Filters

Botanical Gardens, Dublin - Circular polariser used to boost blue in sky and 

banish reflections in glass.

Carlingford Lough, Ireland - Circular polariser used to boost blue and reduce the 

glare from sun.

Botanical Gardens, Dublin - ND4 filter used to lower shutter speed and blur water.

Filters those small pieces of coloured glass or resin we stick on front of the 

camera lens to give us weird and wonderful visual effects.

Note : Do not use a polarizing filter if you are taking multiple 

          photos to combine later to make a panoramic image as the

          polarizing effect will change as the camera pans around the

          scene in an arc.

Note : Use a polarizing filter to reduce glare when taking dusk and

           dawn coastal photographs.

Note : In winter blue skies tend to be a darker blue then any other 

           time of year, if you use a polarizing filter on a winter blue sky 

           it will appear a very dark blue in colour.

1. UV 390 - Universal filter that absorbs uv radiation of up to 

                   390mm to eliminate haze.

2. Skylight 1A or 1B - For colour photographs, eliminates blue 

                                   cast for warmer tones.

3. Correction Filters - Diminishes the colour temperature of the 

                                   light, red, blue, black and white.

4. Neutral Density - To reduce the amount of light reaching the

                                film or sensor and reduce depth of field 2x, 

                                4x, 8x levels available allowing you   

                                to slow movement useful for 

                                photographing water, light trails and creating 

                                ghostly figures. For example  you want to 

                                photograph using a shallow DOF but you are 

                                unable to go lower than f/5.6 without the 

                                image being overexposed you can use an ND

                                filter to reduce the light coming into the 

                                camera and allowing you to set the lower 

                                aperture of f/2.8 and so reducing your depth  

                                of field, great for  photographing flowers or 

                                portraits. 

5. Polarizing Filters - Linear - Clarifies colours and richness by 

                                               suppressing non metallic reflections

                                               i.e glass, water, surface and glare 

                                               on a sunny day, used manual 

                                               focus cameras, normally a polarizing

                                               filter has a 2 stop exposure 

                                               reduction making it handy reducing

                                               shutter speeds.

6. Polarizing Filter - Circular - same as linear except light travel 

                                               through circular plane, used on AE 

                                               and AF cameras.

7. Underwater Filters UW - To Eliminate Blue or Green cast of 

                                            water.

8. Split Field Bifo - Close up lens covers half of the filters to bring 

                              both close and distant objects into focus.

9. Special Effects Filters - Fog filter diffusion, filter diffraction, filter 

                                         diffuse and spot diffuse, sand spot  

                                         barrel filter, streak filter, whirl pool 

                                         margin dynamic spot whirl pool center, 

                                         basket filter and radial filter.

10. Colouring Enhancing Filters - Red, Blue, Green, Sepia.

Filter comparisons

Light Reduction          Cokin Filters       Lee Filters

1 stop                             ND 2                    0.3 ND

2 stop                             ND 4                    0.6 ND

3 stop                             ND 8                    0.9 ND

4 stop                             ND 16                  1.2 ND

5 stop                             ND 32                  1.5 ND

6 stop                             ND 64                  1.8 ND

7 stop                             ND 128                2.1 ND

8 stop                             ND 256                2.4 ND

9 stop                             ND 512                2.7 ND

10 stop                           ND 1024              3.0 ND

Note: Not all ND or ND graduated filters are colour neutral

         they all cause some sort of colour cast to be applied

         to your captured image. Capture an image of your scene

         without any filters set in front of your lens to use as a 

         colour reference that can be used to compare both images

         later in photoshop when the colour cast has been removed.

Note: In Photography_101 > Photoshop, I have included some 

         ways to eliminate colour casts in your captured images.