Linear or Circular?
First thing you should know is that there are two varieties - linear and circular. Although they're both physically round, a linear variety can have an effect on the autofocus or metering accuracy of any camera that uses a semi-silvered mirror or prism to split the light entering the viewfinder. This is known as a beam splitter and is used by most modern SLRs to calculate exposure and focusing distance.
As a rule use a circular filter if you have an autofocus camera or a manual focus model with a spot meter such as the Canon T90 or any modern digital SLRs.
Screw-in or System filters?
Next thing to decide is whether to buy a round, screw mount filter or a system version that slots into a filter holder. Round ones are often easier to adjust and feel better built. They're also more compact to carry around. The disadvantage is larger sizes are more expensive and, if you have two lenses with different filter thread sizes, you may need to buy two filters, whereas a system type would just need another adaptor ring for the filter holder.
The filter holder type can also cause vignetting when used on some larger thread wide-angle lenses. Equally, a larger filter holder may prevent vignetting when used on a smaller thread wide-angle.
Features to look for
- If you have a camera without through-the-lens viewing look for a filter that has an index mark printed on it. This will help you align the filter correctly.
- Some filters have a small screw-in arm to help rotate the filter, which is useful if you intend using the filter when wearing gloves in cold weather.
- Filters with thick rims can cause slight vignetting when used on wide-angles. The latest Pro1 D versions from Hoya have slim rings.
- Check whether the filter is circular or linear. It will often say PL CIR if it's circular, while linear often just has polariser or PL marked on the rim.
- Polarising filters for square system holders are still round so they should rotate easily in the holder.
Screw-in filters
Screw in filters attach to your lens' filter thread and are the least bulky option. If you have a number of lenses with different filter threads it can be an expensive option.
B+W
A brass mount with solid ring and deep filter thread make this a heavy filter that feels substantial compared with its Japanese competition. Extremely neutral throughout the range with plane parallel polariser material that the German makers, Schneider, say will guarantee optimal image results. The one to choose if your budget can stretch to the hefty price tag in sizes from 46 to 95mm.
Hama
Suppliers of one of the largest accessory ranges made, with thousands of items for video, stills and audio markets. Recently they have introduced a range of silver finish filters that match the modern styles seen with newer compact digital cameras and AF SLRs, This range includes the HTMC Circular polariser in sizes from 25.5mm to 77mm. In conventional black rimmed options there's a Linear in sizes from 49mm to 82mm, Circular in sizes from 27mm to 82mm and a HTMC circular in sizes from 37mm to 86mm. Hama also produce an slim mounted circular version for wide-angle lenses in sizes from 49mm to 77mm.
Heliopan
Ksemannn polarising are very expensive, but different in that the after the sandwiching of the polarising layer the filters are polished plane parallel and the edges are thoroughly sealed and mounted in a precision rotating mount with numerical scale. The special seal helps if you're using it in difficult climates such as sub tropical. They are available in linear or circular versions along with a linear warm polariser all in sizes from 39mm to 105mm along with Hasselblad and Rollei bayonet mounts.
Heliopan linear and circular polarisers are made from top quality Schott glass (made by the Zeiss group) and come in black anodised brass mounts in sizes from 39mm to 105mm.
Hoya
Super HMC Pro Multi-coated circular polarisers are difficult to make because the heat needed to multi coat the outer surfaces can damage the polarising sheet that's sandwiched between the glass. Hoya have managed that with this version available in sizes from 49mm to 82mm and it's ultra thin and lightweight. Hoya also make a normal circular polariser in sizes from 27mm to 86mm and linear in sizes from 39mm 95mm.
Jessops
Produce a wide range of low cost screw-in filters including linear options in sizes from 46mm to 72mm and circular varieties in sizes from 27mm to 77mm.
Kood
Have a range of screw fitting polarisers in sizes from 39mm to 86mm for the linear variety and 27mm to 86mm for the circular versions. They also produce 84mm linear and circular versions for use in Cokin P series holders.
Sigma
The company that makes lenses also has a range of circular polarisers with slim mounts for their lenses. They range in sizes from 46mm to 82mm for normal coated versions and there's also a multi-coated version in sizes 86mm, 95mm and 105mm.
System filters
Square filters fit onto your lens with removable adaptor rings. You only need one holder and one filter which can be attached to a variety of lenses using different size adaptor rings.
Cokin
French manufacturer Cokin was the originator of the special effects system with A (amateur) and P (professional) sizes. The A series are 67mm square and designed for use on 35mm cameras while the 84mm square P series are more suitable for larger medium-format systems and also come in handy when you use wide-angles to helps prevent cut-off.
More recently a larger Z-Pro and X-pro range were added to accommodate those lenses with large filter threads, especially suitable for the modern ultra wide-angle lenses.
Both linear and circular polarisers are available, which are very neutral in colour. Unlike other resin Cokin filters these are mounted in glass making them much heavier. They fit into the filter holder's back slot so you can rotate them easily.
Cromatek
A British brand with a unique box shaped filter holder that holds the 76mm filter in place while acting as a lens hood. The filter fits into the back slot of the box holder and you have to flip down the cover of the box to rotate the filter. This can slow you down, but you do gain the benefits of a superb light tight hood. A 100mm version is also available and both are glass mounted with circular or linear options.
Hi-tech
An 85mm system with an option of attaching a 105mm screw thread Kaesemann polariser to the front of the 100mm holder.
Jessops
Jessops make a range of budget priced filters for their effects filter system which are, like Cokin, available in two sizes Standard (67mm slot) and Professional (83.5mm slot). Linear and circular polarisers are available in each system.
Lee
A system originally developed for the professional photographer who needs the very best quality. The filter holder is larger and accepts 100mm square filters. Their linear polariser is made from Butyrate and is less than 1mm thick so needs to be mounted in a gelatine holder for the best support. It's available in 75mm, 100mm and 150mm square versions.
Hoyarex
Square system from the popular maker Hoya. A wide range were made and the system had a useful rubber hood that attached to the outside of the filter holder. Several of the filters in this range were glass. The system was 75mm square and excellent quality. You can pick these up second-hand and they're well worth the investment.
Source: http://www.ephotozine.com
