All About Camera Filters

Using the Cokin Creative Filter System

aboutcamerafilters — Tue, 17 Aug 2010 10:25:21 +0000

Just about 10 to 15 years ago when digital photography was almost non-existent, every photographer had to depend on filters to create special effects or to correct the white balance. If not, they will need some nifty darkroom tricks. With screw on filters, you can still attach different filters but it is a less than elegant solution. For graduated filters, it would be almost impossible to adjust the filter up or down to fit your composition.

A Cokin Creative Filter System primarily consists of 3 elements. In the order that they are attached to the lens: adaptor ring, filter holder and lastly the filters themselves. Adaptor rings of different sizes allow the same filter holder to be attached to lens with different filter attachment size. In this way, you can potentially avoid buying the same filter of different sizes.

Illustration of the Cokin Creative System. Photo credit: Cokin

A good way to use the system is to combine a Gradual Grey (ND) series filter with other filters such as a polarizer or a UV filter. A graduated filter is a filter where the effect is at the maximum at one end and the effect gradually decrease until the glass is clear. A likely scenario to use this kind of filter is the sky in the background is too bright for the foreground. The photographer will then need to adjust the filter manually to the horizon or to the desired composition. Adding a polarizer can also remove unwanted reflections or improve the clarity of the sky. The effect is a well exposed photograph using such a combination of filters.

However such a system is not without its disadvantages. Firstly, you will not be able to use the original hood that comes with the lens. Cokin do sell a modular hood which you can attach to the front of the filter holder. Secondly, handling delicate pieces of filters and trying to take them in and out of the holder might be difficult in some situations.

Top 5 tips on buying and using camera filters

aboutcamerafilters — Sun, 15 Aug 2010 15:49:26 +0000

1. Always remember the worst piece of glass in the optical path will determine the image quality of your photo. If you are using a professional lens, you may want to use better filters so that the filters will not degrade your photos.

2. A good filter size to buy is 77mm. Good filters can be very expensive and you probably not want to buy the same type of filter of different sizes. Getting a larger filter and then using a step up ring is a good compromise. Sometimes it may also help to prevent vignetting on wide angle lenses. For example, some polarizers can be rather thick and will cause vignetting on wide angle shots. Alternatively, invest in a square or rectangular filter system such as Cokin Creative Filter System. A filter holder can hold a single or multiple pieces of filters in front of the lens allowing you to swap in or swap out filters to create the desired effect. For different sizes of lenses, just purchase different adaptor rings to attach to the filter holder.

3. If there is not enough light when shooting, remove your lens protector. Any filter will absorb some light.

4. Coating on filters reduces reflection and makes the glass much easier to clean. Fingerprints can easily be wiped off on coated filters. Even though they are more expensive than normal filters, they can prove their worth if you find it a hassle to clean filters.

5. Some filter manufacturers such B+W makes both brass and aluminum mounts for the same filter. Brass is more expensive but is supposed to prevent seizing of the rings. Sometimes filters can be very difficult to unscrew especially after being attached for a long time. Brass rings supposedly are easier to unscrew but some users of brass rings have also reported seizing of their filters. If you want the best money can buy, then go for brass rings. If not aluminum rings should satisfy most filter users.

Understanding and using a polarizing filter for photography

aboutcamerafilters — Fri, 13 Aug 2010 14:57:36 +0000

Question: What is “polarization”?
Answer: Polarization is used to describe the direction of the electric field generated by the propagation of electromagnetic waves. Polarization can be linear or circular. Linear polarization means the electric field generated by the wave is oriented in a single direction but in circular polarization, the electric field rotates as the waves propagate.

Question: Why use it in photography?
Answer: Sunlight that is reflected from non metallic surfaces is polarized. It would mean reflections from clouds, surface of the water, glass such as windscreen of cars and surfaces of vegetation are all polarized light. Using a polarizing filter, we can remove such reflections. However do remember that it will only work on reflections from non-metallic surfaces. Another point to note is the effect of using a polarizing filter cannot be replicated in photo editing software.

Question: What is a circular polarizing filter?
Answer: A circular polarizing filter actually consists of 2 optical elements but only 1 filter. The front element, which is facing the object being photographed, is a linear filter. This front element is what produces the effect of the polarizer making the sky darker and removes the reflections. The back element is a quarter-wave plate which has the effect of circularly polarizing the light coming out from the other side. Both linear and circular polarizing filters produce the same effect.

Question: Why do we have to use a circular polarizing filter for our modern day cameras?
Answer: For the reasons of correction operation of the auto focusing and light sensors, we have to use a circular polarizing filter. Linearly polarized light interferes with these sensors.

Question: What is the best way to use a polarizing filter?
Answer: There is no best way to use this filter. Since the effect changes when the front element is rotated, the photographer can choose the desired effect. For the most absorption of reflection, point your lens perpendicular (90 degrees) to the sun.

Different kinds of camera filters

aboutcamerafilters — Fri, 13 Aug 2010 14:17:42 +0000

Below is a list of popular filters but it is by no means exhaustive. Remember that filters can come in either square or round pieces of glass.

1. UV
Absorbs Ultraviolet rays. In sunny and outdoor photography, UV rays can sometimes makes the landscape hazy. Removing UV rays improve the clarity making the features more distinct. Photographers also like to use this filter as a permanent lens protector to protect the first piece of glass or the front element of the lens.

2. Neutral
This filter consists of an optical clear piece of glass that does not affect the colour balance. However, do remember that all type of filter will not allow 100% of the light to pass through. When using filters please take into account of your aperture and shutter speed.

3. Skylight 1B
As the name implies, this filter absorbs the excessive blue colour from skies to give the overall image a more balanced colour. Some photographers also use this filer as a permanent lens protector.

4. Polarizers
These filters only allow light which hits the glass at a certain angle and reflect the rest away. Main uses are to remove reflections and scatter light. More details are explained in the Polarising filter article.

5. Coloured filters
Such filters absorb light of certain colours. The aim is to restore the colour balance in unusual light situations. For example photos taken under fluorescent light have an unusual colour cast which can be absorb by using a FL filter. However due to the widespread use of digital photography where colour balance can easily be adjusted in photo editing software especially if photos are taken in the RAW format, very few photographers are still using these coloured filters.

6. Special effect filters
There exist filters to create special effects. For example a softener filter for portraits, or a sepia filter to recreate the effect of old photos. However with the rapid improvement on digital image enhancement, a lot of these special effects can easily be created in photo editing software.

What is a camera filter?

aboutcamerafilters — Fri, 13 Aug 2010 14:00:54 +0000

A camera or lens filter is a piece or multiple pieces of glass being attached to the front of the lens. In the case of lenses of Single Lens Reflex(SLR) cameras, the lens are threaded in front allowing filters of the same size to be screwed on. For some smaller consumer digital cameras, manufacturers may design special adaptors to allow filters to be attached securely to the camera. These filters tend to much smaller due to the small size of the lens on digital cameras.

The main purpose of using a filter is to change the light which enters the lens in a way desired by the photographer. The filter, being in the optical path, may block away certain colours or bend the light in a way to create special effects. A secondary purpose of using a filter for many photographers is to protect the front element of the lens, which is the first piece of glass or plastic in the lens. A filter offers protection against stains, fingerprints and dust. Good filters often have a special layer of coating which allows dust and prints to be easily wiped off. In addition, a filter adds a layer of protection against scratches or knocks. Since good lenses can be very expensive and in many cases more expensive than the camera itself, it makes economic sense to protect the lens as it is much cheaper to replace the filter rather than repair the lens.

However there are some disadvantages of using a filter. Firstly, the optical quality of a filter may not be as good as the lens since a filter is probably much cheaper. The filter may degrade the image quality of a photograph. Secondly, the filter not only blocks out unwanted light, it will also block off desired light to a certain degree. For example many polarizing filters take away 2 to 3 full stops of light. In many cases, the better the optical quality of the filter, the more amount of desired light it lets through. Thirdly, some filter systems prevents you from using the lens hood due to the size or shape of the attachment. An example is the Cokin Creative System whereby you attached a square filter holder in front of the lens. The attachment is usually much larger than the lens hood. Another example is when using a polarizing filter, you will need to rotate the filter and having a lens hood restricts access to the polarizing filter.