\n
<\/p>\n <\/p>\n <\/p>\n Bokeh is an approximation of the sound of a Japanese word – there is no equivalent word in English.<\/span><\/p>\n <\/p>\n It refers to the quality of the out-of-focus areas of an image.<\/span><\/p>\n<\/div>\n <\/p>\n You probably thought that one out-of-focus image was much like another, but it is not. The appearance of the\u00a0out-of-focus image can be very distinctive, and can add to or detract from the effectiveness of the image.<\/span><\/p>\n<\/div>\n <\/p>\n Bokeh is big in Japan, where some photo magazines include the results in lens test alongside other performancecriteria. The problem is that bokeh is – at the moment – purely subjective. No one has yet come up with a reliablemethod of measuring the effect, and translating this into a quality index. It is also very difficult to describe in words.<\/span><\/p>\n<\/div>\n German lenses are praised for good bokeh, while many Japanese lenses, even from major manufacturers, are not\u00a0well regarded. Canon lenses seem to be an exception, and Canon uses good bokeh as a selling point in some of its\u00a0Japanese adverts. In particular, the EF 35mm f2 and EF 100mm f2.8 have good reputation in this respect.<\/p>\n<\/div>\n It is unlikely that bokeh will ever replace sharpness as the main selling point of a lens, but certainly influences\u00a0our impression of lens performance.<\/p>\n<\/div>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n Above: To understand bokeh, you need to know how a lens forms an image. In<\/span><\/p>\n<\/div>\n <\/p>\n simple term, rays of light from a point on an in-focus subject pass through the\u00a0lens and come together at a point on the film surface. This is repeated for all the\u00a0other points at the same distance from the lens.<\/span><\/p>\n<\/div>\n <\/p>\n <\/p>\n<\/div>\n <\/p>\n <\/p>\n <\/p>\n That, at least, is the theory. In practice, no lens is perfect and the out-of-focus area is more likely to be\u00a0an ellipse than a circle (top shape). Alternatively, it\u00a0may take on some of the characteristics of the lens aperture and be a polygon – possibly with an irregular shape (bottom shape):<\/p>\n <\/p>\n Also, the tonal range across the shape may not be even. It can fade towards the edge\u00a0<\/span>(below left), or the centre (below centre), or from one side to the other (below right):\u00a0<\/span><\/p>\n<\/div>\n <\/p>\n<\/div>\n <\/p>\n The causes of these variations are the usual lens aberrations – coma, spherical\u00a0<\/span>aberration and chromatic aberration. These aberrations vary within a single lens\u00a0<\/span>element, and are usually greater towards the edges, so bokeh may also vary\u00a0<\/span>across the image. In extreme cases, a thin out-of-focus line might even become\u00a0<\/span>two parallel lines.<\/span><\/p>\n<\/div>\n “Good” bokeh seems to come from lenses which produce circular, smooth-toned\u00a0<\/span>out-of-focus shapes across the film. There is nothing you can do to alter the\u00a0<\/span>bokeh of an existing lens, though you may find it changes at different aperture\u00a0<\/span>settings.<\/span><\/p>\n<\/div>\n \u00a0<\/span><\/p>\n<\/div>\n Bokeh for beginners (Pubblished in one of my old site, on 1998 – From EOS Magazine – March 1998) Clicca qui per la versione in italiano. There’s a new word entering the language of photography – and its meaning is unclear! It is relatively easy to decide whether or not a lens … Continue reading Bokeh for beginners<\/span> ![\"](\"https:\/\/images-blogger-opensocial.googleusercontent.com\/gadgets\/proxy?url=http%3A%2F%2F1.bp.blogspot.com%2F-W3xkPLn0no4%2FUxCPNKLmnII%2FAAAAAAAB1zc%2F75YxxDM7v3U%2Fs1600%2Fit.gif&container=blogger&gadget=a&rewriteMime=image%2F*\")
Clicca qui per la versione in italiano.<\/a><\/p>\n
\nThere’s a new word entering the language of photography – and its meaning is unclear!<\/h3>\n
<\/h3>\n
It is relatively easy to decide whether or not a lens offers good sharpness.
\nBut how do you define its performance with out-of-focus images ? And does it matter ?
\nWell, it does to Japanese photographers, and they have a word for it – ‘bokeh’.<\/h4>\nThe theory behind bokeh<\/h4>\n
\n![\"\"](\"https:\/\/images-blogger-opensocial.googleusercontent.com\/gadgets\/proxy?url=http%3A%2F%2F3.bp.blogspot.com%2F-bRb4D92OyWY%2FUxBlqH4P6_I%2FAAAAAAAB1xk%2FLMvB5Il2M_s%2Fs1600%2Fbokeh1.gif&container=blogger&gadget=a&rewriteMime=image%2F*\")
<\/a><\/p>\n![\"\"](\"https:\/\/images-blogger-opensocial.googleusercontent.com\/gadgets\/proxy?url=http%3A%2F%2F4.bp.blogspot.com%2F-YWxfMC5LoYQ%2FUxBl6Yg1wEI%2FAAAAAAAB1xs%2F3eY2Dr9_tYI%2Fs1600%2Fbokeh2.gif&container=blogger&gadget=a&rewriteMime=image%2F*\")
<\/a><\/p>\n![\"\"](\"https:\/\/images-blogger-opensocial.googleusercontent.com\/gadgets\/proxy?url=http%3A%2F%2F2.bp.blogspot.com%2F-zWvG3bDgQho%2FUxBmDSLdf2I%2FAAAAAAAB1x0%2FS7R-tWpe-aE%2Fs1600%2Fbokeh3.gif&container=blogger&gadget=a&rewriteMime=image%2F*\")
<\/a><\/p>\n![\"\"](\"https:\/\/images-blogger-opensocial.googleusercontent.com\/gadgets\/proxy?url=http%3A%2F%2F4.bp.blogspot.com%2F-akU-pXAiN3I%2FUxBmRG3UBkI%2FAAAAAAAB1x8%2Fh1Lu1f2ZFdk%2Fs1600%2Fbokeh4.gif&container=blogger&gadget=a&rewriteMime=image%2F*\")
<\/a>Above: Rays of light from parts of the scene which are not in focus come\u00a0together at a point in front of or behind the film. When this out-of-focus beam hits\u00a0the film, it is a small circle (white area on diagram), rather than a point of light.<\/span><\/p>\n![\"\"](\"https:\/\/images-blogger-opensocial.googleusercontent.com\/gadgets\/proxy?url=http%3A%2F%2F2.bp.blogspot.com%2F-jUs7OCCdvOU%2FUxBmbvRA0rI%2FAAAAAAAB1yE%2FO9fb8KXgr88%2Fs1600%2Fbokeh5.gif&container=blogger&gadget=a&rewriteMime=image%2F*\")
<\/a><\/p>\n