Aperture refers to the size of the opening in a camera lens through which light passes. A small aperture opening (higher f-stop number) results in greater depth of field with less blurry backgrounds, known as bokeh. A large aperture opening (lower f-stop number) allows more light into the camera but results in shallower depth of field and more blurred out-of-focus areas, creating bokeh effects. The size of the aperture opening affects the amount of light reaching the sensor or film, with a larger opening admitting more light and allowing faster shutter speeds or lower ISO settings.

1. Aperture in Photography (Or how Bokeh happens?) Guilherme Zühlke O’Connor twitter.com/guioconnor facebook.com/guioconnor

2. Bokeh? WTF?

3. When light hits an unpolished surface it spreads rays of light in all directions

4. A Photo Camera is a device to single out an organised cone of rays of light.

5. Ideally, an infinitesimally small hole would let in a single ray from each point of the subject

6. In Practice the hole has dimensions and therefore multiple rays from each point are projected.

7. Mutiple Rays from a single point Create multiple slightly displaced images of the same object

8. Mutiple Rays from a single point Create multiple slightly displaced images of the same object More rays of light coming in means more light

9. Mutiple Rays from a single point Create multiple slightly displaced images of the same object More rays of light coming in means more light Film (or sensors) depend on light to create images. The more light, the merrier.

10. But multiple images slightly displaced means you can’t single any one out.

11. But multiple images slightly displaced means you can’t single any one out.That’s blur for ya!

12. …so cameras have lenses to make these multiple rays of light converge into a single image

13. More Light, and no blur!

14. But wait!What’s the bokeh again?

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." http://en.wikipedia.org/wiki/Bokeh

16. http://www.flickr.com/photos/ashumittal/4940709917

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.

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. This means if you adjust the lens to focus at one point. Objects will be progressively more blurred the further or nearer they are.

19. The wider the aperture, the more blurred your bokeh will be.

20. But also the more light reaches the sensor or film, which means faster shots and higher definition.

21. Let’s do the Math, shall we?

22. f-stops, the measurement of aperture. f = Lens Focal Length / diameter of aperture

23. f-stops, the measurement of aperture. f = Lens Focal Length / diameter of aperture Focal length = 50mm Diameter = 12.5mm f = 50 / 12.5= f/4

24. The incoming light is proportional to the area of the aperture. Area = πr2

25. Focal length = 50mm Diameter = 12.5mm f = 50 / 12.5 = f/4 Focal length = 50mm Diameter = 17.6mm f = 50 / 17.6 = f/2.8 Diameter X 1.4 Area X 2 Light X 2 Focal length = 50mm Diameter = 35.7mm f = 50 / 35.7 = f/1.4 Diameter X 2 Area X 4 Light X 4 (*)

26. (*) And lots of bokeh!

27. ? Questions? Further reading: http://www.z-oc.com/blog/2007/08/understanding-cameras-and-photography/