Filters commonly used in digital photography

In the film age, filters are essential for professional photographers. There are many kinds and rich effects. Different from modern photoshop digital post-technology, photographers must rely on auxiliary front-end equipment to control the color, effect and light of the picture. This also leads to the photographer's important feature is the vest shawl, which is mostly filled with filters. After digital photography became the mainstream, filters gradually faded out of photography. Nevertheless, it is really a great pleasure to enjoy the pleasure you can get in the early stage of creation, especially the digital camera has real-time display function. That's a little far.

For digital cameras, besides UV mirrors, what other conventional filters or necessary filters exist? This is worth talking about. Photoshop7.0 version 7.0 has the following interface display at startup.

The filter full of human eyes was once a necessary polarization for landscape photographers. Photoshop can indeed use technical means to darken the sky, enhance the blue tone and eliminate the reflection, but compared with the previous filtering of harmful light, the means in the later digital stage are much more complicated, and the control of picture details is not easy to keep. Polarizer is a traditional filter for digital photography. Landscape photography uses it to darken the excessive polarized light in the sky and make the blue sky bluer without overexposure. The polarizer does not change the spectral components of visible light, and only filters out polarized light.

It is only one of the functions of polarizer to darken the sky and enhance the blue color. The surface reflection of nonmetallic materials is polarized light, such as shooting through glass and water, which will become harmful light that interferes with imaging. Turn the lens of the polarizer and you can see the change of the picture in the viewfinder. In addition, the polarizer can also improve the saturation of the ground scene. Let the subject under strong light become clearer.

Especially when shooting through water or glass, the problem that polarized light interferes with imaging can't be solved by photoshop unless you draw one on it. For landscape photography and portrait photography with sky, polarizer is a necessary conventional mirror. It is worth mentioning that the polarization displayed on the PS7.0 startup interface is PL and linear polarization. The common polarizer on the market is cpl circular polarization. The difference between them in application is that linear polarization can be used in multiple pieces, while circular polarization can only be used in one piece at a time. Modern digital SLR cameras have autofocus function, and linear polarization will lead to focusing error, while compact cameras need polarized light provided by the lens to illuminate the night view finder, and circular polarization has become the mainstream. Optical principles are not explained here.

In addition to circular polarization, gray gradient and medium gray mirror are also necessary accessories for landscape photography. Silhouette photography is simple and abstract, but you don't need it all the time. The light ratio between the sky and the ground is so large that it is impossible to keep the details of both sides through one exposure. In addition to taking two photos with photoshop for post-synthesis, you can only use gray gradient. Moreover, we all know that the late PS synthesis needs to carefully control the shooting point and composition range, and the discovery rate is extremely high.

The upper part of the gray gradient absorbs light in the same proportion without changing the spectral composition. All it does is balance the light ratio between the upper and lower parts (you can't balance the left and right), and meet the synchronous preservation of details through almost uniform exposure. The word "gradient" has a more detailed division of filters, including hard gradient, soft gradient and split mirror. Hard gradient and split mirror are suitable for the situation that the light ratio is directly divided by the horizontal line, while soft gradient is suitable for conventional shooting. The latter has high application frequency and small filter trace.

Compared with the excessive shading of gray gradations, the grey mirror in the middle blocks the light as a whole. There is no selective absorption of incident light. In the era of mechanical cameras, the shutter speed is difficult to exceed 1000, and it is very demanding to use a large aperture to achieve a small depth of field under strong light. Medium gray mirror (called subtractive mirror) solves this problem. Of course, for modern cameras, the shutter speed has exceeded 1/4000 seconds, so it seems meaningless for grey mirror to achieve a large aperture. However, in the studio of flash photography, the advantage of realizing small depth of field under strong light is still reflected. (Note: In studio flash photography, the shutter cannot be controlled left and right. )

Today, we use more medium-gray mirrors to achieve elegant slow-door photography. Water flow, people flow, satellite orbit (digital cameras are prohibited in satellite orbit celestial photography).

In addition to the difference of aperture, grey mirror also has classification. According to the light blocking ability, the filter factors are divided into ND2, ND4, ND8, ND 16 and ND32? Can you expand 1 times, 2 times and 3 times respectively? Shutter time, it should be noted that the medium gray mirror with high transmittance will lead to the failure of autofocus function. When you use it, you can focus on the composition first, and then install a filter to re-measure the light.

Together with UV mirror, circular polarization, gray gradient and medium gray mirror are the common filters that digital cameras must have, and the photo effect and photography technology they can bring can not be replaced by digital post-technology