When you're ready to use filters for noticeable photographic effects, CPL (Circular Polarizing) filters are the perfect starting point for beginners. They are easy to use and deliver striking results.
I. What is a CPL Filter?
CPL is the abbreviation of Circular Polarizing Filter.
It is one of the most commonly used optical filters for photography and videography. Mounted on the front of the lens, it filters out stray polarized light, eliminates reflections, and enhances color saturation and contrast. It is widely used in landscape, portrait, street, aerial and mobile photography.
II. Core Functions of CPL Filters
1.Eliminate reflections on non-metallic surfaces
l Glare and harsh reflections on glass windows, car windows, water surfaces, tiles, plastics, painted surfaces and leaves.
l When shooting glass displays, taking photos through car windows, or capturing lake surfaces, it removes washed-out white reflections to reveal details underneath.
Note: CPL filters cannot eliminate metallic reflections; they only work on non-metallic diffuse reflection and polarized light.
1. Darken the sky and enhance blue sky with white clouds
On sunny days, it deepens the blue of the sky and adds layered texture to clouds.
It prevents the sky from appearing pale white and is a must-have for landscape photography.
2. Improve color saturation and image clarity
It makes greener plants, clearer water and richer architectural colors.
It reduces atmospheric haze and scattered stray light for a cleaner, more transparent image.
3. Reduce water surface glare to see through the water
When shooting rivers, ponds and the sea, it weakens sparkling surface reflections, allowing you to vaguely see underwater stones and aquatic plants.
4. Slight light reduction
Most standard CPL filters provide about 1~2 stops of light reduction. Under strong sunlight, it slightly lowers the shutter speed and helps achieve background blurring with a large aperture.
III. Working Principle of CPL Filters
1. Characteristics of Natural Light
Sunlight is unpolarized light, with light vibrating in all directions.
When light hits water surfaces, glass, the ground or atmospheric dust, it turns into unidirectionally vibrating polarized light, which appears to us as harsh glare and a hazy white mist effect.
2. Structure of Polarizing Filter
A CPL filter consists of two layers:
Linear polarizing layer: Only allows light in a single direction to pass through, filtering out stray polarized light from other directions.
1/4 wave plate: Converts linearly polarized light into circularly polarized light, compatible with the autofocus and metering of DSLR and mirrorless cameras.
(Linear PL filters interfere with camera metering and focusing, so CPL is widely used nowadays.)
3. Adjustment Mechanism
Rotating the outer ring of the filter changes the light transmission angle of polarization.
When rotated to a certain angle: it perfectly blocks glare and stray light in the sky for the strongest effect.
Further rotation will gradually weaken the effect until it disappears completely.
4. Key Angle Rule
The CPL filter delivers the best effect when the sun is at a 90° side angle to the lens.
It barely has any effect when facing directly toward or away from the sun.
IV. How to Use a CPL Filter
1. Installation
Choose the size matching the lens caliber (such as 49/52/58/67/77/82mm), then screw it onto the front of the lens.
2. Operating Steps
Install the CPL filter and frame the shot normally.
Look through the viewfinder or screen, and slowly rotate the outer ring of the filter.
Observe the image changes: the sky turns bluer, reflections disappear, and colors become richer. Stop adjusting when you get a satisfying effect.
Then perform normal focusing, metering and shooting.
3. Practical Usage Tips for Scenarios
(1) Shooting landscapes and blue skies
Stand sideways to the sun, rotate the filter slowly to darken the sky to a deep blue while retaining cloud layers.
Avoid over-rotation, otherwise the sky will turn unnaturally pitch black.
(2) Shooting through glass and shop windows
Get close to the glass and rotate the CPL until surface white glare is completely removed, so you can capture the scenery inside clearly.
(3) Shooting water surfaces and lakes
Rotate the filter to reduce bright glints on the water, making the lake look cleaner with richer layers.
(4) Shooting green plants and leaves
Eliminate whitish reflections on leaf surfaces, making the color of leaves more vivid without a dull gray tone.
The above content introduces CPL filters from multiple perspectives. Hopefully it can provide you with more references for selection and usage.
Share:
Is the DJI Pocket 4 Worth Buying?
What does an ND（Neutral Density） filter do? ND filter guide for beginners.