It is convenient to shoot at a short shutter speed: and the “gear” from the trembling of the camera will not be in the hands, and the rapid movement in the frame will be able to “freeze”. There are times when the shutter speed needs to be lengthened, but it is impossible to do this because of too bright lighting. Consider two situations for example.
Let’s say you shoot on a sunny day on a light-strong fix-lens, say, on Nikon AF-S 50mm f/1.4G Nikkor. And you want to shoot it on the open diaphragm to get the most blurry background, beautiful bokeh. But even at the shortest shutter speed available to your camera (1/8000 s or 1/4000 s), and at the lowest ISO, the frame still turns out to be overlit. It is necessary to somehow limit the light flux to be able to shoot at longer speeds without overlight. The same problem will arise when shooting in a studio with pulsed light: rarely what flash will reduce its power to be able to work on an open aperture.
Or, suppose you want to get a blurred motion effect, for example, when shooting a landscape or street sketches, which looks very interesting. You can wash everything from sea surf and mountain waterfalls, ending walking people. So, to maximize the shutter speed, you closed the diaphragm (say, to F22), reduced to a minimum ISO, but it still does not get long enough.
What should we do in such situations? To solve them, neutral gray filters or ND-filters (Neutral Density) have been created. In fact, it’s just a darkened glass that is installed on the lens. Neutral-gray this class of filters is called because they should not distort the color rendering in our pictures. This is not a simple, but a very high quality darkened glass.One of the important advantages of the advanced Nikon cameras (Nikon D800, Nikon D810, Nikon D850, Nikon Z 7) is the basic ISO 64 and the ability to reduce the sensitivity to ISO 32. Therefore, with such cameras sometimes do not need ND-filters: lengthen the shutter speed is a simple decrease in sensitivity. For example: ISO 64 adds almost 1 step to the exposure compared to ISO100, which is already a lot — the shutter speed will be almost 2 times longer!
An alternative to the use of ND-filters is a special technique of shooting and processing. However, neutral gray filters still give a more organic result, and there is no need to waste time processing the image.
Neutral gray filters are available in various form factors. Let’s consider the two main ones. The most common look is the usual round threaded filters, screwed on the lens. Here the main thing is to choose a filter for the diameter of the thread of your lens.
The second type is rectangular system filters. The point is that the photographer, thanks to a special holder, can insert into it any necessary filters for work. First of all, such a system is designed to use gradient filters designed to equalize exposure in landscape frames and protect the sky from overlights. But solid neutral gray filters there can be used quite freely. This system is good for its versatility — you don’t have to buy new filters if you change the lens to a new one with a different thread diameter. The most common size of rectangular system filters is 100 mm wide and 2 mm thick. There are many filters and holders of this format on the market, but filters of other types are almost exotic.
For wide-angle optics with massive front lenses that do not provide for the installation of conventional threaded filters (e.g. Nikon AF-S NIKKOR 14-24mm f/2.8G ED), system filters are available with a width of 150—165 mm and special adapters for a specific lens model. Unfortunately, such systems are expensive, and in use and transportation too cumbersome.
At the same time, for lenses with smaller dimensions of the front lens, 100 mm wide filters will suffice. For example, Nikon Z’s line of mirrorless optics has a Nikkor Z 14-30mm F/4 S lens. This is the first full-frame lens with a focal length of 14 mm, which allows the use of conventional threaded filters with a diameter of 82 mm, as well as works without dimming at the edges with system 100 mm light filters. The possibility of using relatively inexpensive and compact 82-mm round and 100-mm system filters is the most important practical advantage of this lens!
Whatever form factor of light filters you choose, they will work the same way. All neutral gray filters differ in their density, that is, the degree of dimming. Several different labels are used in the world to characterize the density of the ND filter.
Table. Neutral filter density and dimming rate
The density of the ND filter is characterized by how many times the flow of light passes through it. This is the most common scale in everyday life. It is her readings that are usually indicated after the ND marking: ND2, ND4, ND16… And if you, let’s say, took an ND8 light filter, it means that your filter has extended exposure by 3 steps. Note that starting with the ND512 density, the values given in the label on the filter start rounding. So, the ND1000 filter actually reduces the luminous flux by 1024 times. In the table we give both the actual and (in parentheses) the rounded value that will be specified on the filter itself.
An alternative measurement scale is a traditional density scale. Such a scale can often be found on system light filters-plates, but it rarely uses in practice as the main one. We brought her in for the completeness of the picture. The ND8 filter has a density of 0.9 units, and ND1000 has a density of 3 units. Given here and the proportion of the luminous flux that passes through a particular filter, in percentage. See how little light passes through the densest ND filters! Less than a percentage!
By the way, many manufacturers do not dwell on ND1000 values and produce much denser filters. So, on the market there are light filters that will give many hours of exposure even on bright sunny day, for example ND32000 (15 EV) and ND16777216 (24 EV). For the manufacturer, the creation of such a dark, but having a good resolution neutral filter is a kind of achievement, so such dense filters are available in the lineup of only the most advanced brands.
A polarization filter can be used as a replacement for the neutral gray filter. Any polarization filter “eats” about two stages of exposure, which means equivalent to the ND4 filter. In the case of shooting on light-intensity optics with bright lighting “polaric” may be even more preferable. After all, it will help to remove from the image excess glare, which is necessary when portrait photo shoots in the city. By the way, high-quality polarization filters you can buy it from amazon.
Which neutral gray filter to choose?
As for the brand of the manufacturer – here the main thing to understand that a good filter will not cost cheap. Cheap filters from Chinese trading platforms significantly distort colors, have uneven dimming and worsen the detail of the picture. So, if you choose the ND-filter, then from a well-known brand with a good reputation. There are many such on the market: Hoya, Formatt Hitech, B+W, Marumi. System filters made of optical glass are produced under the brands Formatt Hitech, Nisi, Haida. Plastic (they have lower price, but lower optical properties) — Lee, Cokin. Note that in the case of system filters 100 mm wide and 2 mm thick it is possible to combine anchorages of one firm and filters of another – the filters themselves are standard.
What density filter to choose?
There are no universal solutions. But, perhaps, the most popular filter will be ND8 – it, for example, will allow to shoot in the evening city at shutter speeds of about 30 seconds, getting spectacularly blurred lights from moving transport. The same filter will make it possible to shoot light-strong optics in dazzling sunlight without getting too bright frames. For example, if without the filter shutter speed was 1/8000 s, then with the ND8 filter, we will get the same image brightness at 1/1000 s.
It also allows you to take exposure in the area of ½ s during the day shooting of waterfalls. At the exposures about -1 with the water in a stormy stream does not turn into “milk” yet and retains a pleasant texture.
ND64 light filters will allow to shoot at shutters of the order of 30-60 s in the mode time. This is useful, for example, for photographing the water surface, moving clouds.
The ND1000 filter is already extremely long exposure. With it excerpts will be about 30 seconds at bright noon and about 2-15 minutes in mode time. Personally, I use it not so often, only when it is necessary to strongly blur weak movement (clouds, for example). In addition, ND1000 or more dense filters are suitable for shooting a solar eclipse — without a very dark filter, the open sun is dangerous for both the eyes and the camera.
It is worth mentioning about neutral gray light filters of variable density. This filter can be twisted in the frame, thereby adjusting the degree of blackout. Technically, a variable density filter is two polarizing filters set to each other “face”. If you have two “polarics” in the farm, you can make such a filter with your own hands. However, the ND-filter of variable density also inherits all the nuances of polarization filters, namely, uneven darkening of the frame when used with wide-angle optics.
In addition, when applied, it is impossible to accurately set the required density. And if it is impossible to adjust the variable ND-filter to a specific value, it will not be possible to accurately recalculate the exposure for shooting with it.
Specificity of shooting with dense ND filters
With density filters up to ND16—ND64 (depending on camera and lighting conditions), the camera autofocus and exposure will work as usual. You can just twist the filter and continue shooting. But with darker filters, there may be problems. Since they miss very little light, the autofocus may stop working, the expozamer will be wrong. Therefore, with ND1000 type filters, a special algorithm of actions is required.
- If you are using a protective light filter, it is better to remove it before installing the ND filter. And in general, the fewer filters on the lens, the better the result will be. In addition, several threaded filters installed on each other can cause vignetting on wide-angle optics.
- It is necessary to use a tripod, and the frame must be pre-arranged.
- If you have autofocus, focus on the subject, then turn off autofocus with the tumbler on the lens.
- Time to make a test frame without filter to check exposure. If the brightness frame suits us, there are no overlights and dips in black, remember the parameters of shutter speed, diaphragm and ISO, at which the picture was obtained. The shooting of the test frame can be replaced by viewing the image in Live view with exposure emulation – the screen will show the correct brightness of the frame before shooting.
- It is necessary to recalculate the exposure to the light filter used by us. To do this, you can use a special application – an exposition calculator, which will lower it by a proper number of steps. All you need is to add the original exposure to the program (without a filter) and set the density of the filter used. It remains to adjust the resulting long shutter speed on the camera.
- If the shooting is conducted on a mirror camera, it will be useful to close the optical viewfinder something, as the light that gets on the matrix through it, can cause light illumination. In advanced Nikon devices, there is a built-in viewfinder flapper for this. If not, the camera and viewfinder window can be covered with an opaque cloth on top.
- Now, when the camera is fixed on the tripod, the frame is assembled, focused, and the exposure is calculated, install a filter.
How to make shutter time longer than 30 seconds
Modern cameras allow you to automatically practice shutter speeds up to 30 seconds. What to do if it is necessary to shoot at shutter speeds even longer? Let’s say we use an ND1000 filter and shutter takes 2 minutes. How do I get it?
Nikon cameras have 2 modes when setting shutter speed. The first is Bulb: the shutter takes place while we hold the descent button pressed. This mode is not suitable for the most obvious decision – to hold the release button with your hand and take off. The camera will be transmitted to the trembling of your hands, the footage will be lubricated. Bulb mode is used to work with remote controls. Simple one-button consoles assume that you will track the time on any available clock and keep the button on the remote for the right time. Programmable consoles are more convenient — you can set the required shutter time directly on them.
Bulb and Time modes are available to the photographer in M mode (manual). Simply twist the shutter wheel towards their lengthening: after the value of 30 s, these modes will go.
Time mode is more convenient for shooting without a remote control. In this case, shutter speed starts at the first click and ends at the second time. It turns out that during shooting you do not have to keep the descent button pressed constantly, and the right time can be measured by the stopwatch smartphone. Especially as ideal accuracy when working with shutter speeds more than a minute is not required, plus or minus a couple of seconds will not solve anything.
Long exposure is a powerful tool in creative photography. With their help, you can show the movement in different ways in the frame, demonstrate not only the dynamics, but also the flow of time, and their use is limited only by the imagination of the photographer. ND-filters will allow you to achieve really long excerpts and get unusual frames.