Why does my DIY shaped bokeh mask show up as a black frame instead of shaping the blur?
Asked 5/1/2012
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2 answers
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I tried making a DIY shaped bokeh mask for a Micro Four Thirds camera, using the 14–42mm kit lens. At 14mm and f/3.5, I cut a small shape based on the lens opening, but instead of getting shaped bokeh highlights, the photo shows a mostly black frame with only a small shaped “window” in the center.
What causes this, and is it because I’m using a wide-angle kit zoom? Can shaped bokeh work with this lens at all, or does it really require a different focal length or a faster lens?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
5
At 14mm your field of view is too wide. You are looking at the shaped frame you have made rather than just through it. Most lenses that people use are 50mm and above, and a wide aperture of 2.8 or bigger. Whilst the long end of your zoom might not get the frame of your DIY kit in shot, the f stop won't be fast enough to create the bokeh effect you want.
This was previously asked here so take a look at what people said.
Also I just found this site which shows you how to calculate what sizes you'd need for your cut shapes etc with what focal lengths and apertures
And to answer your last question, you may get some amount of shaped bokeh if you experiment enough, but with such a 'slow' lens you are not going to get the kind of images given as examples in your link.
Originally by user3584. Source · Licensed CC BY-SA 4.0
user3584
14y ago
0
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Your mask is showing up because at 14mm the lens is so wide that the camera can actually see the edges of the mask itself. Instead of only affecting out-of-focus highlights, it becomes a visible frame in the image.
DIY shaped bokeh works best when the cutout is very close to the lens’s optical center and the lens has a relatively simple design. That’s why people usually have better results with longer, fast prime lenses (often 50mm or longer, with a wide aperture like f/2.8 or faster).
With your 14–42mm kit zoom, there are two problems:
- 14mm is too wide, so the mask enters the frame.
- f/3.5–5.6 is relatively slow, so the bokeh effect will be weak compared with the examples you’ve seen.
You might get a small effect by experimenting at the long end of the zoom, but this lens is not ideal for strong shaped bokeh. A longer focal length and wider maximum aperture will make the effect much easier.
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AI14y ago
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