An Essential Part of Gear
The Circular Polarizing filter is essential gear for any landscape photographer but never more essential than a good tripod.
CPL filters are mainly to cut down the suns brightness to give sky a darker shade of blue and saturated colors throughout an image. It is also to cut down reflection in watery locales thereby showing elements under the water’s surface be it rocks, pebble, little fishes or hairy toes. The rotating front element of the CPL gives this filter a shaded gradient so for best results use with lenses that do not have a rotating front element.
CPL filters do not affect the overall color balance of a photo. A good quality filter can remain on the lens throughout a photo walk during daytime. And good quality means steep price. Common traits in a good CPL filter: light weight, cost a few thousand Philippine pesos at the least and be multi-coated (have greenish/violet sheen on the surface of the glass when inspected at a perpendicular angle to the eye). The price of filters also accounts for the manufacture of good threads for screwing on and off the lens easily. El cheapo filters will sometimes get stuck too tightly on the front element of the lens (definitely not good) and having to take it off sometimes mean a trip to the service center. CPL filters come in standard diameters of 52 mm, 55 mm, 58 mm, 62 mm, 67 mm, 72 mm, 77 mm, 82 mm and 87mm.
Lenses with any focal lengths can use CPLs but there are arguments against using them on ultra wide-angle lenses (Canon EF-S 10-22 f/3.5-4.5 IS USM, Tokina AT-X 116 11-16mm f/2.8 PRO DX, Sigma’s 10-20 f/4-5.6 EX DC HSM and 8-16 f/4.5-5.6 DC HSM, etc.) due to the varying polarization of the sky from one end to the other-meaning, if CPL filters are on UWA’s one part of the sky will be much darker than another part. But with enough practice this phenomena will lessen.
The CPL filter in question here is the Kenko PRO1 Digital S CPL Low Profile Frame(LPF)/Digital Multi Coated(DMC) at 67mm mounted on a Canon EF-S 17-85mm f/4-5.6 IS USM lens. It is a joy to use and very easy to handle. This particular filter has been on many trips and has saved a few photos from being over exposed.
There is an arrow or dot on the front of the CPL filter. It is a guide to indicate the darkest part of the glass. A rule of thumb is to turn the arrow 90˚ to the sun. But turning the rotating part to achieve a result you want is the best way to go and meter the scene as you do so (half press on shutter button to check exposure). The CPL filter will cause the DSLR meter to under expose by a stop to stop and a half (-1 to -1 1/2). To correct this just adjust aperture and open up 1 stop (ex: at f/8 just correct to f/7.1 or adjust exposure compensation) or do a longer exposure during day time. If shooting RAW format correct during post processing. This is just a basic guide. Always experiment with the rotating front element of the CPL filter to achieve your best results.
Affordability and the quality that go with a certain price is the usual argument and there are many schools of thought on CPL filters. Yes, there are also many branded CPL filters in the market. The Kenko is moderately priced and of good Japanese quality. The German-made B+W CPL filter is the best and at 77mm cost PHP8700.00 (approx. US$200) while a Kenko CPL of the same size is a third of that amount. Kenko, Hoya, and Tokina brands are all under one roof at THK Photo Products Inc.. THK is one of the biggest manufacturer and suppliers of glass to a number of camera companies. It would not be surprising if they supply to Canon, Nikon, etc. It is definitely better to buy a filter that comes from a company with a long history rather than getting one from an unknown brand.
Sometimes we just can not choose what time of the day to shoot in. Going with any given situation is usually the norm and it is better to have a Circular Polarizing filter in the gear bag.