ND (Neutral Density) filters are one of the most used tools in landscape photography, architecture and more. They meet creative and technical needs thanks to their ability to filter light without adding colour cast and allow the photographer to manage the amount of light that hits the sensor. In this article, we will see in detail what ND filters are for (with a focus on ND1000 filters), which ones to choose, which are the different formats on the market and why not all ND filters are the same.
What are the 10 Stop ND1000 filters for?
ND filters are very useful for long exposures (long exposure guide), and in those situations where we want to obtain a certain shutter speed but we cannot set the aperture and ISO value at will. Let’s make two examples in two very different situations:
First scenario: we are taking a photo of a landscape or architecture outdoors and we have set the aperture to f/11. We know what we need and we know that the quality of the lens at f/11 is almost optimal and at the focal length that we are shooting we’ll have everything in focus as desired (see focus in the landscape). The ISO sensitivity is set to “native” (or “base ISO”, we don’t want to reduce the dynamic range and increase the noise, but we want the maximum amount of information that the sensor can record (read more about dynamic range). At this point only the shutter speed remains a variable so we must set a time that allows a correct exposure.
The photographer, however, may have other creative choices in mind for shooting, he may want to shoot 1/2″ to capture a slight movement in the waves, or for 2 minutes to record the moving clouds or even shoot for 10 minutes or more to get an architectural shot without the presence of people. At this point, ND filters are mandatory, with a neutral density filter we can compensate the light and choose the shutter speed we prefer.
The ND1000 will probably be used to achieve shutter speeds of several seconds or minutes (depending on the ambient light), if you only want to lengthen the time slightly, you can choose an ND8 filter (3 stops). If your goal is to take long exposures during the day, it is better to focus on filters 15 or 20 stops, as detailed in this article on daytime long exposures.
Second scenario: a different type of situation can arise in the case of photos taken in broad daylight where a wide aperture is required. Let’s imagine a portrait photo where the photographer wants to keep a very open aperture (f/2.8 or wider) to control the depth of field. If the light is too bright and the shutter cannot be fast enough (most cameras are limited to 1/4000″or 1/8000″) the shot will be overexposed. An ND filter allows you to reduce the amount of light that hits the sensor and therefore to shoot with a wide-open aperture even in very strong light. In this case, an ND8 filter (3 stops) is most likely sufficient.
Here the NiSi 10 stop ND1000 filter 100×100 allowed the photographer to lengthen the shutter speed for more than 1 minute and capture both the movement of the water and clouds.
In this shot a 3 Stop ND8 filter was used, the lower density of the ND8 compared to the ND1000 was chosen to use a shutter speed of about 2 seconds, necessary to capture a slight movement of the waves.
In the above examples, we’ve seen 3-stop and 10-stop filters, the main difference is that the ND1000 (10-stop) filter blocks much more light than the 3-stop filter, thus appearing darker to the eye. There are several terms to refer to these filters: the term “ND1000″ refers to the fraction of light let through by the filter, which in this case is 1/1000th. When we refer to “Stop” we mean that the filter halves the light 10 times, in the case of an ND1000 filter, 10 absorbed stops.
On the other hand, when we hear about “ND 3.0” (not to be confused with 3 stops filters, that are “0.9”) we are considering the base 10 logarithm of the absorption factor, if a filter halves the light, the absorption factor is 2. The base 10 logarithm of 2 is 0.3. For a 10 stop filter: the base 10 logarithm of 210 is 3.0. Keep in mind that each stop you add is 0.3 when using the “Optical Density Number” referring to a ND filter.
If we call an ND8 a 3 stop filter, then an ND4 and ND2 will be 2 and 1 stop filters respectively. If we talk about ND16, ND32 and ND64 filters we are considering 4, 5, and 6 stop filters. Moving up on the scale (ND128: 7 stops, ND256: 8 stops, ND512: 9 stops, etc.) the 10 stop filter should correspond to ND1024, but for simplicity we refer to it as ND1000. Below you will find a conversion table for ND filters.
|Stop||Density ND||Absorption factor||Resulting shutter speed (if 1″ without filter)|
Which ND1000 filter to choose?
Being among the most popular filters in photography, we find different solutions on the market, both as regards the materials used and formats. Let’s see the substantial differences between ND1000 screw-in filters and square ND1000 filters and how to be sure to take into consideration the most important aspects of these two categories.
10 Stop screw-in filters
Screw-in filters are cheaper than square filters because they use less glass. These filters are mounted in a metal frame (or plastic if very cheap) and they screw directly onto the front thread of the lens. To consider for a 10-stop screw-in filter:
- The type of glass used, not all glass is the same, the lens grade optical glass used by NiSi is our exclusive and it’s usually used only for the most important elements of a lens (for example ED elements – extra-low dispersion, with very low dispersion).
- Coatings (Nano-Coating, IR, Anti-glare, etc.) applied as a treatment to the glass.
- The material of the filter frame, which on the cheaper ones can be plastic or cheap metal alloys.
- The thickness of the filter frame, a thin frame reduces the lateral light fall (vignetting)
NiSi offers ND1000 screw filters in lens grade optical glass with IR treatment, anti-reflection and Nano Coating.
The circular filters screw directly onto the lens, but if you have several lenses you must use step-up rings (which can introduce mechanical vignetting) or you must have a filter for each lens of a different front diameter. If our goal is to start with ND filters, circular could be the right choice, given the lower costs, but we must know the limits. Especially in regard to the difficulty to combine a screw-in ND with other important filters such as the polariser and graduated filters (GND).
ND1000 square filters
The ND1000 square filters are squares (or rectangles) of optical glass which are inserted into slots (filter holder). These filters are much more versatile than the screw-in ones for various reasons, including the possibility of being mounted on lenses without thread (through special holders). You also do not need a filter for each diameter of the threads of your lenses and you can “stack” several filters together, such as ND1000 + GND + Polariser. In square filters, the same points taken into consideration to evaluate the screw filters are valid, but the choices of glass quality and the coatings are more critical. Given the higher cost of professional optical glass, many manufacturers aim for lower quality glass, no coating or use optically treated resins that do not guarantee satisfactory and uniform optical quality. The use of glass and resins leads to decrease in the transmitted light and reduce the sharpness of a lens. For this reason it is important that all the elements of our optical system are of the highest quality, read this in-depth analysis on the quality of optical glasses. Some key filters coatings are:
- Anti-glare coating, essential to avoid ghost effects, flares and internal reflections.
- IR coating to block the infrared component of the light, this is invisible to the human eye but the camera sensor captures it, adding a magenta dominant to the shots.
- Nano Coating, which greatly increases the resistance to water and grease (naturally present on the skin) of the glass and therefore facilitates cleaning outdoor, even in the rain.
ND1000 filters can be a fundamental creative tools for landscape photographers and not only, but it is important to know them well and use quality filters on well-designed systems. NiSi offers V6 and V5 PRO holders for 100mm wide filters, with adapter rings and polariser included in the kit and no vignetting even at 16/17mm on full-frame cameras. The V6 and V5 PRO are equipped with 100mm ND filters, available in 10 stops and in many more densities.