Now when I said a lens with faster aperture will always yield more blur then a slower lens with the same focal length this is true for the center of the frame, but the corners can be a different story, as there is this thing called optical vignetting. Optical Vignetting Leica M10 | Voigtlander VM 75mm 1.5 | f/1.5 The following aspects can not be simulated there though. To visualize what I have written in the past two sections you can also use a Depth of Field Simulator. How important the focus distance is also becomes very apparent when using macro lenses, at high magnifications – even when you stop down the lens a lot – the depth of field is thin as paper: Sony A7III | Laowa 85mm 5.6 Macro | f/11 Now 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. In the second picture I am farther away from the woman, the background is still a bit out of focus. In the first picture I am close to the woman, the background is blurred noticeably. These three pictures have all been taken with the Laowa 35mm 0.95 set to f/0.95. 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. What is actually more important than the lens you use are the distance relations in the scene. I guess most of you were already aware of this 🙂 Distance Relations The take away message from this section: all else equal a faster lens of the same focal length will (or should, 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). Sony A7rII | Olympus OM 250mm 2.0 Zuiko | f/2.0 Bigger is generally better here, I already talked about this in my article about Brenizer/Bokehpanorama, 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. What becomes obvious here: focal length and maximum aperture are both equally important and if you divide focal length by maximum aperture you get the size of the entrance pupil, which is a good reference point to evaluate the “blur potential” of a certain lens. Sony A7III | Canon EF 200mm 2.0 L IS | f/2.0 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. 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. 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. Quantity Sony A7III | Zhong Yi 135mm 1.4 | f/1.4
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