I regularly carry a back pack around the world which contains three DSLR cameras, three lenses of various sizes, lens cleaning tools, batteries, flash, chargers and a number of leads. The back pack fits Ryanair cabin bag size rules,as I have to use them sometimes, and weighs just under 7kgs which more and more airlines are now imposing for cabin bags.
The reaction of security around the world is interesting. Irish airports sometimes ask me to open it after x-ray, in Australia, New Zealand, Singapore, Hong Kong, Brazil it normally just goes through without comment. Some US airports ask for it to be opened and some UK and European airports ask for the bag to be opened. Whenever it is opened a cursory examination usually follows.
I have had two exceptions, both in the UK, one acceptable if over zealous, the other totally objectionable. The first was at Aberdeen some years ago when I was politely taken aside and the contents of the bag were swabbed for explosive traces. The second was last year at T5 Heathrow when the bag was spotted prior to x-ray on the belt by a young total jobsworth who introduced himself by saying "that bag is too big and heavy for cabin baggage". When I pointed out its size and weight and that it had been through T5 security dozens of times without incident, he made me completely empty every last item into 4 trays stating that camera lenses don't show up properly in x-ray machines. Delaying the already long queue I then delayed it longer by slowly and carefully repacking the items as close to the machine as possible as I wanted to keep everything in reach and view as the total value of the bag's contents is in excess of £4000.
The supervisor and I then fell out as she wanted me to move the trays off the shelf. Given that there were two other trays belonging to me containing shoes, belt, wallet, passport, change, jacket and phone, I asked for help which she refused. I stood my ground and stayed where I was until I had repacked and got my other belongings back where they should be. I then complained about having to unpack the bag and was replied to with a shrug of the shoulders.
I have no problem with inconsistent levels of scanning or having the bag hand checked after x-ray, on one side from the main line, but the attitude that day, the lie about lenses and x-ray machines and the attitude of the supervisor unfortunately highlights the standard of security employees at Heathrow and Gatwick which, given their regular attitude to passengers, this example apart, seem to have garnered the most obnoxious staff I've come across anywhere.