Would you consider the 70D to be

Started Jul 7, 2013 | Discussions thread
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not really. Misconceptions of the role of magnesium,
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 stronger than a composite body and handles the weight of heavier lenses without flexing.

It's a myth that the magnesium is actually bearing much of any lens weight. What many people don't realize is that most of the load-bearing structure of a camera is made of high strength engineering plastic. If you remove the metal lens mounting ring, you'll find that the metal lens mounting ring is actually attached to a core structure made of engineering plastic. It's that plastic you see inside the camera body when you remove the lens.

Lens mount attaches to plastic inner core, not to magnesium.

Here's what it looks like when the lens mounting ring is removed, revealing the plastic substructure on which it is mounted. As you can clearly see, the stainless steel lens mount attaches to PLASTIC, not to the magnesium shell.

Lens mount removed, revealing the plastic core structure into which it is mounted.

Here's the Nikon D7000, which only has magnesium top plates (shown below on left) with even more of the plastic substructure revealed. Again, the load bearing structure onto which the lens mount is attached is plastic.

Plastic substructure revealed.

In bodies using lighter plastic out shells, the internal engineering plastic substructure is typically supported by stainless steel supporting plates, here seen in purple in one of the Canon Rebel bodies:

Structural diagram of Canon Rebel body.

And another thing many people may not realize is that the bottom plate of most prosumer magnesium bodies, including the Canon 7D, is made of plastic, as I mentioned in a previous post. So you have the metal tripod socket, and metal lens mount, both attached to the tough plastic internal core structure, and a lot of other components integrated into this central plastic core structure, too. Literally, plastic is the "heart" of the camera. But most people don't realize this, because they're too in love with the external shell to even notice.

So my main point is that even with all the magnesium (or plastic) exterior body shell components removed, the underlying substructure is still able to support the weight of a heavy lens. The outer shell, whether it's made of plastic or magnesium, is just that--- an external shell. It's not really there to bear much lens weight, and the differences between a plastic shell versus a magnesium shell, in terms of how much stiffness or strength they contribute to holding a lens, are mainly cosmetic and superficial. The high end 1-series Canon bodies, as well as Nikon's top-tier bodies, are made differently, with more of a monocoque magnesium structure, so magnesium plays a much greater role in the strength and stiffness of those bodies. But for all the other magnesium DSLRs you see, magnesium is mainly just an external, cosmetic shell.

You also have to keep in mind that any lens with enough weight and mass to flex a camera body is going to have its own tripod mount anyways. At that point, the camera body is hanging off the lens, not vice versa (lens hanging off the camera body). So body stiffness becomes a non-issue.

For me, I've been using Canon's magnesium DSLR bodies (10D, 20D, 40D, 5D, etc) for a while now, and then I got the 60D. And I've noticed ZERO differences in body stiffness, regardless of which lens I've used on it. Obviously, if I'm going to tripod mount my camera with a 70-200/2.8L or 100-400L IS, which I regularly do, they have their own tripod mounts. And I wouldn't test the camera body's capacity to bear the weight of those lenses, regardless of what material the camera was made of. So suffice it to say, people who worry that they need a magnesium body because it will flex less with heavy lenses shouldn't worry at all about it. Buy magnesium because you like the feel of it, nothing more.

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