Which words spring to mind when you think about 70-200mm zoom lenses - solid and dependable or fragile and unreliable? Lensrentals' Roger Cicala has just published an analysis of the failure rates of the 12,000 lenses he rents out, and the results may surprise you. Even having taken into account popularity and accidental damage, five 70-200s turn up in his highest failure rate table - including the latest models from Canon and Nikon.

As always with Roger's work, we'd recommend reading his entire article before commenting - partly because he openly discusses the inherent weaknesses and gaps of his analyses, but mainly because it's really interesting.

A picture of complexity - between the optics and the case of this Canon 70-200mm you'll find gearing to reverse the movement of turning the zoom ring, along with a small screw for adjusting the tilt of one of the lens elements - as well as all the electronics and motors you might expect. Picture courtesy of Lensrentals

Even having removed instances of the lenses being damaged, Cicala found the Nikon 70-200mm F2.8 VR II, Sigma 70-200mm F2.8 OS, Canon 70-200mm F2.8 IS II, 70-200mm F4 IS and Sony 70-200mm F2.8 to be amongst the eighteen lenses that last the least amount of rental weeks between requiring servicing. Indeed all of them needed repairing nearly twice as often as the average lens (which would last for a little over 100 rental weeks between services).

So why is it these reputedly 'bomb-proof' workhorses need constant maintenance? A closer look at the Lensrentals figures sheds a little light on some specifics - 40% of failures of the Nikkor come from jammed zoom mechanisms, while all the Sonys suffered from AF motor failures, suggesting some of the problems stem from specific design flaws.

A close-up of that adjustment screw - just one of many widgets-per-cubic-centimeter typical in a 70-200mm lens. Picture courtesy of Lensrentals

We spoke to Cicala, wondering whether it was their very reputation for durability that was the 70-200's undoing. 'I think that's part of it' he agrees: 'they tend to be hard-use lenses, with sporting events and action shooting being the order of the day.'

We also wondered whether it was a consequence of shipping such large, heavy lenses around - something Cicala had also considered: 'they are heavy and when they bang into a table, hanging from a neck strap, or get dropped during shipping, that's a lot of momentum jarring the insides.'

But there's more to it than this, he suggests: 'supertelephoto primes are also heavy and get shipped just as much but they hardly ever fail. This could be because they tend to be monopod or tripod mounted, and people baby them (they're aware that dropping a rented 600mm f/4 IS would cost a fortune), but I don't think that explains the whole difference.'

The final factor, he says, is complexity: 'When we disassemble any of the 70-200 F2.8s, the insides are exceedingly robust and well put together, but they're also probably the most complex as far as widgets-per-cubic centimeter of any lens. The supertele primes aren't nearly as jam-packed - there's a lot more space between components, usually.'

So, while Cicala's data doesn't allow us to pin-down precisely why his 70-200s keep failing, it's something worth considering, before you consider actually trying to use your 70-200mm to hammer nails in.