November challenge; friday 50.

In the olden days when TV consisted of just two channels, Big Brother was a rather sinister idea in a George Orwell novel and going out to dinner meant prawn cocktail, steak (or plaice) with chips and peas, followed by black forest gateau and an Irish Coffee at a Berni Inn - all for the princely sum of 10 shillings and 6 pence - your 35mm film camera would more than likely come with a 50mm lens fitted as standard. Hence the label ‘standard lens’. Anything with a shorter focal length would be called ‘wide angle’ and anything longer would be ‘telephoto’.

The holy trinity for the serious amateur was a 50mm lens, a 35mm lens and a 135mm lens. Anything longer or wider was considered both expensive and exotic. You’ll notice I’ve not mentioned zoom lenses. Although widespread in film and television, they didn’t really take off in still photography until your meal at the Berni Inn required payment in decimal currency.

The choice of 50mm as ‘standard’ for 35mm film was not arbitrary; it’s very similar to the perspective and field of view experienced by the human eye when focussed straight ahead. Either side of this, lenses and eyes part company. You can easily test this; if you photograph a building with a wide angle lens the verticals will start to converge - the building appears to fall backwards. But it doesn’t when you simply look at it. Similarly, when you shoot with a telephoto lens, distance is compressed - but not to your eyes.

Things got a lot more complicated when digital came along; suddenly sensors were all sorts of sizes, everyone had zoom lenses and so no one really knew what a standard lens was any more. Or cared. But I guess Chantler does because she wants you to use a 50mm lens for this challenge. Or whatever focal length gives the same sort of perspective on your camera.

Without doing loads of techie stuff, my camera has a sensor which is half the size of a film camera. Half the size means half the field of view - and so to keep the same perspective as the human eye, the focal length has to be halved as well.

This my old Nikkormat film camera, fitted with a 50mm standard lens. Taken with a micro 4/3rds format camera with 25mm standard lens.