various filters in digital photography

Various Filters in Photography

UV Filter

• UV filters are used to block invisible ultraviolet light, to which most photographic sensors are slightly sensitive

• UV filters are primarily used to protect the front element of a camera lens from damage and dirt.

• UV filters reduce haze and improve contrast by minimizing the amount of UV light that reaches the sensors.

Polarising Filter

. Polarisers sort light into a single plane which helps to darken blue skies, increases colour saturation and reduces reflections in non-metallic objects.

. The effect created by a polarising filter is one of the only effects that can’t be replicated in post production so it’s important that you own one.

Areas where Polarising filters have the biggest impact

Water• It reduces the glare,water reflection and water colour

Sky The color of sky can change remarkably using a polarising filter. Rotating

the filter you’ll see a blue sky change from a light pale blue color to a vibrant and deep blue color

Colour

It cut down the reflection, this makes the colors of some of these objects more vibrant.

• There are 2 types of polarising filters Linear and Circular (CPL)• Linear are traditionally used in film photography• Circular is used in digital as they are designed to

not confuse the camera’s autofocus. When you attach the circular filter to the end of

your lens you will find that you can still rotate the filter, which changes the direction that the light is polarised

Infrared Filter

Infrared or “IR” spectrum is not visible to the human eye but in some circumstances it’s possible to capture it with your camera.

• Most digital cameras have an infrared blocker that is great for regular photography but obviously not for infrared work.

Ways to do an Infrared Photography1) Use a camera that includes a “night vision” mode. These cameras

generally include an infrared light

2) Modify your camera to natively shoot infrared

3)Use an Infrared Filter. Which is the easiest way.

ND Filters

Whats is ND filter

• A Neutral Density filter or ND filter is a filter that reduces or modifies the intensity of all wavelenghts or colors of light equally.

• They are called Neutral Density because the filter reduces all light wavelengths reaching your cameras sensor without affecting the colour reproduction

• It allows the photographer to select combinations of aperture, exposure time and sensor sensitivity which would otherwise produce overexposed pictures

• This is done to achieve effects such as a shallower depth of field or motion blur of a subject

Situations where ND filters are particularly useful include:

• Smoothing water movement in waterfalls, rivers, oceans, etc.• Achieving a shallower depth of field in very bright light• Reducing diffraction (which reduces sharpness) by enabling a

larger aperture• Making moving objects less apparent or not visible (such as

people or cars)• Introducing blur to convey motion with moving subjects

ND filters are quantified by their optical density or equivalently their f-stop reduction

Optical Density F stop Reduction ND No. Notation % Transmittence0.3 1 ND2 50%0.6 2 ND4 25%0.9 3 ND8 12.6%1.2 4 ND16 6.25%1.5 5 ND32 3.12%1.8 6 ND64 1.56%2.1 7 ND128 0.78%2.4 8 ND256 0.39%2.7 9 ND400 0.25%3.0 10 ND1000 0.1%

To explain by example , I have a 9stop ND filter. I set up the camera in manual mode and settings were ISO 100, f/9 and a shutter speed of 1/100s without

an ND filter and its showing a good exposure

Now when I placed the 9stop ND filter on the lens, cameras built in light meter was showing a 9 stop (9EV) underexposure for the same scene. So to ensure to ge the same exposure without the ND filter I needed to modify the lens aperture and the

shutter speed.

Use of ND filter for smoothing of water

f/9,1/80 sec, ISO 100 f/11, 50 sec, ISO100

Use of ND filter for motion blur

f/4, 1/1000 ISO 100 f/25, 10 sec, ISO 100

• One disadvantage of using an ND filter is that it darkens what you see through the viewfinder rather dramatically and depending on what type of filter you are using (16x, 32x etc) your camera may not be able to focus at all because it is so dark

Screw In System

• Hoya, B+W, Tiffen use Screw in filter systems

Filter Holder System

• Lee and Cokin use this system

Graduated ND Filter (GND)• GNDs have variable light transmission. Typically half of the

filter is of neutral density and the other half is clear.• It is used to bring an overly-bright part of a scene into

the dynamic range of sensor.

The GND filter comes in two categories:Hard edge & Soft edge

Variable neutral density filter• These work by placing two polarising filters together at least one of which

can rotate. The rear polarizing filter cuts out light in one plane• As the front element is rotated, it cuts out an increasing amount of the

remaining light• The advantages to this are that you get multiple ND filters in one package• The disadvantage is a loss of image quality caused by both using two

elements together

Some of my work with a 9 stop ND Filter

Thank You!