How do you get beautiful night shots and a clear starry sky despite light pollution?
Nocturnal landscape shots or breathtaking city shots of a skyline and on top of that an impressive night sky and maybe even the Milky Way in the background. But the light sources of our big cities, industrial plants and airports create a phenomenon that is increasingly reaching rural areas near cities. For every photographer who has ever dealt with astrophotography and night photography, light pollution (also light smog or light pollution) is a topic.
This reduces the contrast between celestial objects and the night sky illuminated by artificial light sources. The background is that the artificial light radiates into the atmosphere.
Thus, night shots of a landscape or city often show a yellow line of color and the starry sky appears only dark. The multitude of stars is therefore no longer visible. Actually the night sky is dark blue and cool. But due to the light smog it becomes a cloudy grey fog. Artificial light sources include street lighting, video walls, neon signs, floodlights and industrial lighting. The main problem is the light wavelengths 590 nm, 545 nm and 580 nm.
The Neutral Night Filter from Kase is an Astroklar filter and is also called Light Pollution Filter or Night Light Filter. The aim of using a light pollution filter is to give the night sky back its cool darkness and to remove the typical yellow tint from night shots. In rural areas the Astroklar filter can also improve the photography of the starry sky by increasing the contrast between night sky and stars, which is reduced by light smog. This allows you to create clear images of the starry sky and natural city and landscape photographs with nighttime "cold" without yellowing.
The higher quality images also make post-processing easier, as you can achieve better contrasts and expose longer where you previously had to stop down without a filter due to light smog caused by the disturbing light.
What can the Neutral Night Filters be used for?
Clearly primarily for use in night landscape and astrophotography. By using our Neutral Night Filters your images will achieve more detail and a much clearer and higher contrast image of stars and astronomical deep sky objects. Our Astro Filter reduces the light incidence by about 2/3 aperture.
Did you know that even a city with 25,000 inhabitants is enough to artificially brighten up the surrounding area within a radius of 20 kilometres, making the night sky appear duller and less contrasty, or to give night shots a yellow tint? The artificial light sources that cause the greatest light pollution are sodium vapour lamps (light wavelength of approx. 590 nm) and mercury vapour lamps (light wavelengths of 545 nm and 580 nm). These wavelengths, among others, are blocked by our night light filters and thus enable us to take pictures of starry skies and night shots without yellowing. But how exactly do the filters work against light pollution?
What can the use of such a filter bring?
- The filters filter the light that enters the camera from the sky. Therefore, with filters less light reaches the sensor. Therefore you have to set a higher exposure time with filter than without.
- The objects are displayed darker with the filter.
- A filter can enhance the contrast of certain object types.
- A Neutral Night Filter suppresses stray light.
How do the Astro filters of Kase Filter work?
In order to understand how accurately the night light filters of the Astroklar series work and how they facilitate astrophotography and night photography, one must understand how exactly the so-called light bells are created. The part of the artificial light that is radiated upwards into the atmosphere reflects again on the atmospheric layers, like atmospheric dust and water, and is thus widely dispersed. This creates the so-called light bell, because the air is brightened and light penetrates it. A city with about 25,000 inhabitants is enough to brighten the sky within a radius of about 20 kilometers and thus to disturb astrophotography and city and landscape photography at night by light pollution. It is therefore a side effect of industrialization.
The biggest producers of light pollution are industrial plants, big cities and highly directional spotlights from airports or high beam from cars and light art like skybeamers and laser shows. This light smog then envelops nocturnal motives like a kind of veil, so that the natural night light appears yellowish, thus reducing the visibility of stars.
Our Astroklar filters are specially coated so that almost all light waves of the entire colour spectrum can pass through and mainly the yellow and orange light wavelengths are blocked. This prevents the unwanted wavelengths from reaching the camera's sensor. The resulting cleaning of the light waves provides for more detailed images with considerably more brilliance and structure, especially in nighttime city and landscape photography or astrophotography.
How do I use Astroklar filters in photography?
- Set up the tripod, attach the camera and install the remote shutter release
- Selecting the desired subject & cropping
- Set the manual white balance of the camera to 3600K for example
- If necessary, counteract cooler color temperature by increasing the white balance by +700K to +1500K
- Screw on filters: Screw the Neutral Night filters onto the camera.
- Slide-in filters: The holder for the 100mm and 150mm plug-in filter system can also be attached very easily. Afterwards, the Neutral Night rectangular filters can simply be pushed into the guide rail. Then rotate the filter holder so that you get the best possible shot on the photo motive.
- Set the exposure time and take the picture with the remote shutter release
This is what distinguishes the Astroklar filters from Kase
The multiple coating
Both the screw filters and the rectangular filters for the filter holder have the same coating. Another big advantage for astrophotography is that our Kase nightlight filters are neutral, especially in the IR light range.
The nano coating on both sides
Both filter types also have a special nano-coating, which not only prevents reflections, but is also water, oil and dirt repellent. This also ensures that the filter glass can be cleaned very easily.
Astro Filter as round filter or as rectangular filter?
This depends primarily on personal preferences. The main difference is the possibility of combining different filters. For example, you can integrate a CPL filter in the 100mm filter holder for our plug-in systems and combine it with your plug-in filters. For clear and starry night skies, as well as night photography with more details and structure without yellow-orange light pollution, all our Neutral Night Filters can be used.
Advantages Kase Astro rectangular filter:
- Different filters can be combined more easily
- magnetic CPL polarizing filter can be integrated into the 100mm filter holder
- Foam cover protects against light incidence between holder and filter with the additional use of ND filter
Advantages Kase Astro round filter:
- Can be screwed directly onto the optics
- Much lighter in weight
- Light-tight seal between lens and filter
No matter whether in professional or hobby photography, everyone can use filters in round or square. Mostly the choice is decided by the general preference how you work with filters. Only with an Astro round filter, or combined as Neutral Night rectangular filter with a polarizing filter. In general: Especially when it comes to combining filters, this is usually easier to achieve with a plug-in filter system than with round filters. Here, filters can be inserted into the filter slots of the rectangular filter holder. This is especially helpful when using gradient filters, as the filter gradient can be adjusted according to the image composition.
What is the best way to photograph stars?
In order to be able to photograph faint stars or even the constellation of the Milky Way, a long exposure at high light sensitivity is necessary. This requires a camera that meets certain basic requirements. Both the ISO value and the exposure time must be manually adjustable. In addition, a Neutral Night Filter must be attached to the lens to avoid any stray light.
A tripod is also essential to prevent camera shake. When using it, care should be taken to deactivate or switch off any existing image stabilizer, as this only makes sense for exposure times down to about 1/8 second. With long time exposures the anti-shake feature will have the opposite effect. The camera tries to compensate for supposed but not existing movements and brings a certain blur into the picture.
The ISO value controls the light sensitivity of the image sensor. Remember that the attached filter reduces the light incidence by about 2/3 f-stop! The lower the light situation, the higher the ISO value should be. Here, one should first experiment a little in order to find out up to which ISO value an image is usable. In many common digital cameras, details often get muddy already at ISO 400, while in modern SLR cameras with big image sensors, even values around 1600 still provide good results.