Filters for Landscape Photography: Graduated Neutral Density Filters (GND)
Graduated neutral density filters (GND) are gradually darkened rectangular filters, where one end of the filter is black and gradually becomes transparent towards the other end. These filters are very useful in landscape photography as they help you balance the light disparities you might encounter in the field. As I mentioned at the end of my article about the histogram, there will be times (very often) where the sky is much brighter than the foreground and the dynamic range of the scene is so high that your camera sensor won’t handle it in one single exposure. You will either clip the highlights or clip the shadows. This happens with every camera, even the 5 billion dollars one. There’s no escape. Don’t despair yet, because here comes the GND to the RESCUE!!!!!
Due to the darkened side of this filter, you can “selectively” darken the sky (or the brighter part of your frame) to fix the light disparity; thus capturing a more balanced scene. You can see in this example below how the use of a GND helped me balance the light of my picture, recovering a lot of details in the sky. The RAW file on the left is taken without a GND and from the histogram, we can see how the light is everything but balanced. The steep peak on the right is formed by the bright pixels of the sky while the peak on the left represents the dark pixels of the building and the trees in the foreground. In this situation, the histogram tells us that this is a quite contrasty scene with dark shadows, bright highlights and very few mid-tones; hence, we do have a fair amount of light disparity. Sliding a GND in front of the camera evens the light coming from the sky, thus recovering a lot of details and balancing the frame. You can see from the RAW file on the right that the histogram has changed and that the steep peak on the right has broaden and has shifted towards the centre of the graph, meaning an even amount of shadows, mid-tones and highlights in the scene. In this case, using a GND helped me get a very balanced shot right in camera in one single exposure.
The incredibly geeky universe of GNDs
GNDs come in mainly 3 different types and 3 different strengths. The first and most common type is the Hard GND. This filter is called Hard as it has a very defined transition between the gradually darkened top part and the transparent bottom part, which usually sits in the middle of the filter. When you slide this kind of Hard GND in front of your lens, you’ll be able to see the filter transition line coming down your frame with a well-defined darkening effect. To achieve the best result with this filter, you’ll have to precisely adjust the darkening effect for a natural look. This will come easy if you have a flat horizon as you just align the filter dark edge with the horizon. This filter is very useful for seascape scenes as they usually involve a flat horizon like the image below. But what happens if you use this type of filter in mountain scenes? Well, you end up darkening the mountain too and this can negatively affect the lighting and look of your pictures. Don’t cry yet if you love mountain photography as much as I do…there’s a solution for us mountain people. Hoorayyyyy!!!
The solution is called Soft GND. This kind of filter fades from darkened part to transparent part in a rather gentle way. Whenever you slide a Soft GND in front of your lens, you’ll hardly see any clear sign of the darkening effect through your viewfinder or LCD screen. You’ll definitely see a shift in your histogram and you’ll then be able to recover more details in post-processing later on. You definitely won’t see the transition line coming down the frame with this GND. This filter has a more natural effect on your image and you don’t have to be super careful when positioning it in front of your lens. I mean, don’t be reckless with it, but surely you don’t have to be super precise as with the Hard GND. Due to this very subtle transition between dark and transparent part, this filter works very well whenever you have subjects protruding from your horizon; for example, mountains, tall cliffs and skyscrapers. Therefore, I really recommend it for mountain and cityscape photography. Here below you can see a comparison of the darkening effect of a Hard and Soft GND in a mountain scene. The Soft GND (RAW file on the right) clearly helped me to even the light in this scene without “blackening” the mountain and adding a very gradual and natural darkening effect to the picture, while the Hard GND (RAW file on the left) just darkened the mountain a bit too much for my taste. You also have to consider that I had to spend some time to adjust the transition line of the Hard GND for a natural darkening effect, while I had no issues when sliding the Soft GND. I know that the difference between using a Hard GND instead of a Soft GND seems very subtle, but trust me, you'll see this difference in post-processing.
Another less common GND is the Reverse GND. This filter has different effect as its darkest part is in the middle of the filter and it gradually fades towards the top. In this case, we have a very strong transition line as the transparent part of the filter is next to the darkest part. This filter is also perfect for seascape photography as its strong darkening effect will be on the horizon and it’ll help you to balance the light coming from the setting/rising sun. Honestly, I have never tried this kind of filter before and I have only included it because it seems a good choice if you are shooting seascapes a lot. Therefore, I don't have much to say about this filter. Recently, filter companies have also introduced a Medium GND type, which is basically a Soft GND with an even gentler transition area (so they claim). I had the opportunity to try one myself for couple of hours and I saw barely any difference from a Soft GND. Also, I wasn’t shooting mountains that day and I couldn’t really compare my Soft GND with the Medium GND. The first impression of the Medium GND wasn’t that good and it seems more like a commercial strategy to me, but, as always, I could be totally wrong.
Now that we have covered the differences between Soft, Hard and Reverse GNDs is time to talk about the 3 types of strengths of these filters. GNDs are usually classified by type and strength and, if you have been searching for GND filters, you might have stumbled across names like “GND Soft 0.9” or “GND Hard 1.2” or “GND Soft 0.6” and blah blah blah. The numbers you see refer to the strength of the darkening effect of the filter, which is 100% darkening effect on the top of the filter that gradually decreases to 0% into the transparent part. The most common strengths for GNDs are 2, 3 and 4 stops that respectively translates to GND 0.6, 0.9 and 1.2. Too many numbers, right?! I know my head hurts too. Basically, a GND Soft 0.6 is a GND Soft 2 stops, a GND Soft 0.9 is a GND Soft 3 stops and a GND Soft 1.2 is a GND Soft 4 stops. This means that a GND Soft 0.6 subtracts 2 full stops at the top of the filter as maximum darkening effect which then gently fades into the transparent part, a GND Soft 0.9 subtracts 3 full stops at the top and a GND Soft 1.2 subtracts a whopping 4 full stops at the top of the blackened part to then fade into the transparent part of the filter. Why so many different numbers you ask?! I guess photography companies like to confuse us, so we can buy more stuff from them. So, yeah market strategies! For this reason, I have included another high-tech stolen graph from NASA below that will help you un-confuse your head on GNDs once and for all.
What kind of GND should you buy first?
What kind of GND should you buy first? This is a legit question after you have explored and enjoyed the geeky world of GNDs in the previous paragraph. And the answer is…it depends, but I definitely have some recommendations for you. The first thing you should consider before buying a GND is what kind of landscapes you normally shoot. For example, I love mountains and I am lucky enough to live close to the Western Alps; hence, I am shooting a hell of a lot of mountain scenes. It’s what really drew me into landscape photography in the first place, so I have a love affair with mountainscapes. Therefore, I bought a Soft GND as it has a smooth transition that avoids blackening the mountains or any other protruding object from the horizon. So, if you love mountains and you shoot them a lot, the Soft GND is the right filter for you. If I were to focus my photography entirely on seascapes instead, I would probably consider a Hard GND to maximise the darkening effect of the sky on the flat horizon. In my personal and humble opinion, Hard GNDs are just a wee bit limiting compared to Soft GNDs, as you can definitely use Soft GNDs for seascapes too, but you can't really use Hard GNDs for mountain scene because of that harsh transition line. What if you like to shoot both mountains and seascapes? Well, as far as I know you have two options here. You either shoot seascapes with a Soft GND (which I do all the time when I shoot seascapes) or you suck up and buy both a Soft and a Hard GND. Simple as that. Which strength should you buy? This is a very personal choice as it is based on your taste and post-processing style. I always recommend the GND 0.9 as the darkening effect isn’t too weak or too strong. I have had a Soft 0.6 for a while and its darkening effect always felt very weak; often times so weak that I had to bracket the frame just in case. I have also tried a Soft 1.2, but I didn’t like that strong effect that it was casting on the scene which looked unnatural to me. So, I found my “go-to” GND filter in the Soft 0.9. I have had this type of GND for a while now and I have never been disappointed.
When NOT to use GND filters
This last paragraph might be counter-intuitive after all those praising words about GNDs, but sadly there are times where GNDs (even Soft GNDs) are not your best options. It happens sporadically, but it does happen. You can see from this straight out of the camera RAW file that my Soft GND has darkened the mountain top a bit and affected negatively my shot. Now, this might happen for 2 reasons:
a) My GND wasn’t positioned in a proper way for the shot.
b) Too much contrast between the mountain and the sky.
In this case, my GND was carefully positioned for the shot as I took extra care when I put it in front of my lens (I think), but that weird darkening effect happened because the mountain was quite tall and because the sun was rising right behind those peaks, creating a high contrast situation. I was half asleep as always that morning and I did not notice that the Soft GND had definitely a negative impact on my photo. In this case, you are better off without GND to achieve a natural look. Whenever you see that also the Soft GND is “blackening” your mountain, get rid of it. As said earlier, it happens rarely with Soft GNDs, but it happens and you need to be careful if you don’t want to spend endless hours in Photoshop to correct that mess. You are probably asking yourself: “What should I do in these situations?” The answer is Exposure Bracketing and then Exposure Blending in Photoshop. Don’t worry, I’ll go through these topics soon.
Another situation where GNDs are definitely not recommended is when you are shooting right into the sun. I am sure I have talked about this before, but for the so-called sunstar shots you don’t need any filters at all in order to avoid further annoying lens flares. So, no GNDs as well when shooting directly into the sun.
To conclude, GNDs are very useful gradually darkened filters to even out light disparities in your frame and generally to darken your sky in landscape shots. If you are a mountain junkie, the best GND you can get to step up your photography game is a Soft GND. The smooth transition from darkened and transparent area makes it the perfect fit for your mountain shots. If you are more like a seascape guy, you might want to consider a Hard GND, which is perfect for those flat horizon shot from the coast. You might have heard or read some photographers say that it’s useless to use GNDs nowadays due to the incredible dynamic range of the newest camera sensors or that the GNDs effect can be replicated in either Lightroom or Photoshop. This is partially true, but, in my humble opinion, GNDs help you to even the light in the scene, to reduce the work-load in post-processing, to easily visualise your shot on the field and more importantly to get the shot right in camera. This means that you can spend more time thinking about your composition and exploring new perspectives and worrying about bracketing or else.