Lens Filter In Photography

Filter lens is a transparent glass or thin sheet of elements mounted in front of the filter. Filter lens is useful to protect the lens physics, change the characteristics of light passing through the lens or give special effects on the image.

Lens Filter Type - Based on How to Put It
There are two types of lens filters based on the way they are attached to the lens :

1. Screw In Filter (Ulir)

Filter screw in is a type of filter that is installed in front of the lens by following the existing thread on the front of the barrel lens. Each screw type filter has a specific size, following the existing thread size specification of the dilated lens. If there is a symbol of this diameter Ø then followed by a two digit number (72, 60 etc) then the two numbers indicate the size of the thread for the filter thread.

Threaded filters can be single or stacked in accordance with the visual aesthetics of the photo you want to achieve. 

2. Filter Slot In

For this type of lens filter, a thin metal frame where the filtered optical dfilter (usually called a holder) is attached to the adapter ring coming into the lens. The holder usually has three to four filter holder so we can stack some types of lenses. 

This type of slot filter is more flexible because it can be used for a variety of lens sizes and we can accumulate several types of lenses at once (CPL + ND for example).
  
Lens Filter Type - Based on Usage
There are many types and names of filters that are sorted by their usefulness. Below are some commonly used types :

1. UV Filters

UV filters (Ultra Violet) are transparent filters that are useful for blocking ultra violet light. UV filter's usefulness is to reduce the haze (thin smog) visible on the photo while still using the film. UV filters in the era of digital photography are not very necessary because ultra violet light does not affect digital sensors, just as if you were still using film.

But UV filters are still often offered by salespeople in camera stores and many who still wear them in the lens because of old habits that hard to die. Even if UV has no effect on digital sensors, at least this filter can be used to protect the front end of the lens from impact. Instead of my lens why-why, mending we sacrifice the filter. 

2. Polarization Filters / CPL

Polarizing filters are useful filters to darken the sky by increasing the contrast between the sky and the cloud. In addition, CPL filters are also useful for reducing the reflection of sunlight. Useful when photographing glass, reflective water and other reflective objects.

The CPL filter is one of the most important filters for landscape photographers when faced with water reflections and also to increase the contrast in the sky. 

3. Neutral Density Filter

The Neutral Density Filter (ND) is the main filter for long exposure photos. ND filters in physical form can be screwed or flat slot. ND stands for Neutral Density, said Neutral more or less because it does not change the direction nor the character of light. While the word Density due to its nature reduces the intensity of light. So more or less can be interpreted as a useful filter to reduce the intensity of light but not change the character.

The ND filter is also one of the most important filters for landscape photographers who like to take long exposures 

4. Graduated Filter ND

Graduated neutral density filter, commonly called graduated filter is a filter that has a function like ND filter but with a high intensity, the top is dark while the bottom is dark. This filter is usually used to photograph the landscape with subjects that have very wide tonal differences such as sunset or sunrise.


When we take pictures of sunrise or sunset on the beach, the difference between a clear sky and a much darker sea may be up to 3 stops or more (stop, what is that?). To equate both, we need to darken the sky while we let the sea part, so we put the filter graduated ND with 3 stop exposure different. The popularity of the Graduated ND filter drops slightly in line with the implementation of the increasingly "tacky" High Dynamic Range techniques.

5. Filter For Black & White Photos

There are some filters installed to block light with a certain wavelength for better black and white photos. There are filters Red, Orange, Yellow, Green and Blue commonly used by photographers of black and white photo enthusiasts.

For example, the Red 25 filter blocks red light and amplifies blue light, so the sky in black and white photographs can be more dramatic. This Black & White filter is rarely used in the age of digital photography.

6. Soft Focus Filter

Soft Focus filter is useful to make subject photo look softer, this filter will reduce the sharpness of the photo and make it look soft. This filter is usually used when photographing people's faces. By utilizing the diffusion of light created by this soft focus filter, we can create a rough facial skin to become softer and softer.
 Soft focus filters are somewhat rarely used considering the function can be made in photoshop and other retouch methods. 

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