Magnesium bodies

Started Mar 26, 2012 | Discussions
Owen
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Magnesium bodies
Mar 26, 2012

I keep hearing about "build" quality of the new expensive cameras like Nikon, Canon, Sony.

Now I don't figure my camera is going to be run over by a car or truck so why add an expensive magnesium body to the build. New plastics are plenty strong for todays cameras.

What's more likely to happen is the camera will be dropped, the lens will be damaged or the more fragile insides will be damaged.

It seems better to add a thicker rubber coating to the camera to provide more protection than a stronger frame.

I dropped my Olympus E510 off my computer desk. It fell 2 feet onto a rug. No outside damage but the finder readouts and the flash stopped working. Now that wasn't even a hard fall.

Owen

Olympus E-5
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Osvaldo Cristo
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Precision
In reply to Owen, Mar 26, 2012

The main reason machinery industry goes to heavy and strong metal framing is to get dimensional stability independent of most environment variables and time of use. I guess that is valid also for cameras and their precise mechanics.

Probably there is some marketing elements on the decision also.

From my part I would never buy any plastic camera body while I have metal option at a reasonable price. I do not like the plastic feeling and for me Photography is a hobby - the pleasure is in the first place (Freud explains).

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Deleted1929
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Re: Magnesium bodies
In reply to Owen, Mar 26, 2012

A robust internal frame stops parts moving relative to one another. Without it internal component can flex and bend a great deal more. A rigid frame also creates a solid feel to a body which is very good for handling.

The use of Magnesium is an engineering choice for combined low mass and high strength properties. The ideal material would be Titanium, but it's rather more expensive ( about 200x the price of Magnesium ). If you know of something cheaper that has similar properties to Titanium then for goodness sake tell people because there's a huge queue waiting to form at your door, cheque books at the ready.

It seems better to add a thicker rubber coating to the camera to provide more protection than a stronger frame.

This would absorb a negligible about of shock and either add a great deal to the size of the body or force a more constricted internal design. It would not provide any rigidity at all.

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Alphoid
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Re: Magnesium bodies
In reply to Owen, Mar 27, 2012

Picture yourself as a National Geographic photographer shooting in Antarctica in the middle of snow storm. Picture your camera in your pack as you're rock climbing up Everest. Picture yourself as a photojournalist running around with your camera, dodging bullets in a war zone. Picture yourself as a wedding photographer, getting bumped by drunk guests, with an occasional drink spilled on your equipment. Picture yourself on the field of a football stadium, trying to get a photo of the winning team celebrating. Picture yourself as an amateur wannabe of any of the above.

If you're any of the above, weatherproofed, magnesium build is essential. Otherwise, it's something unnecessary you have to pay for -- in both price and weight -- in order to get the second control knob that only comes with a pro level body.

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Leonard Migliore
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Stiffness
In reply to Owen, Mar 27, 2012

One big difference between plastic and metal is stiffness. This is typically quantified by the material's elastic modulus. Magnesium, which is about 40% denser than polycarbonate, has an elastic modulus 16 times larger. So a magnesium structure that's the same weight as a polycarbonate structure will deflect 1/12 as much. This is good for stuff like optics that you would like to keep in one place.

As it happens, most metals have similar ratios of stiffness to weight. Oddly, titanium is on the low end of this scale. What you really want is beryllium, which is 6 times stiffer than magnesium and has about the same density. Of course, it's hideously expensive and toxic, but it would make a nice camera body; a lot of optical devices in orbit are made of beryllium for the reasons I've described.
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Owen
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Re: Magnesium bodies
In reply to Alphoid, Mar 27, 2012

Alphoid wrote:

Picture yourself as a National Geographic photographer shooting in Antarctica in the middle of snow storm. Picture your camera in your pack as you're rock climbing up Everest. Picture yourself as a photojournalist running around with your camera, dodging bullets in a war zone. Picture yourself as a wedding photographer, getting bumped by drunk guests, with an occasional drink spilled on your equipment. Picture yourself on the field of a football stadium, trying to get a photo of the winning team celebrating. Picture yourself as an amateur wannabe of any of the above.

If you're any of the above, weatherproofed, magnesium build is essential. Otherwise, it's something unnecessary you have to pay for -- in both price and weight -- in order to get the second control knob that only comes with a pro level body.

Yes I agree with you but, It is the electronics and the rest of the insides that are still as fragile as if they were in an all plastic body. All mechanical bodies like 35mm are far more reliable than electronics and their plugs which can jar loose.

Owen

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Berghof
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Leonard I think you know what you are talking about, thanks
In reply to Leonard Migliore, Mar 27, 2012

yes, you know your metals, thanks
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wb2trf
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Is all marketing (and pleasure)
In reply to Leonard Migliore, Mar 27, 2012

The post about "pleasure" has got it right: pleasure and marketing is what is driving this. No one has any testing results to point to, and the answer is not obvious without testing. Volvos once reflected the view that a car frame should be stiff, then it was decided it should be selectively crushable to reduce g forces. Should a body work to distribute and reduce impact forces or to be stiff. Only lots of testing would show.

Either plastic or metal can be made weather/water resistant. So that is irrelevant. Also electronics are generally more easily made shock resistant than mechanical components, although added glass in the form of the display panel in the back, not just the lens in the front, increases risk.

To test one would need to know the probability of various kinds of damaging impacts and whether the case should optimize for stiffness or reduced g forces on internal components. Then one would need to design to neutralize the most probable risks. Is that done? There is no evidence that it is.

(BTW: I subjected a P&S camera to a mild blow, which broke the focus mechanism internally somehow. I was on a long camping trip and very distraught over the loss. After some testing I decided I had nothing to lose by dropping it again with an equal impact on the opposite side. That fixed it.)

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steephill
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Price, weight and quantity
In reply to Deleted1929, Mar 27, 2012

Titanium alloys are about 4x more expensive than magnesium alloys. And magnesium alloys are 2.5x less dense than titanium alloys so for lowest mass you would go for magnesium.

The amounts involved in camera manufacture are very small so relative material cost is not a major issue. Ease of manufacture and mechanical properties are the important criteria.

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Leonard Migliore
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Re: Price, weight and quantity
In reply to steephill, Mar 27, 2012

steephill wrote:

Titanium alloys are about 4x more expensive than magnesium alloys. And magnesium alloys are 2.5x less dense than titanium alloys so for lowest mass you would go for magnesium.

The amounts involved in camera manufacture are very small so relative material cost is not a major issue. Ease of manufacture and mechanical properties are the important criteria.

Ease of manufacture (or the lack thereof) is a big downside of titanium. It's expensive to cast and very miserable to machine. And it tends to crawl around on you after processing, which is the last thing you want in a camera frame.

Magnesium is readiily die cast and machines like a dream; that's probably why camera designers like it over aluminum, which is about equal in stiffness-to-weight. Its only downside is that it has poor ductility, so that it cracks rather than bends. But a bent camera body is no better than a cracked one.

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Bill Force
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Re: Stiffness
In reply to Leonard Migliore, Mar 28, 2012

Very true until you get into "matrix metals" such as they use in helicopter seats, bicycle frames etc. Extremely strong and light weight and they do not crawl like some metals. I've always wondered why someone hasn't used this compound in camera bodies?
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Leonard Migliore
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Re: Stiffness
In reply to Bill Force, Mar 28, 2012

Bill Force wrote:

Very true until you get into "matrix metals" such as they use in helicopter seats, bicycle frames etc. Extremely strong and light weight and they do not crawl like some metals. I've always wondered why someone hasn't used this compound in camera bodies?

Metal matrix composites, like boron fiber in aluminum, are indeed stiff and strong. They also be dogs to cut threads in. This makes them fairly unsuitable for things like cameras, which tend to have a lot of tapped holes in the main structure.

That's also why carbon fiber reinforced polymers aren't too common for this use. Graphite-epoxy is really stiff and light. The problem is, you have to incorporate inserts in them anywhere you want to attach something, like a lens. No way you would do this in a consumer item.

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Bill Force
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Re: Stiffness
In reply to Leonard Migliore, Mar 28, 2012

I agree, I raced alumimum engines for 20 years and had to "insert" every bolt hole in the entire engine.
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mandm
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Nikon offered film cameras with Titanium bodies
In reply to Leonard Migliore, Mar 28, 2012

Nikon F2T & F3T outer bodies were Titanium, the inside was the same as the standard bodies; As was the Olympus OM4 T and their are others. They go for big bucks today as not many were made, some were anniversary models and some came in custom real wood boxes.
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KenCK41
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Re: Nikon offered film cameras with Titanium bodies
In reply to mandm, Mar 28, 2012

I don't think its been mentioned, but the metal bodies will hold up better with big lenses (i.e. 300/2.8 type) It doesn't take much to rip the mount of my d90 right of the front of the mirror cage. This usually ruins the camera.

Also I disagree with the old mechanical was reliable and modern electronic is fragile.

Most failure of pro digital gear are mechanical failures due to extreme usage rates.

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Bill Force
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Re: Nikon offered film cameras with Titanium bodies
In reply to KenCK41, Mar 28, 2012

Whether YOU agree with it is moot, I still have and use 6- 35mm vintage cameras (4 diff. brands) and they are all in perfect working condition. Conversely I have a whole big box full of disabled and useless digital PLASTIC cameras that have 'bit the dust" and are only there for parts. History has borne out that the all metal mechanical cameras are vastly superior for longevity.
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Dan Marchant
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Re: Magnesium bodies
In reply to Owen, Mar 29, 2012

Owen wrote:

Yes I agree with you but, It is the electronics and the rest of the insides that are still as fragile as if they were in an all plastic body. All mechanical bodies like 35mm are far more reliable than electronics and their plugs which can jar loose.

Owen

As explained by a previous poster, the electronics will always be vulnerable regardless of if the body is magnesium or plastic. - the mag body has nothing to do with protecting the innards against large shocks (such as being dropped) it is to do with the long term durability under normal operating conditions. A hobbyist will shoot occasionally so a plastic body will be fine; but pros need a camera that will shoot all day long, day in day out and often in adverse conditions (weather sealing). That means they need the better build quality and durability that comes from a mag body.

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T3
T3
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lenses mount to plastic subframes
In reply to Leonard Migliore, Mar 29, 2012

Leonard Migliore wrote:

One big difference between plastic and metal is stiffness. This is typically quantified by the material's elastic modulus. Magnesium, which is about 40% denser than polycarbonate, has an elastic modulus 16 times larger. So a magnesium structure that's the same weight as a polycarbonate structure will deflect 1/12 as much. This is good for stuff like optics that you would like to keep in one place.

This might all be good and well, but what many people don't realize is that the lens mount of many of these magnesium camera bodies actually mount onto plastic subframes made of stiff engineering plastic!

When people look the lens mount of magnesium alloy bodies like the Canon 10D-50D, 7D, or 5D-5D MKII, they assume that the lens mount is attached directly to the magnesium alloy body. But if you remove the shiny metal lens mount, you'll find that it actually attaches to a subframe made of stiff engineering plastic:

It's this subframe of engineering plastic that is really keeping everything in place. The lens mount attaches to this plastic substructure. The tripod mounting socket attaches directly to this plastic substructure. The surrounding magnesium shell is mainly there for show: cosmetics, feel, and marketing. Also, many people also may not realize that the bottom plate of Canon's magnesium 10D-50D, 7D, and 5D-5D MKII bodies are also plastic. If you have any of these bodies, just turn them over, tap on the bottom plate, and you'll see for yourself.

Also, some bodies, such as the Nikon D7000 exemplify this "magnesium for show" principle even more. Many people know the D7000 as having a magnesium body, but the reality is that only the top and back plate are magnesium. Everything else is plastic.

The reality is that whether you're using a plastic-body DSLR or a magnesium-body DSLR, you're not going to see much of any practical difference in their capacity to carry a lens and keep it in place. Over the course of years, I've owned the Canon Rebel XT, 10D, 20D, 40D, 5D, and 60D. They all support lenses just fine, even heavy ones. And the really big lenses have tripod collars to support their weight. I currently own the 40D, 5D, and 60D, and when I mount my 100-400L IS on any of these bodies, they all support the lens just fine. No difference.

Ironically, someone who owns a Nikon D7000 might brag that his camera is stiff because it has a magnesium body, but he may not realize that the magnesium in his D7000 is limited to cosmetic plates on the top and back of the camera only. It's really the D7000's tough, stiff, engineering plastic subframe that is doing all the work.

It's only the high-priced bodies like Canon's 1-series or the Nikon D800 that have subframes that are magnesium. Just don't expect that you're getting the same thing with lower-priced magnesium bodies.

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mandm
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My 1969 Nikon F is still working great
In reply to Bill Force, Mar 29, 2012

I only shoot 2 rolls a year in it, but it's still a great camera and when digital users hold it they are always impressed with the feel of the body and the lenses like my Nikkor-H 300mm 4.5 or even the 28mm 3.5 (both Non AI).

When showing off my 4x5 Graflex, they don't understand how that could ever be a field camera and used in WW ll, Spoiled.

A metal body mount screwed into the metal mirror box is much stronger than anything screwed into space-age plastic. I don't ever recall see or hearing about a lens ripping the front off any of the Nikon F's, bit I have seen bodies with the front mount ripped off, some only with 100-300mm on them.
The good old days, but my 59 year old eye's do like AF.

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Leonard Migliore
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Nice examples
In reply to T3, Mar 29, 2012

I really can't figure out why they would do this; if you're going to the trouble to use a metal frame, you really should attach the important parts (lens and sensor) to that frame; everything else can flap around freely but you do want the optics to be precisely located.

If you're putting the optical elements on plastic you might as well make the frame out of goat cheese.
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