Using a Polarising Filter to Depict the Sky in a Deeper Shade of Blue
Much as we would like the sky to be a clear, deep blue in our daytime outdoor photographs, Mother Nature doesn’t always cooperate. But your options aren’t limited to fixing it in post-processing or making do with a low-contrast, dully-coloured sky. In this article, we share how you can use a polarising filter to intensify the colours of the sky. (Reported by: Teppei Kohno)
EOS 750D/ EF-S10-22mm f/3.5-4.5 USM/ FL: 15mm (24mm equivalent)/ Aperture-priority AE (f/8, 1/320 sec)/ ISO 400/ WB: Auto
Taken without using the PL filter
Compared to the image at the top, you can see that the contrast is lower and the blue is a lighter shade.
What is a PL filter?
A polarising (PL) filter is a filter that you attach to your lens to reduce certain polarities of light (Here's a more technical explanation of how PL filters work from Cambridge in Colour). It removes unnecessary reflected light, and therefore not only controls glare and reflection, but also helps to make colours appear more vibrant. It can even reduce light haze, fog or mist. If you want to elevate your photography, it certainly is a good investment.
There are two types of PL filters: Linear and circular (Read about the difference here.) As linear PL filters might interfere with AF and through-the-lens light metering on cameras with mirrors (i.e. DSLR cameras), circular polarizing filters (CPL filters) are more commonly used and also more widely sold. Other than that, the visual effects of both are the same.
Step-by-step: How to use a PL filter
A: Attach the PL filter to the lens.
B: Shoot with the sun behind you.
C: Rotate the PL filter and check the result to see if you have obtained the desired effect.
A: Mount the PL filter onto the lens
Select a filter that matches the filter thread diameter of your lens. Attach it to the screw threads at the front of the lens. Turn the filter right to screw it firmly in place.
- If you own multiple lenses, you might want to choose a filter that matches the lens with the largest thread size, and then use step-up rings to adapt the filter to the lenses with the smaller thread sizes.
- If you are using the EOS RP or EOS R and have multiple EF lenses, you can also consider getting the EF-EOS R mount adapter with the drop-in CPL filter. It effectively adds a filter to all your lenses, regardless of their thread size.
B: Shoot with the sun behind you
The PL filter has little effect if you shoot in backlight. Make sure that you shoot in front light, i.e, with the sun illuminating your subjects from behind you.
Good example: The blue looks more intense when captured in direct light
EOS 750D/ EF-S10-22mm f/3.5-4.5 USM/ FL: 13mm (21mm equivalent)/ Aperture-priority AE (f/8, 1/60 sec, EV+1)/ ISO 200/ WB: Auto
To bring out the effect of the PL filter sufficiently, find a location that allows you to shoot in front light.
Negative example: No effect when shooting in backlight
EOS 750D/ EF-S10-22mm f/3.5-4.5 USM/ FL: 16mm (26mm equivalent)/ Aperture-priority AE (f/8, 1/200 sec, EV+0.7)/ ISO 200/ WB: Auto
The closer your camera is pointed toward the sun, the weaker the effect of the PL filter. With backlight such as this, the PL filter will have almost no effect.
Tip: The effect of the PL filter is strongest on the parts of the sky that are at a 90-degree angle from the sun. When the sun is high in the sky, the polarisation effect is strongest near the horizon. When it is low in the sky, the polarisation effect is strongest in the sky directly overhead. More examples of the effects of sun position here.
C: Rotate the PL filter and check the result to see if you have obtained the desired effect
A PL filter has 2 layers. Rotating the frame at the front can make the effect weaker/stronger. Adjust it until you find the angle that gives you the deepest shade of blue.
Tip: When adjusting your PL filter, try turning it right whenever possible. If you do have to turn it left, be careful not to unscrew the filter by accident!
The front frame of the PL filter can be rotated 360 degrees, with the effect changing roughly every 90 degrees. After confirming which angle is most effective, you can finely adjust the angle to obtain your desired effect.
Important note: Using a PL filter slows down shutter speed
The PL filter works by restricting incident light, which results in a slower shutter speed if you are shooting in Program AE or Aperture-priority AE mode. This might be great for some creative intents, but it also increases the chances of subject blur and camera shake. Take precautions to prevent: Use a tripod if necessary, or increase the ISO speed to make the shutter speed faster.
The images above were shot with this Canon filter:
Circular polarizing filter PL-C B
The filter is available in diameters of 52mm, 58mm, 67mm, 72mm, 77mm, and 82mm. You can also attach a lens cap on top of the filter.
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Born in Tokyo in 1976, Kohno graduated with a Social Work degree from the Department of Sociology of Meiji Gakuin University, and apprenticed with photographer Masato Terauchi. He contributed to the first issue of photography magazine PHaT PHOTO and became an independent photographer after that, in 2003. The author of many books, Kohno not only shoots all sorts of commercial photographs, but also writes prolifically for camera and other magazines.