Square filters versus circular filters
Most filters are round and screw directly onto your lens. However, square filters that are held in front of your lens by a metal frame can be a great option, especially for graduated filters that are half dark and half light. Square filters provide the option to slide the filter up and down to adjust how the gradient aligns with the horizon of your scene.
Variable neutral density filters
A variable ND filter is a filter that can be adjusted to block out different stops of light. This lets you go from two to eight stops of darkening without the purchase of several different filters.
Circular and linear polarizers
Polarizing filters are a unique type of filter that polarizes light and therefore removes or lessens the appearance of glare and reflections. These can help enhance the color and detail in photos of glass, water, the sky, buildings, plants, and more. The two main types of polarizing filters are circular and linear, and each polarizes the light in different ways. You can also purchase filters that do the jobs of both a polarizer and an ND filter at once.
“One of the things that I didn’t know early on is that ND filters are sized specifically to the diameter of the lens itself,” says Sidla. “And the problem with that is that the landscape photographer could have three, four, or five lenses, and they don’t typically have the same diameters.” Step-up rings are essential tools for this reason. These are screw-on adapters that can help fit larger filters onto your smaller lenses.
High-quality ND filters are an investment, so it’s best to buy one that is sized to your largest camera lens, and then purchase step-up rings so you can use that same filter for your smaller lenses as well.
Another way to avoid the purchase of multiple filter sizes is to try a clip-in filter. “It’s a filter that doesn’t go on top of the lens, but actually goes in front of the camera’s sensor,” explains Hernandez. “It’s game changing. You buy this filter, put it in front of the sensor, and you can use any lens you want.”