Complete Guide to Camera Filters for Digital Photography: Techniques and Tips

Explore the world of filters in digital photography with this comprehensive guide on discovering, selecting, and effectively using different types of camera filters.

Author: Marco Crupi

This article is a segment of the Digital Photography Course. Click here to return to the main course overview.

In digital photography, many effects that were once only possible in-camera can now be achieved in post-production. Despite this, physical filters remain a staple in a photographer’s toolkit because some effects simply can’t be replicated in Photoshop.

Colored filters were once popular in black-and-white film photography, particularly among landscape photographers who used them to lighten or darken specific areas of an image. Nowadays, their effects can be entirely recreated with editing software.

In Photoshop, you can explore the impact of these filters by navigating to “Image -> Adjustments -> Black & White,” which allows you to simulate how colored filters would affect your photos.

Unlike colored filters, a polarizing filter is a must-have because its effects are impossible to replicate with any software.

Polarizing filters work by managing reflected light from surfaces like water, glass, and atmospheric particles, eliminating unwanted reflections from non-metallic surfaces and enhancing contrast. You can also use the filter to either reduce or emphasize reflections by rotating it, allowing you to achieve the desired effect. For example, when photographing water, rotating the polarizer can either minimize reflections to reveal the details beneath the surface or enhance them for a dramatic effect.

Polarizing filters are also useful when shooting through glass, as they help eliminate reflections, making them ideal for photographing artwork or storefronts without capturing your reflection.

Types of Polarizing Filters:

• Linear Polarizers – These can cause issues with autofocus and exposure metering systems on modern cameras that have sensors positioned behind partially reflective elements, such as mirrors.
• Circular Polarizers – Recommended for modern DSLRs and mirrorless cameras, circular polarizers work without interfering with autofocus or metering. They mount directly onto the lens, and you can observe the changes in the viewfinder as you rotate the filter.

Keep in mind that polarizing filters are most effective when shooting at a 45° to 90° angle to the sun. They typically absorb about 2 stops of light, so adjustments to exposure settings may be necessary. The filter also enhances color saturation naturally, reducing the need for extensive color correction in post-production, which is particularly beneficial in landscape photography, as it deepens blue skies and enhances color separation.

Effect on Black and White Photography: Polarizing filters are particularly valuable in black-and-white landscape photography due to their ability to create a distinct tonal separation. For example, in two identical black-and-white images taken with and without a polarizer, the one with the filter will display a broader range of tonalities. By lowering the blue channel in Lightroom’s HSL panel, only specific areas like the sky will darken, leaving elements such as clouds unaffected, unlike in a shot without the polarizer, where the entire image might darken uniformly.

I want to emphasize that the exposure in the original shots was perfectly correct: ISO 100 – F/13 – 1/40 sec for the one with the polarizer and ISO 100 – F/13 – 1/160 sec for the one without the polarizer (the ambient light was that of early afternoon on a summer day in Sicily).

With a narrower tonal range to work with in the photo without the polarizer, it’s challenging to create a clear difference in terms of brightness and black-and-white shades between different parts of the image. Lowering the “Blue” to -100 in Lightroom’s HSL panel darkens the entire photo.

In the photo where I used the polarizer, I had a much wider range of tonalities to work with. Lowering the “Blue” value only darkened certain parts of the image, specifically the sky (excluding the clouds, which remained white to light gray) and some sections of the sea.

I was even able to create a greater separation between the various shades of the sea—something impossible in the photo without the polarizer, where I couldn’t even separate it from the sky.

Another type of filter that cannot be replicated in Photoshop is the ND filter (Neutral Density). ND filters reduce the amount of light entering the lens without altering the color balance. They come in various strengths, such as ND2, ND4, and ND8, indicating the number of stops by which they reduce light.

The ND2 cuts light by one stop, ND4 by two stops, and ND8 by three stops, continuing progressively darker. These filters are essential when you want to use slower shutter speeds in bright conditions, such as capturing motion blur in waterfalls or smoothing out ocean waves during daylight hours.

Example: The images shown were taken using an ND1000 filter, which is so dark that it’s almost impossible to see through it, allowing for extremely long exposures even in broad daylight.

Graduated Neutral Density (GND) filters are among the types of filters that simply can’t be replicated digitally. As the name suggests, GND filters gradually transition from dark to light, typically darker at the top and transparent at the bottom. This gradient helps balance exposure changes within a scene. For instance, when shooting a landscape, they allow you to darken the sky more than the ground below the horizon, helping to achieve a balanced exposure.

It’s generally better to use square or rectangular slide-in filters (though screw-on versions exist) because they let you adjust the height to match the gradient with the horizon line. These filters are extremely useful for balancing the brightness levels between an overly bright sky and a darker foreground. Have you ever taken a landscape photo, urban or natural, where the trees or buildings are correctly exposed, but the sky is blown out? Using a GND filter can solve that problem. Be careful, though, to keep the dark area of the filter above the horizon line; otherwise, the effect might look unnatural.

As you can see in the second photo, the use of a GND filter allows me to maintain correct exposure on both the sea and the beach, preventing the sky from being overexposed. This gives me more flexibility in post-processing; editing a well-exposed sky is far easier than working with blown-out highlights.

In the first photo, without the GND filter, the camera had to find a compromise between the different parts of the image, and the difference between the two photos is quite obvious.

GND filters come in two main types: soft and hard. Hard GNDs are ideal for scenes with well-defined horizons, like the sea, while soft GNDs have a gentler transition, making them perfect for mountain landscapes or scenes with trees where the horizon is less defined.

For sunsets over the sea with the sun directly in front, reverse graduated filters are recommended. These are essentially soft filters in reverse-they have a hard transition in the middle of the filter that gradually softens toward the top, making them perfect for such challenging lighting conditions.

One filter that doesn’t affect the image but is still incredibly useful is the protective filter, which, as the name suggests, is designed to protect your lens from impacts and scratches.

If you choose to use one (even though a lens hood already provides some protection for the front element), I recommend not skimping on quality. A cheap protective filter can negatively affect your image quality, so investing in a good one is worth it.

After exploring the various types of filters, there’s a practical consideration: most photographers use more than one lens, and these lenses rarely have the same diameter. This would mean buying a separate filter for each lens, which can quickly become expensive. Luckily, step-up and step-down rings allow you to use the same filter across multiple lenses with different diameters, saving you both money and hassle.