Tündi Heveli
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Light in Photography - The aesthetic of background blur
Tünde Heveli, Bournemouth University, MA Digital Effects
Research Aims
Photography is the art of creating permanent images by recording light, and it also functions as reference for recreating accurate details in digital arts. The research will look at the background blur called bokeh. The aim is to discover whether bokeh is a controllable effect or not.
Materials and Methods
The research was done through studying visual and written materials. The gained information was then applied to a photography experiment.
Results
Aperture is responsible for contracting or expanding the opening of the lens’s diaphragm, therefore it is controlling the amount of light entering the body. It is measured in f-stops. When the hole lets less light to the sensors the focusing area gets smaller and the background gets blurred out. This naturally drives the eye on what is sharp (Barnbaum 2010).
Lens Aperture Chart (Cox 2015)
Bokeh is the aesthetic quality of the out of focus parts of the image rendered by the lens. Different lenses render bokeh differently due to unique optical designs (Gill 2015).
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Spherical aberration has a profound effect on bokeh. It is an image imperfection due to the spherical lens shape. Longitudinal chromatic aberration adds a red or green edge to blur (Travnik ca. 2016, Warlee 2015).
Spherical aberration (Travnik ca. 2016)
The shape of the bokeh can be controlled by placing black paper with a cut out whole in front of the lens. The blur will adapt the shape of the hole. The left image shows the original bokeh of the Canon 100 mm lens, the right image used a custom shape to create the effect. The experiment also discovered that moving the cut out shape in front of the lens makes the object appear in 3D space.
The aim of the experiment was to observe the aesthetic of the bokeh using different lenses. In order to compare how the lenses render the blur, a series of photographs were taken on the same settings.
The difference is evident between each image. The 70-200 mm lens has a smooth blur, while the 50 mm lens has a more distractive effect. Faster lenses produce more pleasing bokeh.
The above example shows the quality of the bokeh between the f-stop ranges.
Conclusion
The research reveals that the aesthetic of the background blur is a controllable effect. Understanding how the camera works and how to control aperture is vital. Fast lenses with an aperture of 2.8 or higher create a smooth bokeh, separating the object from the background. The shape of the blur is determined by the lens but it can be changed. One has to be careful with bokeh as it can also be distractive.
The research is important in the context of creating photorealistic visual effects. The success of a shot is in the details and the details are based on real world physics and references. Understanding bokeh could be vital for creating a visually appealing photorealistic shot.
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References
Barnbaum, B., 2010. The Art of Photography. An Approach to Personal Expression. Santa Barbara, CA: Rocky Nook Publishing.
Busch, D., 2008. David Busch's Quick Snap Guide to Using Digital SLR Lenses [online]. Boston, MA: Course PTR.
Cox, S., 2015. Lens Aperture Chart [chart]. Available from: https://photographylife.com/lens-aperture-chart [Accessed 20 May 206].
Gill, H., 2015. Understanding lens terminology – Part 2 – Bokeh [online]. Available from: http://www.35mmc.com/28/05/2015/lens-terminology-sharpness-contrast-and-flare/ [Accessed 18 may 2016].
Travnik, J. ca 2016. On Bokeh [online]. Available from: http://jtra.cz/stuff/essays/bokeh/ [Accessed 23 May 2016].
Walree, P. 2015. Spherical aberration [online]. Available from: http://toothwalker.org/optics/spherical.html [Accessed 20 May 2016].