Magnesium vs. Plastic Body Construction

Plastic degrades over time becoming brittle and weak.

Yusef wrote in post #11162423
Plastic degrades over time becoming brittle and weak.

How many lifetimes are we talking before a 550D turns brittle?

tkbslc wrote in post #11162333
I don't see how that is a knock to modern camera construction. If put a small hammer in my camera bag ($5 at the hardware store) then I can also hammer in a nail and then take a picture with my 30D. Why would I want to hammer in a nail with a camera when a $5 tool does the job better?

I was agreeing with the point I'd quoted that the electronics in a DSLR probably can't stand impact that would leave the case undamaged...which mechanical cameras could do.

CyberDyneSystems wrote in post #11161095
Plastics may be better in a lot of cases, but it is certainly more affordable and easier to cast.
I think the largest part of the reason Canon could afford to drop the launch price of the 60D was this one change. Magnesium alloys are far more costly than the plastics, whether it is superior or inferior,. it is more costly to produce.

Bingo! We have a winner!

But back to the original question:

ABS plastic is much more resistant to impact damage than magnesium. Canon says so. And if we look at a dozen or so threads in this forum on the lines of "Waaah! I dropped my camera!" we'll see pictures of magnesium bodied cameras badly cracked. I can't find it right now but there was a good picture of a cracked 5D a while back.

Magnesium is light and brittle. ABS is heavier and resilient.

They make motorcycle helmets from ABS plastic. They never make them from magnesium.

-js

tkbslc wrote in post #11161993
Somehow, carbon fiber is accepted as high quality, but other composites are considered "cheap", regardless of actual properties.

This one I don't understand either--as carbon fiber shatters on impact

Yusef wrote in post #11162423
Plastic degrades over time becoming brittle and weak.

Modern plastics are exceptionally durable.

It's not 1970 anymore.

If you question the durability of plastic bodied cameras, I suggest you watch these videos.

http://www.youtube.com​/watch?v=D1tTBncIsm8
http://www.youtube.com​/watch?v=FWzsXeXCwuc

tharmsen wrote in post #11163134
If you question the durability of plastic bodied cameras, I suggest you watch these videos.

http://www.youtube.com​/watch?v=D1tTBncIsm8
http://www.youtube.com​/watch?v=FWzsXeXCwuc

Fun videos!

tharmsen wrote in post #11163125
Modern plastics are exceptionally durable.

It's not 1970 anymore.

It's a very good remark, "not 1970 anymore", it's hard for some that grew up in the 60s or 70s to think high strength plastic is better than metal of any kind.

I'm in the civil engineering field, we use HDPE (High-density polyethylene) which is a is a polyethylene thermoplastic made from petroleum, we also use a very high strength grade of PVC pipe which is also another type of plastic. Yeah I know is not the same but this is an industry where everything was either ductile iron pipe or some other high strength concrete pipe design for very high pressures in either water mains or force mains. It took people a very long time to realize that plastic was better for many applications plus it made it easier to handle and in some cases such as with PVC much cheaper to build.

It's hard fact to swallow for some but high strength plastic is just as good as many metals out there. I personally never had a problem with it, and I don't think magnesium is any better than a good high grade, high strength plastic.

I don't think plastic vs. magnesium really matters. Ergonomically, I found my old Pentax K10D to be equal to or better than the mg-body 40D. It had full weather-sealing and was leagues ahead of the Rebel Xti, Xsi series.

Anyone else notice the disappearance of the OP?

Destractions wrote in post #11164146
Anyone else notice the disappearance of the OP?

It seems OP started a forest fire. Fun to debate the issue though.

Very interesting debate indeed.

I agree with whoever mentioned earlier about there being a psychological edge to magnesium. As someone above mentioned, growing up, we never think of plastic as being strong. Most plastics people encounter in their day to day lives that we are aware of (big distinction between knowing something's plastic and not knowing!) wouldn't inspire confidence in protecting a camera body. Plastics are so varied in their application, so it's hard to think of something that you chuck a couple of oranges in at the supermarket is related to something used on ultra high tech machines.

I don't doubt that plastics have come a long way in a short time. Magnesium alloys to me feels better in my hands. That's not a very scientific point I know, but a lot of people make decisions on what feels right rather than what is technically superior.

Destractions wrote in post #11164146
Anyone else notice the disappearance of the OP?

Ummmm, he was "disappeared". Best not to speak of it further. Shudder.

AdamJL wrote in post #11164326
I don't doubt that plastics have come a long way in a short time. Magnesium alloys to me feels better in my hands. That's not a very scientific point I know, but a lot of people make decisions on what feels right rather than what is technically superior.

Even the feel is changing.

I'm an amateur machinist, just as I'm an amateur photographer. (Except that I've actually made money with my lathe, milling machine and welder.) Amateur because I have no interest in destroying my love for a hobby by trying to turn it into a business.

A few years ago I had occasion to machine some pieces from Delrin stock. (Generic name is Acetal.)

Amazing stuff. Machines beautifully to a nice finish on the first pass. Easy to achieve tolerances of .001". Stable stuff, too. Untouched by most nasty chemicals.

As enrigonz observes, HDPE is also a very useful material. Excellent for making patterns, for example - you can cut and machine it to precise dimensions with hand tools.

And, of course, PVC is ubiquitous these days in piping. The high-strength stuff is available too, and cheap. No problems with rust!

(Yeah, I'm a gearhead.)

-js