Our combi filter: ND filter together with a CPL filter in Kase quality
The Kase magnetic combi filter is excellent to accompany you through a photo tour in the landscape. The combi filter consists of an ND8 filter combined with a circular polarising filter. Due to the longer exposure time, for example, the movement of clouds can be captured or water can be silkily drawn. The CPL filter integrated at the same time makes it easy to adjust the reflections in the water and the contrasts in the sky. This is because the polarising filter can be adjusted directly on the lens by turning it, independently of the ND filter.
The material used here from our Kase Wolverine series scores with its outstanding colour neutrality. This is supported by the high-precision optical glass used, which is also extremely shock-resistant. In addition, the filters are very easy to clean due to the oil- and water-repellent coating. The thread on the combi filter makes it easy to screw it onto the lens you are using. In addition, the magnetic ring on the filter allows you to mount other magnetic filters.
When should a polarising filter be used in photography?
Circular polarising filters are used in photography when reflections on non-metallic surfaces are to be prevented in order to direct the focus on the actual subject and to make the colours appear richer. This is particularly useful in landscape and architectural photography. The polarising filter is also frequently used when photographing products. Because there is still no image processing programme that can imitate the function of a polarising filter.
Furthermore, a CPL filter enhances the colours and contrasts of an image by filtering complementary polarised light, for example the reflected blue of the sky on the green of the leaves and grasses. This makes the colours of the object in focus look much richer. Likewise, a CPL filter enhances the contrast between the white clouds and the blue sky. When the polarising filter is rotated, it shows its function by turning the light waves as if through a kind of meat grinder. During this process, the result is directly visible in the viewfinder. Colours intensify, haze and reflections are reduced and the sky gets a clearer structure, as the clouds are clearly set off from the blue of the sky. Water surfaces become clear and almost completely transparent.
What are the differences between a circular polarising filter and a linear polarising filter?
While a circular polarising filter can be used on SLR cameras as well as on other cameras, linear polarising filters cannot be used on SLR cameras because their measuring technique can cause errors in the image. With CPL filters (circular polarisation filters), the polarising effect can only be seen in one intended direction; with linear filters, the effect can be observed through both sides.
Circular polarising filter
Linear polarising filter
Suitable for SLR cameras
Unsuitable for SLR cameras
Polarising effect in one direction only
Function in both directions
Can the polarising filter effect also be created in the post-processing of the photos?
As already mentioned above, the polarising filter effect is one of the few effects, along with that of an ND filter and an infrared filter, which cannot be created by post-processing with image editing programmes such as Photoshop. This is because the effect of a CPL filter is a physical effect that simply cannot be recreated. Also, the reflections can only be removed by very complex editing and even then usually not completely. For this reason we advise you to shoot directly with a CPL filter.
The integrated grey filter
Grey filters are often also called neutral density filters or ND filters. These are glass panes of optical quality. Depending on the filter system, they can be used as a disc or, as in the case of the combi filter, enclosed in a metal ring as a screw filter or magnetic filter.
When searching for the right grey filter, you will often come across a wide variety of designations. ND3.0, ND1000, ND64x, etc.. Mostly the neutral density or the extension factor to the exposure time is indicated. The following table shows the three most common grey filters and their different designations and effects.
Besides the different names, grey filters are offered in different sizes. The following applies here in principle:
For screw-in filters, the mm specification refers to the lens diameter.
for slide-in filters, the specification refers to the height and width of the filter and thus to the width of the slide-in filter holder system.
How do I calculate the correct exposure time with a grey filter?
As already mentioned, the length of the exposure time is related to the strength of the grey filter. So with an ND8 filter the exposure would be 8 times longer. For example, if the camera specifies 1/20 second as the correct exposure time, this becomes 50 seconds exposure when using an ND1000 grey filter.
It is also easy to use the aperture priority mode. You set the aperture yourself and the camera automatically calculates the appropriate exposure time. In most cases, modern cameras produce a very good result. For an architectural or landscape photo, you should usually use an aperture value between 9 and 11 in order to achieve the greatest possible depth of field.
If you want to take photos with an ND filter, you have to be able to set the shutter speed, ISO and aperture. This means that you should shoot in "M" mode, i.e. manual mode.
Areas of application of a grey filter
Grey filters are mostly used when you ...
- ... by means of the adjustable aperture cannot be darkened sufficiently to avoid overexposure of the picture
- ... want to blur movements by using the longest possible exposure time.
The first case usually occurs when you want to shoot with an open aperture to emphasise an object and the light is too bright. This can be the case, for example, when shooting at the beach. If the photographer would like to show the blue sky and the sea and the beach also reflects the light and the shutter speed cannot be set any faster.
In case two, you want to artificially lengthen the exposure time to achieve motion blur. This stylistic device is often used when photographing bodies of water, for example waterfalls or streams.
What tools are needed for long exposures with a grey filter?
For photographers, a flawless image is the be-all and end-all when taking pictures of buildings and landscapes. Good photographic equipment is indispensable to ensure that the desired motif looks its best later on. The following tools are particularly important:
- Remote shutter release
- Correction table for exposure time
Even when using the best tripod, it can happen that blurring occurs. However, this is often not due to an insufficiently firm stand, but to the mirror lock-up. For the perfect picture, it is important to avoid even the slightest shaking. To avoid this, the mirror lock-up can be set on SLR cameras.
When the mirror lock-up is activated, the mirror of the camera is raised. The mirror remains there. If the shutter release is then pressed for a shot, the vibration caused by the mirror folding up has already happened. Only the "curtain" of the camera is opened to take the picture, so that the folding of the mirror has no negative effect on the picture.