Would you consider the 70D to be

Started Jul 7, 2013 | Discussions thread
T3
T3
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Re: No.
In reply to Midwest, Jul 9, 2013

Midwest wrote:

T3 wrote:
Frankly, I prefer the composite body. Modern plastics are extremely resilient, dissipate impact shock better, are lighter, are far less prone to cracking and denting, compared to magnesium. Magnesium is very stiff, but as a result it's not as resilient so it's more prone to cracking. Plus, paint can chip and scratch off a magnesium body, which isn't an issue with a composite body.

I did some reading on the Internet to find out the lowdown on magnesium bodies and why they are used in more expensive cameras. These are some of the points I saw:

1. Magnesium makes a more solid camera body, no flexing, supports heavier lenses better.

2. Magnesium body fasteners can be assembled more tightly than plastic body fasteners.

3. At least some plastic body cameras have mounting screws (such as the lens mount) that go straight into the plastic, which can actually be torn loose - and again these cannot be tightened as much as regular screw-and-nut type fasteners.

4. More rigid magnesium body makes the mirror box more rigid as well, allowing it to operate reliably at higher FPS. (That came from a big shot at Canon in a video I saw.)

These assertions are false.  See my post above: http://www.dpreview.com/forums/post/51775114

1. Aside from Canon and Nikon's pro bodies which more of a monocoque construction, the prosumer bodies mainly just use magnesium as an external, cosmetic shell.  The internal substruction onto which these external shell plates are mounted is actually plastic.

2. I have a 40D and a 60D sitting in front of me at this moment, and without actually touching them, I'm hard pressed to tell which one is plastic and which one is magnesium.  Clearly, the plastic 60D is not built any less "tightly", and conversely the 40D is not built "more tightly".  Furthermore, we're not taking about magnesium panels welded to one another.  We're talking about magnesium panels fastened via tiny screws onto a substructure (that is comprised of mainly plastic, along with internal steel plates, which are really responsible for the camera's structural stiffness, not the exterior magnesium).

3. Actually, the lens mount is mounted to plastic, EVEN ON MAGNESIUM BODIES!  See photos below:

If you don't believe me, just remove the screws from your 7D (or whatever magnesium body you currently own).  The lens mount screws go into plastic.  Bet you didn't know that, did you?

4. This statement is probably the most ridiculous one of all, since all mirror boxes, except possibly with the exception of Canon's or Nikon's flagships, all have plastic mirror boxes.  And as the top photos show, even the lens mount attaches to this plastic substructure that houses the mirror boxes.  And on top of that, the bottom plate of these magnesium bodies, including the 7D, is plastic, too!  And the tripod socket mounts into the plastic internal core substructure!  Yes, that bottom plate surrounding the tripod mounting socket is plastic:

It's the part that survived, while the adjacent magnesium failed, in the photo below:

The reality is that, whether the exterior shell is made of plastic or magnesium, it's really the role of internal steel plates and the solid engineering plastic core that provide the support and stiffness for the camera.  You can see some of the internal steel plates below, in this Canon 5D MKII dissassembly.

Tellingly, in spite of the 5D MKII having an external magnesium shell, it still has those internal steel plates.  If the magnesium shell really was the source of a camera body's structural stiffness, then there really would be no point in those additional steel plates.  But the reality is that, regardless of the external shell material, those steel supporting plates are in all of Canon's bodies, including the Rebels.  Then, in front of those plates, and the circuit board, you have the tough mirror box and shutter assembly, made of engineering plastic.  And all the way in the front, you have the lens mount attached to this plastic core.

People really need to get over their worship of magnesium, and their dismissiveness towards plastic.  The reality is that you could literally remove all the magnesium external shell plates of a 7D, leaving only the plastic substructure, and it would still hold a lens just fine!

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