Introduction I thought it might be a good idea to have a specific thread for discussion of camera construction and materials so as to avoid hijacking other threads with the topic... So here's a thread for facts, opinions, whatever. There are many misconceptions in and around photography, most of which have been spread since the dawn of the internet, but many of which are also spread by photographic journalists who aren't necessarily experts in particular fields that perhaps only touch photography tangentially. One of the main such misconceptions lies in the field of materials for camera construction, and the associated but separate area of build quality. The commonly-held view by those ignorant in the field of materials science and technology is that metal is somehow inherently better than "plastic" in every case, and that "plastic" is just cheap and nasty. As with most misconceptions, there's some truth in it, but it's far from a universal truth. "Plastic" We tend to use the word indiscriminately to describe any polymer-based alternative material, but the reality is that we're talking about a whole spectrum of materials from ones that are indeed cheap and nasty through to some of the most sophisticated and high-tech composite materials available. Many of these materials have been developed to have specific characteristics that make them stronger and more suitable than "metal" alternatives; applications include aircraft and car body parts, and some of the more familiar materials include carbon fibre and kevlar. Even tank armour is a composite material these days, albeit using ceramics: it's used because it's much stronger than steel. One of the big advantages of these materials is that they don't deform plastically, i.e. they don't dent; typically, they can absorb large stresses without failing. "Metal" Actually, we tend to use this word pretty generically too to cover a multitude of materials and construction methods. Historically, the outer skin of cameras was often chromed or painted brass, which often looks lovely when worn. This is a material which deforms plastically, and many older cameras bear several dents as battle scars. In some cases, these dents can be the sign of the material having failed to do its job of protecting internal components, but in most cases, they're purely cosmetic. Many late 70s-early 80s SLRs used topplates of not much more than metal foil - these provided very little protection, but the reality is that very many of these cameras have survived regardless. Finally, we have modern magnesium alloy castings. These don't deform plastically, but can fracture - in fact their properties are very similar to several engineering polymers and composite materials. Their one theoretical advantage is that they will survive very high temperatures better, but these sort of temperatures will be outside the working temperature of the rest of the camera anyway. Aesthetics/Tactility This is of course a highly subjective area, but it's probably fair to say that people don't like "plastic-looking" or "plasticky" cameras, and prefer the feel of metal. I can't much disagree with them. That said, it can actually be pretty hard to tell them apart either by look or touch in some cases. Popular opinion and marketing We tend to associate "plastics" with low-end products, and "metal" with high-end ones for cultural and historical reasons, and in part at least because it's often true that these are the materials used. At the low end of the market, it's undeniable that "plastics" are used because they're cheap and do an adequate job. At the top end, the reality is that engineering polymers and composite materials can do at least as good a job, sometimes better, but the best materials are not necessarily cheap, and the manufacturers have to battle the resistance of the market - the lack of knowledge in the area, and also the issue of tactility. Build Quality Many people appear to equate build quality with weight, or the use or otherwise of metal. This isn't a very good way of looking at it: build quality is really an issue of the selection of appropriate materials to protect the delicate innards of the camera, and the way it's put together and smoothness of operation. A few case studies A few thoughts based on several cameras I've owned or have knowledge of: Canon EOS 100 (and 1000) and Nikon FM2n - in the early 1990s, I finally had the funds available to buy a decent camera. I had been planning on an OM4 Ti, but prices doubled pretty much overnight. I would've loved a Contax, but they were similarly out of reach. My choice came down to an FM2n or an AF camera, either a Minolta, Nikon or Canon. I didn't like the Minolta and the F601's AF was frankly risible. The EOS 100 was fantastic in terms of AF, very quiet but didn't appear to be brilliantly well-made -the materials used and build were OK but not great. The FM2n was very solid, but it didn't really feel all that well made - more agricultural than a precision instrument, certainly not as nice as the OM I had had my eye on, and nothing like a Contax. 20-odd years later I still have that camera, and it still works perfectly. It has been used in temperate and tropical rain forests, in deserts, and in snow and ice; it's been knocked and bashed on walks and scrambles all over the place. It's been dropped, soaked - you name it, it has been through it - and survived. A few months later, I was going to buy my wife a 1000, but when we looked at it, we thought the build quality was terrible - creaky panels and thinner plastic. So I got her a 100 instead. That has had a similar life to mine, and still works. It did have to have one repair - we were running full tilt over a stone bridge near Rosslyn Chapel when the neck strap failed (user error) and the camera went flying through the air before bouncing several times. Although the camera was scraped, the only issue was that the click stops on the mode dial failed, and had to be repaired. That camera too is still working now. These cameras are clearly a lot more robust than might be expected, and are as smooth in operation as the day they were born. Some years ago, I bought a s/h FM2n, and it reinforced my earlier feelings - I actually hated it, and sold it. (Incidentally, I loved my FE and really wish I hadn't sold that.) Canon EOS 3 There was quite a fuss when this camera appeared - why wasn't it made of metal, people were asking on nascent photographic forums? Well one reason was that it replaced the EOS 5, which was also plastic - but the 3 is very much better made than the 5, which is frankly a bit ropey. Again, this camera has well and truly stood the test of time - in fact mine is in a much better condition than my magnesium alloy bodied EOS 1v despite having had a lot more use. EOS 60D By the time this camera was launched, the anti-plastic lobby was quite rabid, and couldn't understand why Canon would choose to make it plastic rather than metal. None of them had ever picked one up, of course, and thus had failed on the realisation that it's actually a very well-made camera that's a touch lighter and better waterproofed as a result of the choice of material. EOS 6D Another camera criticed primarily by those who have never used one, the 6D eschews a metal top-plate to allow GPS reception and WiFi transmission. It also shaves a few grammes off the weight. However, the camera feels no less substantial as a result - it's a very well-made machine. So which is best? For cheap cameras, costs are clearly kept down by using cheaper materials. The reality is that these are almost certainly tough enough for the vast majority of people. For mid to high range cameras, better materials are appropriate. There's very little in it in terms of material performance between magnesium alloy and the better polymers and composites - in fact high-end composites are probably the best materials in terms of properties, but the reality is that any of these materials will take pretty much whatever you throw at them - or indeed pretty much anything you throw them at. The reason why metal predominates is down to the tactile properties, and the fact that people's perception is that metal is better. It doesn't really matter that it's not true, and the gains in changing material type aren't really significant enough to try to re-educate people. At the end of the day, preference outweighs any marginal gain in strength, weight or cost reduction.