavier system will "dig" more into the ground so the deceleration lenght will be bigger and, consequently, the acceleration value will be smaller causing less stress on internal components. f=m.a

This ex&le is easy to undestand due to the softness of the floor, but can be used with all kinds of material since the rule here is just about mass. Harder material will generate smaller dig holes, but this holes will be even smaller for lighter cameras.

Is good to mention that plastic have a better dumpening caracteristics but it dries less energy when cracking then metal when bending. Also, if they hit someting sharp, metal would deform less due to concentrated pressure than plastic, which will probably beak apart and expose sensisitve internal componentes.

After a dozen of english mistakes, my 2 cents

Ricardo

 

[afranklin]

Ricardo,

"The weight of a heavier system will "dig" more into the ground so the deceleration lenght will be bigger and, consequently, the acceleration value will be smaller causing less stress on internal components. f=m.a"

Without knowing the weights and the deceleration you can't make that claim.

Personally, I think your premise is wrong, as neither will "dig" into cement very far what so ever, and any difference would be insignificant.

Regards,

Austin

 

[noidea]

Well, I normally don't use my cameras as sledgehammers.

See it in that way: Plastic is more prone to break I agree with you on that. But on the other hand I prefer to replace a "cheap" plastic panel over the more expensive replacement of the electronical parts shaken to rubbles by the impact.

And I'm not sure if I should be proud of my full metal jacket Nikon FM2 that it digs a deeper hole than the plastic F90 when I drop them
(still didn't get a Contax, but soon!)

 

[blumesan]

Wonderful.
I was hopeing for a lively discussion.

I disagree with Ricardo's physics. The internal damage will depend on the rate of deceleration at the end of a fall. Perhaps a foam mattress will cause less rapid deceleration, but I doubt if there is much difference between a carpet and a cement floor. The damage to the internal components results not so much from a transfer of the impact to them, rather due to the fact that they keep moving when the body stops. This displacement is very detrimental to delicate electronics and carefully aligned prisms.

Claus's observations are certainly pertinent. However I doubt if either metal or plastic camera bodies provide much of a crush zone effect. But he is certainly on point when he notes that plastic lens mounts will take less punishment from everyday use.

I would really like to hear more of actual users eperience with failures of plastic components.

Thanks to all.

Mike.

 

[noidea]

Mike, I think I can help on that.

My first F50 fell from the open tank bag on a paved parking lot - about 3 ft. Luckily it fell lens first (no, it didn't make a dent in the asphalt!).
The wonderful 35-80 "kit" lens was shattered into pieces (cheap plastic cr*p). The body itself was unharmed.
Though the camera was still working it gave some rattleing noise when you shook it. However I didn't test if AF, exposure and so on where still in calibration (didn't have a clue about that "techno babble" that time).
Back home I sent the camera without comment to Nikon and they replaced it - also without comment - with a refurbished camera under warranty.
This second F50 got killed from the usage of the heavy 35-70/2.8 Nikkor and 80-200/2.8 Tokina.
Those lenses nearly pulled the lensmount out of the body. I still have it though as a backup backup camera, but my daughter only uses it with cheap (and light!) lenses.

My FM2 went down with the tripod once when a client fell over the synch cable (if they have to hold in the jack they don't!!!). Lens dead, camera alive - and still my favourite in the studio.

 

[noidea]

But thinking about it ... I have my eye on an Aria.

Don't scare me about the plastic!

 

[mike_nunan]

I'm not going to get into the discussion of the physics here (seriously busy at work today) but I will say that the only serious drop that has befallen any of my lenses occurred when my Canon 85/1.8 flew out of a bag from nearly shoulder height and landed on stone. If it wasn't for the presence of the reversible plastic hood (in its reversed position) and a Hoya UV filter with any ally ring, I have no doubt that the lens would have been history. The thought of my Zeiss 85/1.4 undergoing the same sort of abuse makes me wince. There's no way it would have survived it. In this case, I believe both the design and the material of the hood played a part in minimising the shock to the bits that matter.

-= mike =-

 

[ante_portas]

I would add my angle of view to this. I would not like to repeat the same what was said above, so say this:fully metal bodies very often have a more quiet shutter.
The movement of the inside mirror is a existing danger for the final sharpness of photography, especially when body is plastic only. (for ex&le y fx-3 has 1/30 as a critical ex.time, although anyway belongs to quite good designed cameras- with comparing to other similar models).
This danger is very reduced with big metal body. Polycarbonate cameras also have limitations- with using of heavy lenses, or with using a tripod. I even saw a camera fully carbonate- bayonet and loading film track too...(other producer)
Nothing beats big heavy camera in stability, only bigger ones- or medium or large format! Weight has a sense... I am pretty much convinced that with metal body you achieve higher results, how much *higher* that's a question and a matter of direct comparing.

Plastic ones have another advantages for what are bought-menitioned already above.
just my observation, pavel

 

[afranklin]

Hi Pavel,

"The movement of the inside mirror is a existing danger for the final sharpness of photography, especially when body is plastic only. This danger is very reduced with big metal body."

I disagree, that is if you are talking about stability of the lense mount/mirror/focusing screen/film plane (which the assembly is called the mirror box) assuring accurate focusing. The body could be cardboard...it is the mirror box that is important, and I believe the Contax cameras that have polycarbonate bodies have metal mirror boxes, so this issue is mitigated at least with Contax.

If you are talking about sheer weight to d&en the shutter etc. yes, I agree, and a heavy lense like the 85/1.4 I believe makes for a wonderful d&ener on my Aria...and I have no problem shooting at 1/15 at 1.4 with that lense.

Regards,

Austin

 

[blumesan]

Hi Pavel

I think Austin has put it well. A heavy camera body will certainly decrease vibration due to mirror movement. But the simple solution to this problem is not to build a 5 kilo body; just provide a means to lock up mirror. Something that many manufacturers have neglected of late.

Regards,

Mike.

 

[bobbl46]

Physics? Inertia? Young's modulus of elasticity? D&ing factors? d = ut + 0.5ft*t ... All Greek to me!

All I know is that plastic (sorry, polycarbonate) don't show brassing, can be polished with care to take out minor scratches that would show base metal if the same amount of polishing was applied to metal.

It doesn't take off as much skin when it sticks to your hand in sub-zero temperatures.

Can take minor knocks and rebound without being permanently deformed.

On the other hand there is also a disadvantage ...

Can take minor knocks and rebound without being permanently deformed

(What! Deja Vu?)

..................

I have seen circuit boards hidden under the pentaprism that show impact damage, even though the outside plastic showed no damage at a cursory glance. Only on close inspection did the plastic show that the camera had taken a fair "whack"!

I did chuckle at the thought of a RTS III or an AX made of wood .... in fact I still am .... better still, an ND in finest rosewood ..... don't start me off again, please.

Cheers, Kyocera Kid.

 

[bobbl46]

Sorry ... didn't mean "under" the pentaprism .... meant under the pentaprism housing .... if you see what I mean!

Cheers, Kyocera Kid

 

[afong]

Fellow Photo-enthusiasts,

Choice of materials is only one aspect of good engineering. Which is best really depends on what your criteria for "best" is.

Then again, if your criteria is, say, survivability from a one meter fall onto a cement floor, then choice of material still is only one design parameter. In the case of a fall, damage does not depend on f=ma. The force on a body is relatively the same anywhere close to earth whether stationary or falling. The only time the force would be different would be if you are in space or on another planet. What is more of a concern is the difference of potential energy from a body at rest one meter from the ground to the potential energy from the same body at rest on the ground.

The basic law of physics says that energy must be conserved or rather the potential energy lost in the fall of a body must be converted into either heat, noise, or deformation of the material (this doesn't cover bouncing which would be converting the kinetic energy back to potential energy minus losses). Clearly, modern polycarbonate materials are more efficient at converting kinetic energy to heat or in effect absorbing the shock. Metal parts will tend to deform or transfer the energy. Again, either the energy causes the metal to bend or break or it is transfered to whatever is attached to the metal or it is returned to potential energy.

Survivability for a metal camera will depend on whether the transfer of energy can be dissapated by the rest of the non-metal parts or if the deformation itself, if any, causes the camera to malfunction. In the former case, the survivability will depend on the non-metal parts and metal parts inside the casing that are more fragile.

Ultimately, it is not cost effective to design a camera based on crash-survivability alone. Size and weight must also be considered. If they were not considered then the best camera to take an impact would be a massive sorbethane blob that would covert all kinetic energy to heat or massive metal exoskeleton that would deform but not transfer energy to the innards.

Obviously, the best camera has metal parts where you need 'em (where rigidity and wear are factors) and polycarbonate parts where it makes sense (size and weight, impact absorption, et al). All this in a package that isn't too expensive or made of unobtainium.

For those who have a look at the Aria, it is a beautifully engineered camera that is very compact and lightweight and mounts wonderful lenses.

Suggestion: don't drop your camera.

 

[alexw]

Perhaps I can add a piece of anecdotal evidence.

Last week I dropped an RTS with the 5fps drive and power pack coupled to a 300mm f2.8 Tamron from shoulder height onto a carpark. The lens which took most of the impact has a very large dent in the ring but the old RTS and its huge motor drive and power pack are fine. It has resulted in some damage to the focusing screen which isn't a major issue. There is a large dent in the car park.

 

[afong]

A camera in rosewood would be beautiful but not very stable when humidity changes.

Seriously, though, I appreciate my Aria when I travel. I carry so much as it is, having the Aria allows me to carry three primes in a compact pack. The camera is either around my neck or in my well padded bag. Therefore, I didn't consider its survivability in a fall to be a consideration when I bought it.