Aperture in Photography (or how bokeh happens)

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Lightning talk about lenses, blur, bokeh and the fabulous world of f-stops.

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Aperture in Photography (or how bokeh happens)

  1. 1. Aperture in Photography<br />(Or how Bokeh happens?)<br />Guilherme Zühlke O’Connor<br />twitter.com/guioconnor<br />facebook.com/guioconnor<br />
  2. 2. Bokeh? WTF?<br />
  3. 3. When light hits an unpolished surface it spreads rays of light in all directions<br />
  4. 4. A Photo Camera is a device to single out an organised cone of rays of light.<br />
  5. 5. Ideally, an infinitesimally small hole would let in a single ray from each point of the subject<br />
  6. 6. In Practice the hole has dimensions and therefore multiple rays from each point are projected.<br />
  7. 7. Mutiple Rays from a single point<br />Create multiple slightly displaced images of the same object<br />
  8. 8. Mutiple Rays from a single point<br />Create multiple slightly displaced images of the same object<br />More rays of light coming in means more light<br />
  9. 9. Mutiple Rays from a single point<br />Create multiple slightly displaced images of the same object<br />More rays of light coming in means more light<br />Film (or sensors) depend on light to create images. The more light, the merrier.<br />
  10. 10. But multiple images slightly displaced means you can’t single any one out.<br />
  11. 11. But multiple images slightly displaced means you can’t single any one out.That’s blur for ya!<br />
  12. 12. …so cameras have lenses to make these multiple rays of light converge into a single image<br />
  13. 13. More Light, and no blur!<br />
  14. 14. But wait!What’s the bokeh again?<br />
  15. 15. In photography, bokeh is the blur or the aesthetic quality of the blur, in out-of-focus areas of an image, or "the way the lens renders out-of-focus points of light."<br />http://en.wikipedia.org/wiki/Bokeh<br />
  16. 16. http://www.flickr.com/photos/ashumittal/4940709917<br />
  17. 17. Well, it turns out that the lens can only make converge rays of light coming from given distance from the lens at a time.<br />
  18. 18. Well, it turns out that the lens can only make converge rays of light coming from given distance from the lens at a time.<br />This means if you adjust the lens to focus at one point. Objects will be progressively more blurred the further or nearer they are.<br />
  19. 19. The wider the aperture, the more blurred your bokeh will be.<br />
  20. 20. But also the more light reaches the sensor or film, which means faster shots and higher definition.<br />
  21. 21. Let’s do the Math, shall we?<br />
  22. 22. f-stops, the measurement of aperture.<br />f = Lens Focal Length / diameter of aperture<br />
  23. 23. f-stops, the measurement of aperture.<br />f = Lens Focal Length / diameter of aperture<br />Focal length = 50mm<br />Diameter = 12.5mm<br />f = 50 / 12.5= f/4<br />
  24. 24. The incoming light is proportional to the area of the aperture.<br />Area = πr2<br />
  25. 25. Focal length = 50mm<br />Diameter = 12.5mm<br />f = 50 / 12.5 = f/4<br />Focal length = 50mm<br />Diameter = 17.6mm<br />f = 50 / 17.6 = f/2.8<br />Diameter X 1.4<br />Area X 2<br />Light X 2<br />Focal length = 50mm<br />Diameter = 35.7mm<br />f = 50 / 35.7 = f/1.4<br />Diameter X 2<br />Area X 4<br />Light X 4 (*)<br />
  26. 26. (*) And lots of bokeh!<br />
  27. 27. ?<br />Questions?<br />Further reading:<br />http://www.z-oc.com/blog/2007/08/understanding-cameras-and-photography/<br />

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