aperture in photography (or how bokeh happens)

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

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

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Page 1: Aperture in Photography (or how bokeh happens)

Aperture in Photography

(Or how Bokeh happens?)

Guilherme Zühlke O’Connor

twitter.com/guioconnor

facebook.com/guioconnor

Page 2: Aperture in Photography (or how bokeh happens)

BOKEH? WTF?

Page 3: Aperture in Photography (or how bokeh happens)

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

directions

Page 4: Aperture in Photography (or how bokeh happens)

A Photo Camera is a device to single out an organised cone of

rays of light.

Page 5: Aperture in Photography (or how bokeh happens)

Ideally, an infinitesimally small hole would let in a single ray from each

point of the subject

Page 6: Aperture in Photography (or how bokeh happens)

In Practice the hole has dimensions and therefore multiple rays from

each point are projected.

Page 7: Aperture in Photography (or how bokeh happens)

Mutiple Rays from a single point

• Create multiple slightly displaced images of the same object

Page 8: Aperture in Photography (or how bokeh happens)

Mutiple Rays from a single point

• Create multiple slightly displaced images of the same object

• More rays of light coming in means more light

Page 9: Aperture in Photography (or how bokeh happens)

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.

Page 10: Aperture in Photography (or how bokeh happens)

But multiple images slightly displaced means you can’t single

any one out.

Page 11: Aperture in Photography (or how bokeh happens)

But multiple images slightly displaced means you can’t single

any one out.

That’s blur for ya!

Page 12: Aperture in Photography (or how bokeh happens)

…so cameras have lenses to make these multiple rays of light

converge into a single image

Page 13: Aperture in Photography (or how bokeh happens)

More Light, and no blur!

Page 14: Aperture in Photography (or how bokeh happens)

But wait!

What’s the bokeh again?

Page 15: Aperture in Photography (or how bokeh happens)

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

Page 16: Aperture in Photography (or how bokeh happens)

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

Page 17: Aperture in Photography (or how bokeh happens)

Well, it turns out that the lens can only make converge rays of light coming from given distance from the lens at a time.

Page 18: Aperture in Photography (or how bokeh happens)

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.

Page 19: Aperture in Photography (or how bokeh happens)

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

Page 20: Aperture in Photography (or how bokeh happens)

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

Page 21: Aperture in Photography (or how bokeh happens)

Let’s do the Math, shall we?

Page 22: Aperture in Photography (or how bokeh happens)

f-stops, the measurement of aperture.

f = Lens Focal Length / diameter of aperture

Page 23: Aperture in Photography (or how bokeh happens)

f-stops, the measurement of aperture.

f = Lens Focal Length / diameter of aperture

Focal length = 50mmDiameter = 12.5mm

f = 50 / 12.5= f/4

Page 24: Aperture in Photography (or how bokeh happens)

The incoming light is proportional to the area of the aperture.

Area = πr2

Page 25: Aperture in Photography (or how bokeh happens)

Focal length = 50mmDiameter = 35.7mmf = 50 / 35.7 = f/1.4

Focal length = 50mmDiameter = 12.5mm

f = 50 / 12.5 = f/4

Focal length = 50mmDiameter = 17.6mmf = 50 / 17.6 = f/2.8

Diameter X 1.4Area X 2Light X 2

Diameter X 2Area X 4

Light X 4 (*)

Page 26: Aperture in Photography (or how bokeh happens)

(*) And lots of bokeh!

Page 27: Aperture in Photography (or how bokeh happens)

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

?Questions?