Lenses and focal length

Things have been getting pretty technical around here recently - lots of exercises to get a better understanding of how things (i.e. my kit) work. Here is Fran helping me get a better idea of how lenses and different focal lengths really function.

 1. 1/60, f2.8, 17mm. This is the shortest focal length and so the widest angle on my favourite Canon telephoto zoom. I've shot Fran so that his waist is at the bottom of the shot and there is around a hand's distance above his head.

 2. 1/50, f2.8, 20mm. The idea is to get the same shot - from the waist to a hand above Fran's head - but by working my way through the focal lengths. I take a step back to get this.

 3. 1/60,  f2.8, 28mm. So each time the focal length changes, to keep the same shot I have to move backwards away from Fran.

 4. 1/60, f2.8, 35mm. It is the opposite of what often happens: I can remain in the same spot and as the zoom moves (changing the focal length) it transforms the shot.

 5. As above, 55mm. The longest focal length of my zoom. The difference that the lens and the FL makes to the subject and to the background becomes clear in these shots - Fran at 17mm looks very different to Fran at 55mm, and so does the corridor.

 6. 1/80, f2.8, 50mm. This is a bit of an anomaly - my 50mm lens is EF and so designed for a full-frame sensor/35mm film. It increases the effective focal length on my cameras APS-C size sensor to approx 80mm. There is a link to some notes on this below.

 7. 1/50, f4.0, 70mm. A bigger zoom lens, and perspective is really beginning to get compressed.

 8. 1/80, f4.0, 100mm. The background view that I started with is disappearing fast. I'm a long way away from Fran now, and still moving back for each shot. I am doing the legwork that a zoom lens usually does for you.

 9. 1/50, f4.5, 135mm.

 10. 1/40, f4.5, 180mm. By now I'm at the other end of the corridor. The shutter speeds get slower as the maximum aperture gets higher...

11. 1/30, f5.6, 300mm. ...and this makes camera shake inevitable, particularly hand holding a big telephoto lens. The corridor background has almost completely disappeared and the subject is isolated.

So that is an insight into just what the different focal lengths are doing - not only showing more or less of a scene, but making subtle but distinct differences to the image itself.

 These are my two lenses, not to scale. And below is a telephoto lens (similar FL's to Fran's) that I would very much like to possess!

 A big thank you to Fran for his patience and the use of his lens. Hope to see you soon if you read this! Here's the link to some notes on sensor sizes from one of our sessions:
Sensors and Lenses PDF