Canon 100-400 Mk II users - ET-83D lens hood design flaw?

[StewartR]

At Lenses For Hire we have about 20 copies of the Canon 100-400 Mk II, and we've been astonished at the high breakage rate of the lens hoods. We've had about nine of them break in the last month or so, always in exactly the same way. We think we can see how and why it's happening, and we believe it is a design flaw. I'm trying to get Canon to take it seriously. So if anybody else out there has experienced this, I'd like to know.

Here's a photo of the ET-83D hood. Just inside the rim of the hood there is a relatively complicated assembly which attaches the hood to the lens; I've crudely highlighted it in yellow. This assembly is attached to the main part of the hood using four small screws; I've highlighted them in green.



The design flaw is that the yellow assembly is mounted inside the main part of the hood. This means that, if the front edge of the hood takes a knock whilst the hood is mounted on the lens, the force tends to separate the yellow assembly from the main part of the hood. The four green screws are too flimsy to hold the thing together in these circumstances, so they get ripped out and the hood comes apart. The yellow bit stays attached to the lens and the main part comes off.

Of course, by their very nature lens hoods, and especially those fitted to large telephoto lenses, do tend to take knocks in exactly this way That's exactly what we've seen every time. The green screws rip out and the hood comes apart in two pieces, the yellow bit and the rest.

Has anyone else experienced this?

 

[RacingSnake]

I can't say I have, but mine took a big knock the other day, all stayed intact (thankfully).
(what's the sliding hatch bit for on the hood?)

 

[Sharky]

(what's the sliding hatch bit for on the hood?)

For rotating CPL filters with the hood attached.

 

[HoppyUK]

Nine breakages in one month?! How much evidence does Canon need? Luckily, replacement hoods are only £55

It's hard to tell from the picture, but it's not clear how mounting the yellow bit outside would make much difference. The knock/leverage applied to the screws would be the same, and that's the weak point. It needs more/stronger screws and a dollop of glue.

 

[StewartR]

It's hard to tell from the picture, but it's not clear how mounting the yellow bit outside would make much difference. The knock/leverage applied to the screws would be the same, and that's the weak point. It needs more/stronger screws and a dollop of glue.

I don't think so.

Consider the scenario where the hood is mounted on the lens and it sustains a blow to the front of the hood, aimed towards the camera. Or, equivalently, imagine that you're putting the lens down vertically, with the hood mounted and pointed downwards, and you put it down a bit too hard. In both cases the force which is transmitted into the hood acts to rip out the green screws. The main part of the hood is being pushed towards the back of the lens, the yellow bit is held securely in place, and - because the yellow bit is mounted on the inside of the lens - only the four green screws are holding it together.

But if the yellow bit were mounted outside the main part of the hood, a similar blow would push the two components together rather than act to separate them.

 

[HoppyUK]

I see what you're saying, but it's very unlikely to be hit square-on. It's going to take a blow to one side or other, top or bottom, and that will stress one of the screws far more than the others regardless - either the nearest screw, or the one directly opposite.

If this is a widespread problem - seems like it, unless all your lenses were purchased together from a duff batch - then Canon will quietly fix it, if they haven't already. Lenses get small and mostly invisible upgrades all the time, never announced, mostly I believe to improve quality control issues with refinements to the internal assembly.

 

[Ziploc]

Had this happen to mine and only from a slight knock. Think it is a screw torque up problem.

 

[arthurbikemad]

Humm maybe not stand mine on the hood any more, but I will prob forget haha, well if mine brakes it will be getting glued back on solid, mind you with my OCD I doubt that.. still if it brakes I know where to post, thanks for the heads up.

 

[LC2]

Is it possibly meant to be sacrificial? Designed to break rather than transmit a shock to the lens itself?

 

[HoppyUK]

The ET-83C lens hood fits, from the 100-400L Mk1. It's almost identical in size, just 3mm longer - doesn't vignette on the 100-400L Mk2 though.

 

[George]

Interesting point, Stewart, think I'll stop standing mine on the hood!!

Will WEX (I seem to remember that's where you bought them from) replace under warranty?

George.

 

[arthurbikemad]

I note a number of L lens's share the same hood design, i.e 24-70Mk2, 70-200Mk2 and I bet a good few others.

 

[Nod]

Is it possibly meant to be sacrificial? Designed to break rather than transmit a shock to the lens itself?

This would be my guess as well, much the same as crumple zones in cars are designed to keep as much of the impact shock away from the occupants. Better a £55 (gulp!) hood than an even more expensive internal repair.