In the past a neutral density filter has been an essential tool for landscape photographers looking to control strong light to get a more balanced exposure, however now that there are good software filters available in photo-editing tools, the need for one is often questioned and debated within the photography community. Here are the pros and cons of both, and some other solutions photographers use:
Hardware ND (neutral density) filters
Hardware ND filters such as the Lee Filters 0.9 ND have been around for years and stood the test of time. Why? because they are an integral tool to landscape photographers.
The cost of a hardware neutral density filter can vary quite a bit between brands, but the quality can vary too, especially with the build quality ad colour casting. Once a photographer has used one though they will never want to leave home without one! However, buying multiple filters with different strengths and levels of gradient can soon mount up in price.
Hardware filters are great for shooting landscapes and seascapes, making balanced exposures much more controllable and easier to get right in camera. For seascapes, a hard edge is better rather than a soft gradient so you can place the exposure line on the horizon.
Software ND (neutral density) filters
Software filters such as those in Adobe Camera Raw and Adobe Photoshop Lightroom have changed the game for many photographers. The ability to add a gradated overlay to a photo and make local adjustments is powerful, especially on raw images. There is a huge amount of control available including more flexibility on where the gradient begins and ends and how intense it is. This variation is not as flexible in hardware equivalents unless you have a collection of different strength filters.
Another benefit to software filters is the lack of needing to carry around additional filters or having to mess around fitting them to the end of your lenses; especially if you are changing what you are shooting and lenses a lot.
Manually merging a correctly exposed sky
Merging a correctly exposed sky is one of the oldest ways of solving harsh skies in photos for digital photographers. Processing can become really time consuming though, especially if you are editing multiple complex photos. The results can be great, but this is a solution that is only viable for a few photos at a time unless you have plenty of time to edit your photos.
In recent years there is another option that a lot of people use to combat strong lighting issues, and that is to use HDR (high dynamic range). This technique is a bit like Marmite for many photographers; mainly due to it being so overused in the community, with many photographers being a bit too slider happy. For static scenes multiple exposures can work well, however in scenes with lots of movement the multiple exposures will have blurring, so will not be as effective. When done well HDR can be highly effective.
So, which is best?
For me there is no substitute for the real thing; especially when I have the time to properly set up and compose landscape shots, however software ND filters really have their place. I use software ND filters a lot and they make a great solution for creating great images in difficult lighting.
One issue with software and hardware filters is that if the main subject of the photo crosses the horizon it is also graduated by filters. This is where software filters now have an edge! Since adobe released Lightroom CC (or Lightroom 6 if sole separately) you now have the option to easily brush out the filter over subjects to negate this effect which is brilliant.
So, which do I use? I use both, often on the same photo especially in dynamic lighting situations. I feel it gives me much more control over my editing. If I am wandering around shooting hand-held though and do not want to be bothered with lugging a filter holder around on the end of my lens, I will happily fall back to a software solution. Which do you prefer?