A star filter lets you create beautiful starbursts even when using a large aperture (small f-number). Here’s how to create your own to play with, using materials from a stationery store! (Reported by Kazuo Nakahara, Digital Camera Magazine)

EOS R7/ RF50mm f/1.8 STM/ 50mm (80mm equivalent)/ Aperture-priority AE (f/2.8, 1/30 sec, EV -0.7)/ ISO: 400/ WB: Auto

This homemade star filter has grooves that create lovely long-rayed starbursts from each fairy light.

 

Create beautiful starbursts even with a wide aperture!

You might be familiar with using a narrow aperture such as f/11 or f/16 to create starbursts from point light sources. (See: Guide to Creating a Starburst Effect with the Sun and Lens FAQ: What Are Aperture Blades? How Do They Influence My Photos?) A star filter lets you do the same, but with a much wider aperture: as wide as f/4 or even f/2.8. You can even change the orientation of the stars by rotating the filter.

No filter, f/2.8

 

How to make a star filter

Preparation: Things you need

The star filter I used in the main image was created using items you can find in a stationery shop, or might even already have at home. I bought items 1-4, shown below.

1. Clear plastic card (A4 size)
This will become your filter. I recommend rigid plastic such as a hard card case or transparent table mat.

2. Graph/square-lined paper
This will help you draw grooves on the filter. The grids should ideally be 5mm or smaller—if they are too big, the stars won’t look good. You can also find a template online and print it out.

3. Cutter/hobby knife
For cutting grooves onto the plastic sheet. The picture shows a hobby knife I found in the stationery shop—it is easy to handle, like a pen, and makes the job easier. If you can’t find this, a normal box cutter/penknife works, too.

4. Compass
For drawing circles.

In addition, you will also need these 2 items, which you most likely already have at home:

5. Ruler

6. Sticky tape

Step 1: Draw your design on the graph paper

i) Using the compass (A), draw a circle with a diameter 10mm bigger than your lens filter thread onto the graph paper (B). For example, if you want to create a filter for the RF50mm f/1.8 STM, which has a 43mm filter, your circle should be at least 53mm.

Tips:
- Make the circle big enough to fit your biggest lens.
- Use the graph paper squares to help you measure. The grid pattern will come in useful later on.

ii) On the same graph paper, draw a rectangle around the circle. I added an extra tab to the design to make the filter easier to hold.

Step 2: Trace your design onto the plastic and cut it out

A: Graph paper
B: Plastic card

i) Place the plastic sheet over the graph paper and use a marker to trace over the filter design.

ii) Use the cutter or craft knife to cut out the filter design. Be careful not to cut yourself! This cutout will become your star filter. Now, we just need to cut grooves onto it.

Step 3: Cut grooves onto the filter

C: Plastic cutout
D: Circle you drew in Step 1
E: Sticky tape
F (shown below): Cutter or craft knife

i) Place the star filter plastic cutout on the graph paper over the circle you previously drew. Use sticky tape to stick the cutout to the graph paper so it doesn’t move.

ii) Then, using the grids of the graph paper as a guide, use the cutter or craft knife (F) to gently cut horizontal and vertical lines onto the graph paper so that they form a criss-cross pattern. Use a ruler to keep the lines straight.

The finished product, still taped onto the graph paper.

Pro tip: Uniformly spaced lines produce nicer stars

Tracing over the grids of the graph paper helps ensure all the lines are the same distance from each other. This is important if you want the points of the star to be the same length!

Step 4:  Use your filter!

Put your newly made DIY star filter in front of your lens to create lovely 4-pointed starbursts from fairly lights and other point light sources.

Tip: Underexposing the shot slightly makes the starbursts stand out better—you can do that when using an auto-exposure mode such as Av mode by using negative exposure compensation.

Bonus: Create 6-pointed starbursts

The number of points in the stars is determined by the number of directions of the grooves. To get nice 6-pointed stars, create grooves that form equilateral triangles, shown in the image above, instead of the “+” shape for 4-point stars. The diagonal lines are at a 60-degree angle.

EOS R7/ RF50mm f/1.8 STM/ 50mm (80mm equivalent)/ Aperture-priority AE (f/2.8, 1/30 sec, EV -0.7)/ ISO: 400/ WB: Auto

The stars in this image have 6 points.

 

Know this: f/2.8 to f/4 is the ideal aperture

Close-up crops

In the image shot without a star filter, there are starbursts at f/2.8, but very faint. Using a star filter crates starbursts with long rays. At f/11, some of the starburst rays are very short. Shoot at f/2.8 to f/4 for the best results.

More DIY projects for the crafty photographer in:
How To Create an Inexpensive Light Box From Scratch
3 Product Photography Essentials You Can DIY
How to Create a Sparkly Background with Bokeh Circles for Pretty Trinket Pictures
Homemade Light Diffusers: Different Materials, Different Output