Introduction: Bokeh Filter DIY
Bokeh (bo·keh \ˈbō-kā, -kə\ ) or the blurred quality/effect in the out of focus are of a photograph is not only fun to play with, but also easy to alter. Simply place a custom paper/carstock cutout (filter) in front of your lens and go shoot.
Step 1: Tools and Materials Needed
Assuming you have a camera with interchangeable lenses, you will need:
- Fast Prime Lens
- Compass, or Lens Cap
- Black cardboard
- Scalpel/ craft knife
- Cutting mat
Step 2: Determine Filter Size
Either measure the inner diameter of your lens or look on the inside of your lens cap for the the size and downsize 2-3 mm so the filter sits closer to the front element. You will have better results when your new filter is closer to your lens.
If you don’t like the metric system, I used 2.0 inches for 52 mm diameter lens & 3.0 inches for 72 mm
Step 3: Make a Filter Template
Using your compass, trace a circle sized for your lens and poke the compass through the paper in the center before removing it.This will make centering the cutout/design much easier. The tabs are optional and don’t need to be perfect, they just help in removing the filter.
If you don’t have a compass or you don’t want to measure, just trace your lens cap and cut on the inside of the line so the filter will fit closer to the lens.
Step 4: Determine Maximum Cutout Size
The table above has the maximum cutout sizes for a few lenses, you could also just try a size and see what happens or you could calculate the max size yourself:
We are making a new aperture for your lens, so we need to make the cutout smaller than the lens’ largest aperture. Since an f-stop is a ratio of focal length to the diameter of the aperture we simply divide the focal length of the lens by its widest aperture. For example a 50mm f/2 should have a cutout smaller than 50/2 or 25 mm (0.98 in)
Step 5: Trace Your New Filters
Use your new template to trace your filter blanks and add a little mark in the center of the circle (where you poked a hole with the compass). This will help you center your cutout.
Use your center mark and get creative drawing in different shapes. I like pencil for this, but for clarity I used a thick marker in the photos.
Step 6: Cut Out Filters
Now you are ready to cut out your shapes and filters. Start with the center design, this will give you more room to hold onto the card-stock while working with a knife. Then use scissors to cut out the circle and tabs.
Step 7: Camera Settings
Set your camera to Aperture Priority (A on Nikon, Av on Canon) and use your largest aperture (f/4 to f/1.2)
With smaller or complex designs:
- Place camera on a tripod.
- Prefocus on your subject.
- Set camera to manual focus.
- Place the filter in front of your lens.
- Take photos.
Step 8: Notes
Some light meters and metering modes will not be accurate with small designs, so check your exposures and bracket as necessary.
Variables to play with:
- Camera-subject-background distances
- Angle of light source if using a reflective background (see photo of R2D2)
- Cutout size
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