{"id":30234,"date":"2021-12-08T19:17:08","date_gmt":"2021-12-08T18:17:08","guid":{"rendered":"https:\/\/phillipreeve.net\/blog\/?p=30234"},"modified":"2023-10-30T11:12:32","modified_gmt":"2023-10-30T10:12:32","slug":"bokeh-explained","status":"publish","type":"post","link":"https:\/\/phillipreeve.net\/blog\/bokeh-explained\/","title":{"rendered":"Bokeh Explained"},"content":{"rendered":"

Introduction<\/h2>\n
\"ttartisan
Leica M10 | TTArtisan 50mm 1.4 | f\/1.4<\/figcaption><\/figure>\n

The bokeh quality – or a lens’ rendering for that matter – is probably one of the most discussed and maybe also most important aspects of a (fast) lens. While many people think only the focal length and the maximum aperture are important, there is actually much more to it, as I will try to show you in this article. This knowledge may also aid you in finding the best lens for your specific needs.<\/p>\n

\"Sony
Sony A7rII | MS-Optics Aporis 135mm 2.4 | f\/2.4<\/figcaption><\/figure>\n

There are two main things to consider here: bokeh quantity and bokeh quality, which we will both have a look at.<\/p>\n

<\/p>\n

I will mostly be talking about background bokeh here though, as foreground bokeh is more of a niche application and might also overcomplicate this article. I will also not talk about local pixel level adjustments to alter the bokeh rendering.
\n<\/em><\/p>\n\n

Quantity<\/h2>\n
\"zhong
Sony A7III | Zhong Yi 135mm 1.4 | f\/1.4<\/figcaption><\/figure>\n

The quantity of the bokeh depends not only on the lens’ specifications or the distance relations in the scene, but also on the optical vignetting and field curvature characteristics of a given lens.<\/p>\n

Maximum Aperture and Focal Length<\/h3>\n

What is a fast lens? A 50mm lens with a maximum aperture of f\/0.95 probably is, same goes for an 85mm f\/1.4 lens. Now a 35mm f\/2.8 most people wouldn’t consider fast whereas a 400mm f\/2.8 is considered a very fast tele lens, despite both having a maximum aperture of f\/2.8.<\/p>\n

\"canon
Sony A7III | Canon EF 200mm 2.0 L IS | f\/2.0<\/figcaption><\/figure>\n

What becomes obvious here: focal length and maximum aperture are both equally important<\/strong> and if you divide focal length<\/em> by maximum aperture<\/em> you get the size of the entrance pupil<\/em>, which is a good reference point to evaluate the “blur potential”<\/em> of a certain lens. Bigger is generally better here, I already talked about this in my article about Brenizer\/Bokehpanorama<\/a>, so maybe have a look there if you are curious what lenses to use in order to achieve the highest “quantity” of bokeh in your pictures.<\/p>\n

\"olympus
Sony A7rII | Olympus OM 250mm 2.0 Zuiko | f\/2.0<\/figcaption><\/figure>\n

The take away message from this section: all else equal a faster lens of the same focal length will (or should<\/em>, see “optical vignetting” section) yield more blur and a longer lens with the same maximum aperture will also yield more blur (you need to adjust the distance to your subject for similar framing though).<\/p>\n

I guess most of you were already aware of this \ud83d\ude42<\/p>\n

Distance Relations<\/h3>\n

What is actually more important than the lens you use are the distance relations in the scene. To get the highest amount of blur your subject should be as close to the camera as possible and the background should be as far behind the subject as possible<\/strong>.<\/p>\n

These three pictures have all been taken with the Laowa 35mm 0.95<\/a> set to f\/0.95. In the first picture I am close to the woman, the background is blurred noticeably. In the second picture I am farther away from the woman, the background is still a bit out of focus.
\nNow in the third picture the distance to the woman is similar to that in the second picture, but that background is much closer and at this output size you can hardly tell it is out of focus at all.<\/p>\n