Introduction: Making a Bokeh Kit Using a 3D Printer

About: Raji Balakrishnan

Bokeh is a photographing technique of blurring the background to get interesting effects from the lights in the background. Bokehmeans appearance or feel of out of focus areas of an image.  The highlights on the points of lights are usually circles or polygons depending on the blur. We can change the shapes of these highlights by building our own filters and using them over the camera lenses.

There are a lot of DIY articles describing how to make these filters with paper and tape. When I came across these articles, as an amateur trying to learn photography I tried to make the filter caps with paper securing it with tape and rubber band around the lens. But I got tired quickly with the experiments because they were not easy to use and not convenient to carry them outdoors. So I decided to build the filters using 3D printing. These plastic bokeh filters are convenient to carry around in a pouch and much easier to use. You will have them handy to use anywhere and you can have interesting shots at events like birthday parties, graduation, portraits, night life.

Step 1: What You Need

1. The right lens - in general, lens with large aperture. I used my Canon Digital Rebel T1i with a Canon 50mm f/1.8 lens. Please refer to photography articles for more details on the lenses.
2. Inkscape - SVG graphics editor
3. Alibre or your choice of software for making the 3D design.
4. Access to 3D printer
5. Christmas lights or candles or small points of lights.

Step 2: Overview

There are two parts to the bokeh lens kit. 
1. The bokeh filter lens cap. - Custom lens cap to insert the bokeh filter discs.
2. The bokeh filter discs -  Circular discs with various shapes cut out .These discs are inserted in the filter lens cap.

Step 3: Bokeh Filter Shapes

Inkscape is a good option to make vector designs and is also open source.  Using inkscape, make shapes like heart, sun, clover or any design you like and save it in dxf format. The dxf format is convenient to import into Alibre for designing the 3D Model.  Select the size of the design based on the aperture requirements for your lens.  The maximum size of the design is calculated as the focal length of the lens (50mm in my case)  divided by the aperture of the lens(1.8mm in my case) which is 27.7mm. That will be the biggest hole for the designs possible and still be effective. The designs were made of diameter 28mm. It is important to scale the figure to 20mm x 20mm in inkscape itself, because it will be harder to do so after it has been imported into Alibre.

Step 4: Design Bokeh Filter Caps

The next step is to design a camera lens cap that would go over your camera lens. I used Alibre  to make the 3D design.  
1. Measure the diameter of the front of the lens or the existing lens cap. The diameter of the Canon 50mm lens that I used was 52mm.
2. The size of the cap that we are going to design now will be 52mm and height 2mm.
3. Make a slot of 29mm diameter in the center of the cap.  
4. Make provisions around the slot for inserting circular discs of 30mm diameter.

Step 5: Design the Bokeh Inserts

Design circular discs of 30mm diameter and height 2mm and for each design, import it from dxf to Alibre native format, then place it onto one of the sides of the disc and then cutoff the plastic based on that figure. These are the inserts that will go in the center of the lens cap designed in the previous step.  Design the circular discs with various designs.  Also design a plain circular one that will cover the slot completely when not in use.

Step 6: 3D Print

Print the lens caps and the bokeh inserts using a 3D printer. They come out of the printer white, but it is preferable to paint them black to prevent light leaking through. I did not paint them but they turned out to be ok because of sufficient thickness.

Step 7: Bokeh Effect Pictures

Now , put the lens cap that you built on your camera lens and choose one of the designs you made and place it in the slot of the lens cap.   
To test the lens,
1. You need some lights. I placed some christmas lights on a clothes drying rack and placed it a few feet away from the subject.
2. Keep the subject as close as possible and keep the subject in focus and make sure the lights are a blur.
3. Set the camera to the largest aperture.
4. Set the shooting mode to Av or Manual.
5. Fire away!!

You can experiment with different filter shapes, different distances of lights in the background, different types of point sources of light.  You can create interesting visual background effects with various shapes of filters.

There is vignetting effect seen on the pictures. This could be due to bigger size of the circular discs. It would be better to make the designs much smaller.  Also increasing the distance between the subject and the lights increases the quality of the blur.

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