Camera filters are as important and useful as ever. There are still things you can't do in Photoshop or with Instagram filters.
Photo editingsoftware can only manipulate the captured image, but physical filters can modify what the sensor actually sees. So let's move on to the real question here.
What do you really need? Well, like most questions in photography, it really depends on what you're doing. Landscape photographers tend to need filters much more than portrait photographers (although a 1- or 2-step ND can be very useful for a portrait photographer shooting outdoors). So yes, professional photographers use filters when taking and editing photos. Each type of filter or editing preset is used as a tool to enhance an image and offer more creative options.
Even for the most novice photographers, using filters can offer many advantages. Camera lens filters can serve different purposes in digital photography. They can be indispensable for capturing landscapes in extremely difficult lighting conditions, they can improve colors and reduce reflections, or they can simply protect the lenses. Filters are widely used in photography and cinematography, and while some only use filters in rare situations, others rely on filters for their daily work.
Filters alter the light entering the camera or keep the front of the camera lens protected, making them useful accessories no matter what you shoot. All photographers should consider adding a UV filter to the front of each lens to keep them protected from scratches. Graduated Neutral Density filters can have a big impact by preventing the sky from being overexposed, while a polarizing filter has a handful of uses that most photographers can easily participate with. Filters are relatively inexpensive, but they can make a dramatic difference in many types of photographs.
When shooting landscapes, I often use a polarizing filter to bring colors to life, darken the sky and reduce haze. This is usually measured by the number of stops (in shutter speed, aperture, or ISO) that you would have to adjust the camera settings to have adequate exposure compared to without the filter. A 3-pass ND filter allows you to increase the shutter speed or widen the aperture in three light steps, while a 10-point ND filter is much stronger and gives you ten steps to work with. Many people with anti-filter also wonder if a filter will actually protect their lens in most situations.
Keep in mind that each of these filters has a very different effect, and whether they work for you will depend to a large extent on the type of subjects you record and your shooting style. The main drawbacks are that obviously there is always some polarization (and not in a direction that you control other than partially unscrewing the filter), so if you want a completely depolarized capture that becomes impossible, and that at high densities there tends to be a lot of “corner darkness”. at least in my copy (I'm not sure if it's just a quality problem with my copy). And the soft GND filters are ideal for capturing scenes with more complex horizons, such as a sunrise over a mountain range or a sunset over a field full of trees.
Personally, I prefer to keep a transparent filter on my lenses at all times, because they are easier to clean. Because the size of the sky compared to the foreground can change depending on the composition, most GND filters are manufactured in a rectangular shape. As a professional photographer, your job is to capture the best possible image; both the lens and the editing filters help to achieve this. As for photo editing filters, changes in exposure, color, contrast, and more help improve an image in ways that aren't possible on the camera.
For example, you can eliminate reflection in a lake or see clearly through a window with one of these filters. This will help in any type of photography and can even act as a 1-pass ND filter, as it blocks almost that amount of light, making it useful and versatile. .