Scary realisation with extension tube...

I was out and about on the weekend rocking the 6D with my new 70-200 f/2.8 II and athird party extension tube for some close up stuff.

About half way through the morning when I was taking it off for a bit I realised that the actual mount on to the camera is only a plastic one, the side you fit the lens to is metal though. After that I was taking extra care whilst handling the rig when with the extender on.

The 70-200 is no feather weight, has anyone ever seen a plastic mount break with such a load on it?

I've used my 300mm f/4 with a full set of tubes and would always hold it in a way where it was fully supported on the lens and camera end.

My 6D has a metal mount that appears to be screwed to a metal frame. The heaviest lenses I own are the 100-400L and 70-200 2.8 OS. I use them a 6D and 60D with no issues. Of course, I don't handle those setups like I've got a 50 1.8 mounted, either.

My bad. I see you are talking about the TC being plastic, not the camera. Forgive me. I need coffee.

GeoKras1989 wrote in post #17019604
My 6D has a metal mount that appears to be screwed to a metal frame. The heaviest lenses I own are the 100-400L and 70-200 2.8 OS. I use them a 6D and 60D with no issues. Of course, I don't handle those setups like I've got a 50 1.8 mounted, either.

He is talking about a plastic extension tube mount not the actual camera body mount.

I own a pair of polymer (plastic) bolt cutters. As in, they are designed to chew through hardened steel, and do a wonderful job at it. (They are non-reactive, and non-conductive, so they won't spark or cause other potential hazards in high risk environments.)

The point is that being 'plastic' doesn't matter. What matters is how strong that plastic is, and how resilient it is.

Also don't forget that the metal lens mount on many of those high end lenses screws into plastic pieces. Far better to have the relatively easy to work on mount/lens fail than to risk the harder to work with camera (which has more stuff to damage.)

Luckless wrote in post #17019627
I own a pair of polymer (plastic) bolt cutters. As in, they are designed to chew through hardened steel, and do a wonderful job at it. (They are non-reactive, and non-conductive, so they won't spark or cause other potential hazards in high risk environments.)

The point is that being 'plastic' doesn't matter. What matters is how strong that plastic is, and how resilient it is.

Also don't forget that the metal lens mount on many of those high end lenses screws into plastic pieces. Far better to have the relatively easy to work on mount/lens fail than to risk the harder to work with camera (which has more stuff to damage.)

They are third party extension tubes, unsure how good the plastic is, good old Jessops ones.

I've read stories before of the 50mm 1.8 II breaking and getting stuck in the camera mount.

In fact a quick google search uncovered this.

http://www.theroastedr​oot.net …on-50mm-f1-8-camera-lens/

Luckless wrote in post #17019627
I own a pair of polymer (plastic) bolt cutters. As in, they are designed to chew through hardened steel, and do a wonderful job at it. (They are non-reactive, and non-conductive, so they won't spark or cause other potential hazards in high risk environments.)

No, you don't. You have a pair of plastic HANDLED bolt cutters with hardened steel jaws.

Luckless wrote in post #17019627
The point is that being 'plastic' doesn't matter. What matters is how strong that plastic is, and how resilient it is.

The "point" is you probably shouldn't be commenting about this.

+1 to corndog cabernet, I'm not aware of any composite or polymer that can cut steel. It's just not possible.

Not to say that a strong composite material can't be a good lens mount though, but it's not the cheap plastic they use on lenses and cheap extension tubes, and metal is probably cheaper than a high grade composite material.

I would fear any 'extra' stress on the mounts regardless of the material being plastic or metal.
Metal could just as easily crack rather than dent when abused.

There is the old myth that a 'mostly' metal lens or body is superior because it is a heavier weight.
The example is the older non USM 100mm Canon macro, and it is built like a tank.
Many users look at the 100L, pick it up and immediately dry inferior materials.
The point is this claim is made without researching either materials used to make those lenses.
If i drop the old lens the metal dents, and it can't be used.
If I drop the new lens the plastic breaks apart, and it can't used.

As other have stated the reliability comes from the 'true quality' of the material used to make that TC
Hold one hand on the camera body and one hand under the lens as often as possible.
I have used my Life Size Converter often on my 100L, always supporting both ends, and it has metal mounts.
The better you treat your gear the longer it will last. Many primes lens still function at 100% decades later.

InfiniteDivide wrote in post #17020120
I would fear any 'extra' stress on the mounts regardless of the material being plastic or metal.
Metal could just as easily crack rather than dent when abused.

There is the old myth that a 'mostly' metal lens or body is superior because it is a heavier weight.
The example is the older non USM 100mm Canon macro, and it is built like a tank.
Many users look at the 100L, pick it up and immediately dry inferior materials.
The point is this claim is made without researching either materials used to make those lenses.
If i drop the old lens the metal dents, and it can't be used.
If I drop the new lens the plastic breaks apart, and it can't used.

As other have stated the reliability comes from the 'true quality' of the material used to make that TC
Hold one hand on the camera body and one hand under the lens as often as possible.
I have used my Life Size Converter often on my 100L, always supporting both ends, and it has metal mounts.
The better you treat your gear the longer it will last. Many primes lens still function at 100% decades later.

Absolutely this.

Everyone likes to believe that metal is somehow superior when it comes to all these camera components, for some it can certainly be better, but it isn't always.

I dropped my Fuji XF 35mm a few weeks after buying it, only from a few feet. It's a fully metal lens... guess what, dented the aperture ring and now it's very hard to get it to stop down to f/8 and beyond. I dropped my old plastic 35/2 from the same height and absolutely nothing happened to it say for a scrape in the paint.

I wouldn't worry too much about your tube OP, unless you think it feels flimsy. Does sound odd though, which tube(s) do you have? I have some cheap generic ones from Amazon and they're fully aluminum.

Here's my take FWIW….

Stainless Steel mounts are far stronger than plastic, no doubt. This is much about the cross sectional dimensions of the bayonet and the leverage placed upon it.

Regarding camera housings, my experience is that the magnesium top plate cracked on my 7D in a simple tripod tip over. I am convinced that if it had been FRP (fibre reinforced plastic) it would have been OK.

Neither of these materials should be dubbed inferior, it's just horses for courses.

EverydayGetaway wrote in post #17020154
..
I dropped my Fuji XF 35mm a few weeks after buying it, only from a few feet. It's a fully metal lens... guess what, dented the aperture ring and now it's very hard to get it to stop down to f/8 and beyond...

Which one?
A friend of mine dropped his XT1 and 56mm/1.2 (in the bag). Only a short drop, first he tought no problem, later on he want to be sure and looke inside the bag - lens mount was ripped from the lens. And inside it was plastic he said.

I like metal very much. But I also know that plastic can be good:
I tested my DIY converted Canon FD 300mm/2.8L (2.3kg weight) on an old Canon EOS 500n camera - this camera has a plastic mount.
No problem holding the hole combination horizontal - and only holding the camera on the right hand grip.

ZoneV wrote in post #17020222
Which one?
A friend of mine dropped his XT1 and 56mm/1.2 (in the bag). Only a short drop, first he tought no problem, later on he want to be sure and looke inside the bag - lens mount was ripped from the lens. And inside it was plastic he said.

I like metal very much. But I also know that plastic can be good:
I tested my DIY converted Canon FD 300mm/2.8L (2.3kg weight) on an old Canon EOS 500n camera - this camera has a plastic mount.
No problem holding the hole combination horizontal - and only holding the camera on the right hand grip.

Almost all lenses have a plastic inner mount (underneath the part that actually connects to the camera). I believe it was lensrentals.com that had an article on this recently.

And this had nothing to do with the lens mount, it was my XF 35mm by itself, I dropped it while changing lenses and the aperture ring and metal hood were both dented and bent. Had they been plastic they likely would've absorbed the impact and then reformed to their original form. As corndog pointed out, metal often dents or cracks, plastic is more likely to flex and then hold it's original shape.

People often put far too much stock into how things feel and not enough into how they actually perform in real use. I shoot mostly with vintage lenses (note my sig) and all of those are metal, none of my plastic Canon lenses ever felt any more "cheap" to me (aside from the 50/1.8ii which feels very cheap) and as I said they were plenty durable.