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photo:bokeh

bokeh

see also:

introduction

  • bokeh is the subjective aesthetic quality of the appearance of out of focus highlights (OOFHs) in a photographic image
  • as it is largely dependent upon the spherical aberration characteristics of a lens, the foreground bokeh is usually quite different to background bokeh for a given lens.
  • factors which affect bokeh:
    • spherical aberration determines how evenly the light is distributed within the OOFHs with lenses with busy looking OOFHs (poor bokeh) having OOFHs with strong peripheral double contours instead of a single contour
    • shape of the aperture diaphragm partly determines shape of the OOFHs
    • mirror lenses have a central obstruction (the secondary mirror) which causes characteristic donut shaped OOFHs
    • optical vignetting may also create oval shaped OOFHs (Cat's eye effect) in the peripheries which can produce a rotatory effect with the ovals being aligned in a circular manner around the centre of the image - this is particular likely in certain lenses at wide apertures and short focal lengths but is even present on 85mm f/1.2 lenses
    • clipping of OOFHs by internal obstructions such as a mirror chamber that is too small
    • transverse CA may cause colour fringing of OOFHs with magenta on one side and green on the other side of the OOFH
    • longitudinal CA may cause colour in the OOFHs
    • astigmatism may distort the OOFHs and give oval shaped OOFHs pointing towards the centre

lenses known for their smooth background bokeh

some of my photos demonstrating bokeh qualities of various lenses

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set

photo/bokeh.txt · Last modified: 2014/05/05 09:59 by gary1