Is Metal > Plastic? Not When It Comes To Lens Mounts, According To Lensrentals

Every once in a while Roger Cicala from Lensrentals debunks a myth. Today on his operating table is the Plastic vs. Metal lens mount myth.

Many photographers (me included) think that pro grade lenses are equipped with metal mounts rather than plastic ones. It makes perfect sense, right? Metal is stronger than plastic.

Well, according to Roger, we are all in the wrong.

As a person who takes lenses apart all day (every day) Roger is pretty informed about lenses, and while he does not provide accurate statistics, his rental house goes through hundreds of lenses of all kinda and types so his reports about what breaks and what is solid should be taken seriously. Roger tries to address some of the “facts” that popped up after the a few reports on the Olympus 12-40 breaking on the plastic mount.

His first interesting finding is that many lenses that the “internet considers” to be metal mounts are actually plastic mounts, including the Pro Canon 35mm f/1.4 L lens – a 15 years old lens and the Canon 24-70 f/2.8 L Mk I – which has a newer mkII model. This one carries over 2 pounds of glass off that plastic mount.

“Canon 24-70 f/2.8 L Mk I. A professional lens released in 2002. It weighs about 2 pounds; far larger than any two micro 4/3 lens combined. It is generally referred to as a tank because it never breaks (it has optical problems, but those occur at the front end, which is, oddly enough, entirely made of metal). The plastic mount never breaks despite holding up 2 pounds of lens. Trust me on that, we’ve carried hundreds and hundreds of these for years and never had a mount break. (As an aside, the Mk II version has a metal mount, despite being lighter. I’m not sure why.)“

His other interesting observation is that there is probably no connection between the material the mount is made of – metal or plastic to the likelihood that a lens will break.

“The pictures show that for many years lots of very large, very high-quality, professional-grade lenses have had plastic internal mounts. Guess what? They didn’t all self destruct. In fact several of them are widely considered particularly rugged. Looking at 7 years worth of data involving around 20,000 lenses I can’t find any suggestion that plastic mount lenses, in general, fail more than metal mount lenses. Sure, there are certain lenses that fail more than others, but not because they have a plastic mount.

In theory, plastic mounts might be better, worse, or no different than metal as far as reliability goes. There are logical arguments for each.“

The post goes on to debunk another myth about weather resistant lenses – you’ll be surprised what it means.

[Assumptions, Expectations, and Plastic Mounts | Roger Cicala and Aaron Closz]