Long exposures with filters are a fascinating way to create stunning photos directly in the camera. I have been fascinated by this technique for many years and it comes as no surprise to me that numerous subscribers to my YouTube channel ask me for filter recommendations. Given the increasing frequency of these requests, I decided to write an in-depth blog post on the subject.
Photography with ND (gray filters) can be expensive, but it's important not to go for cheap alternatives that could cause frustration later on. The adage “buy cheap, buy twice” definitely applies here. A high quality filter set is crucial to avoid frustration and realize the full potential of this technique. Investing in high-quality filters may seem high at first, but it pays off as it ensures that the filters do not become a limiting factor.
I have been photographing with filters since 2008 and have tried out various manufacturers. During this time, filter technology has developed considerably. In the past, ND filters often had strong color casts, and in most cases they were made of solid-colored glass, which led to darker corners in wide-angle shots. Nowadays, the filters are coated very thinly, which avoids this effect.
In my recommendations, I divide the application into two groups: Those who only want to take long exposures and those who also shoot at sunrise or sunset. For the former, screw-in filters are sufficient, while the latter should invest in a filter system with a filter holder and slide-in filters.
Screw-on Filter
A screw-on ND filter is a simple solution, and I recommend the “Holy Trinity” set with the strengths ND 8 (0.9), ND64 (1.8) and ND 1000 (3.0). Alternatively, you can also use the ND Circular ND Filter Kit. In addition to the ND 8 (0.9) and ND 1000 (3.0), you will also receive an ND 64 (1.8) + CPL, a cleaning cloth and a NiSi circular filter bag for optimum protection.
The advantages and disadvantages of screw-in filters are:
+ relatively space-saving
+ relatively inexpensive
+ quick to use
- limited use (no graduated filters)
Which filter diameter?
The filter diameter should correspond to the largest diameter of your lenses. If necessary, you can adapt smaller lenses with “Step Up Rings”. A step-up ring then has a large internal thread for your filter on one side and a smaller external thread for your lens on the other. However, make sure you use high-quality step-up rings to save space and quality. NiSi has the ideal range here.
The filter labels
When dealing with ND filters, you quickly come across different designations for the filter strength. One manufacturer may use ND0.9, another 8X, and yet another ND8X. I would like to try and clear up the confusion a little.
The simplest representation is the filter factor, which is given as 8X, for example. This means that it extends the exposure time by a factor of eight, regardless of the ambient brightness. For example, if the exposure time without a filter is 1/1000s, it is extended to 1/125s with an 8X filter.
Of course, the whole thing is too simple, so physicists invented the logarithmic attenuation scale. These markings are typical for ND filters, such as “ND0.9”. The “ND” stands for “neutral density”. Although in my opinion this is the most correct and important labeling - pure physics - I don't want to go into it too much. If you are interested, I recommend the Wikipedia article on neutral density filters. In short: A simple glass pane has a filter factor of 1 (i.e. no extension), which corresponds to an ND value of 0.
A filter factor of 2 corresponds to ND0.3, and each further doubling of the factor leads to an addition of 0.3. This may sound more complicated than it is, so I have attached a table with the relationships to illustrate this. You don't necessarily have to understand it completely, but it helps to have seen it once, especially if you screw two ND filters together.
Combining ND filters
It is possible to combine ND filters, but be aware that this can affect the image quality. But let's leave that aside for a moment. Now comes the question: how do I add the filters together? If I have a 1000X filter and an 8X filter. What is the result? 1008X? or 8000X? Again, it depends on which filter designation you use. Because one is added, the other is multiplied. In the above example with the filter factor X, you only have to multiply both values. So the 8X and 1000X filter becomes an 8000X filter. However, if you use the ND designation, you have to add them together. So an ND0.9 (8x) and an ND1.8 (64x) result in ND2.7. And then take a look at the table above: this is a 512X filter. (8x64=512). You don't need this every day, but it's good to have read it. I never combine ND filters, I just have a few more filter strengths that cover the ranges.
The Filter System with Slide-in Filters
A filter system offers a far more professional solution compared to screw-in filters. Here you have the option of using square ND filters as well as rectangular graduated filters, which allows you to control the contrast range, especially in light conditions during sunrise and sunset. The filter system consists of a holder that is attached to the lens with an adapter ring. The gray filters and graduated filters are slid into the clamping rails of the holder. When using several filters at the same time, it is practical to be able to change each filter individually without dismantling the entire system. However, the main benefit of a filter system lies in the use of graduated filters (GND filters), which must be movable in order to adapt the gradient to the respective situation. Round screw-in filters as graduated filters make no sense, as the gradient cannot be moved and the image composition is heavily dependent on the filter.
I personally use the NiSi V7 holder, which is designed for the 100mm system. This system is suitable for lens diameters up to 82mm (with adapter ring up to 95mm) and can even be used with slight restrictions up to a focal length of 14mm. The limitations are that the holder must be aligned very precisely at 14mm in landscape format, otherwise the filter clamps will be visible in the corners of the image. This problem does not occur in portrait format. I use the NiSi V7 holder on the Canon R5 with the RF 14-35mm lens. The holder offers space for three slide-in filters, and a polarizing filter (CPL) can also be used in the adapter ring. This can be precisely adjusted to requirements using small adjusting wheels when installed.
The selection of ND filters for a filter system is identical to the screw-in filters mentioned in the article above. I would recommend at least the ND Long Exposure Kit with 3 filters. If you prefer longer exposure times, you can use the ND Extreme Kit with 4 filters. Please note that this kit does not include a filter holder. Ultimately, you have to weigh up whether it makes more sense to buy individual filters or sets and, if necessary, supplement them with individual filters.
Advantages and disadvantages of a filter system:
+ Very versatile
- Very expensive
- Significantly more space required in the rucksack
Why use graduated filters at all?
The basic purpose of a graduated filter is to reduce the dynamic range of the scene to a level that is acceptable for the camera. Many people are familiar with this phenomenon: either the foreground is well exposed but the sky is almost overexposed, or the sky is optimally exposed but the foreground is too dark. This is due to the contrast range of the scene, which is simply too large for the camera sensor. Graduated filters are used to compensate for these two extremes.
Some may argue that this is also possible in Photoshop. Yes, of course it can. You can take two exposures and then combine them in Photoshop with luminance masks or in Lightroom as HDR. In terms of cost, this is definitely the cheaper solution. However, it requires you to sit down and edit each shot. You also need a certain amount of imagination on location. With a filter, on the other hand, the image is already largely created in the camera.
A common counter-argument is: “I edit this in Photoshop because the gradient darkens objects.” This objection is correct, but in many cases it is not as problematic as is often claimed. For example, if a hard gradient runs through a shady mountain, this is understandably challenging. In such cases, it might make more sense to work with two exposures. However, there are many situations where I place the gradient filter right through the subject and it's not even noticeable. Certainly, slight adjustments may have to be made in Lightroom, but this is limited. Both approaches lead to the goal, and neither is fundamentally right or wrong.
Which graduated filters?
The recommendation for graduated filters is more difficult than that for ND filters, as there is no real “universal filter” that you can start with without any problems. A graduated filter that is perfect in one situation may not be at all suitable in another. There are graduated filters in different shapes (soft, medium, hard, reverse) and also in different strengths.
It can all be quite confusing.
Let me shed some light on the different types of graduated filters.
Soft Filter
A soft filter is characterized by an extremely gentle gradient. It starts at the top with its specified filter strength and gradually reduces this to the middle of the glass. This filter is ideal for gently darkening the sky, especially if there are large obstacles in the image. I often use the Soft Filter in combination with another filter to slightly optimize the histogram.
Medium Filter
Similar to the soft filter, the medium filter starts at the top with its specified strength. However, the gradient is limited to a slightly smaller area. I use this filter, for example, by placing it on the horizon and possibly moving it slightly below it. This is a good way of limiting the effects of the sun on the water. Medium and soft filters are of course very similar, whereby the effects of the gradient are more visible or more quickly with a medium filter than with a soft filter.
Hard Filter
The filter with the hard gradient is completely dark in the upper half, with the very hard gradient only occurring at around 5-10 mm on the glass. It is particularly useful at sunrise and sunset, where there is a significant difference in brightness between the sky and the foreground. A straight horizon is an advantage here, as objects or small hills are darkened considerably. However, work here must be extremely precise. A slightly incorrectly positioned hard gradient is often immediately visible in the image. If it is too low, for example, the water on the horizon will be quite dark.
Reverse Filter
The most striking filter is definitely the reverse filter, as it reverses the gradient a little. It has a similar structure to a filter with a hard gradient, but with a special feature: it gently becomes a little brighter again above the hard gradient. Reverse filters are the latest on the market, as they were not feasible in the past. Some manufacturers used to immerse the filters in a bath by hand to create the gradient. This was not possible with Reverse. Only new production methods have made the manufacture of reverse filters possible. The reverse filter is the ideal filter at sunrise and sunset. Shortly before sunrise or shortly after sunset, when the sun is below the horizon, the sky is very bright. If you were to darken the sky with a hard filter so that the brightest area fits, the sky further up would often be too dark. This is where the reverse is just right. It darkens where it is brightest and the sky further up is darkened less. Like the Hard Filter, the Reverse Filter is very fussy when it comes to positioning. Incorrect positioning is immediately noticeable.
And what strengths do I need now?
The darkening strengths are not so easy to recommend because, as always, it depends. While I need a less strong filter here in moderate light, the bright sunset in Spain may require a stronger filter. The foreground also plays a role here; the bright beach is a little closer to the sky than the dark foreground on Lanzarote. Fortunately, however, you can help yourself a little. If the reverse filter is a little too weak, you can optimize the histogram a little by inserting a soft filter and moving the histogram to its perfect position.
So, we’re still not much further along: which filters should it be then? Yes, I admit, I also have a hard time recommending something. Over time, I’ve bought almost all the filters NiSi offers, except for one GND gradient filter, all based on the feeling of ‘better to have them than to need them.’ But it’s not enough to just tell you ‘buy them all, you’ll need them.’ However, I know plenty of people who only use a handful of filters.
Since I’ve been indicating which filters I’ve used in my photos on YouTube and Facebook for some time now, I decided to create a table. The result is quite clear. There are 4-5 filters that dominate by far, others fall into the middle range, and there are even filters that I hardly ever use. For this reason, I don’t own the 1.5 Soft, for example, because I hardly ever use the 1.2 Soft.
If you take a look at this table, it will definitely make things a lot clearer, right? It would definitely be worth starting with just 3-4 filters. Or you can start with just one. However, this table only tells half the story because I’ve expanded it. In the upper table, it might look like I used the 0.9 Soft filter for 35 images. But I often combine filters. For example, of the 37 images with the 0.9 Soft, 11 were made in combination with the 0.9 Reverse. So, if you buy the 0.9 Soft, it’s best to get the 0.9 Reverse as well. As I mentioned earlier, I often use one filter for the ‘rough,’ and the Soft filter is then inserted from above until the histogram on the camera is optimal.
