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Filters

Although color balance capability in digital cameras have reduced the need for filters, they do still have limited application. The filters having particular interest to digital photographers are UV/Protection filters, Circular Polarizers, ND filters, Graduated ND filters (sometimes called Grads or Color ND filters), and perhaps Star filters. When selecting a filter, buy a good brand, as it makes no sense to buy an expensive lens and put on a cheap filter. Cheap filters have issues, and they might alter your image quality. Filters from B+W, Hoya, or Tiffen are acceptable.

If you are shooting underwater photos on that Caribbean vacation with a camera housing, you will want to look at a Red color balance filter. When you go underwater, the light is selectively filtered with a shift towards Blue. A Red filter helps correct it. As an alternative, some underwater cameras have an underwater color setting, and some cameras can be set with a custom setting with bias towards the Red spectrum.


 

UV/Haze/Protection filters.

Many photographers use UV/Haze/Protection filters to protect the lens of their camera, as the idea is that any damage that occurs will occur to the filter and not the lens. Although they are called haze filters, they in fact do nothing to reduce haze. This is unfortunate, as many times on cruises such as in the Caribbean, the hot - humid weather can cause significant haze - especially over water. A haze filter is no help in this regard. The only options are to avoid long telephoto photographs over water, and/or attempting to fix it in post processing. Post processing improves, but does not eliminate haze.


I took this photo from a cruise ship as we were entering the harbor in Cartagena, Columbia. It was early April, but the haze was already a significant challenge.
 
 

A quick look at the histogram in the post-processing software reveals a limited dynamic range, which was caused by the haze. Some correction can be done with this photo.
 

This is the photo after the dynamic range was corrected. Still far from perfect, but a significant improvement. There is just not much that can be done with this photo.
 
 

The histogram shows that I eliminated the voids at the dark and bright extremes of the photo - that is all that I did. A little more processing might improve things a bit more.
 


 

Polarizing Filters

Polarizing filters may be among the most useful filters for digital photographers. There are two types of polarizing filters available, Linear and Circular. Due to how the digital systems work, Linear Polarizers will not work with digital cameras - you have to use Circular Polarizers.

Polarizers generally have two purposes; they cut down on the sun's glare, especially through windows and water. They are also useful to darken the sky. Be aware though that most polarizers reduce the available light to your camera by -2 EV. As polarizers filter out polarized light, the filter can be rotated on the lens. The idea is to rotate the filter until the polarizer is perpendicular to the polarized light, thereby blocking it. If you are on a tour bus on an excursion, and have to shoot your photo through the bus window, a polarizer can make all the difference.

 


This photo was taken with a polarizing filter set to minimum (no effect). Notice the significant glare from the sun on the windshield.
 
 

This photo was taken with a polarizer, rotated to minimize the glare. Some glare exists, mostly due to the curved nature of the windshield all but scatters the light into different angles. But it is much improved, and you can often completely remove glare on a flat glass surface with a polarizer.
 

This photo was taken with a polarizer, rotated so that it would have no effect. Notice there is a lot of glare from the water.
 
 

This photo was taken with the polarizer set to reduce the glare of the water. Notice how it completely changes the exposure as well.
 

This photo was taken with the polarizer set to minimum, which still results in a -2 EV light loss. Nice enough photo.
 
 

Similar photo, taken under the same conditions, but this time, the polarizer was rotated until it darkened the sky.
 


 

Neutral Density Filters

 

The sole purpose of Neutral Density (ND) filters is to reduce the light level. This might not seem apparent at first, but it allows you to slow the camera down to use shutter speeds or apertures that are normally beyond the camera's range. Neutral Density filters are available in a wide range of intensities, from - EV to -13 EV.

If you can only buy one ND filter, which filter would it be? While many recommend a ND4, I would recommend a ND16. The reason being that by using a ND16, you can easily make up the 2 EV difference when setting exposure in your camera. The ND4 on the other hand, may not go far enough.

Neutral Density Filters
ND2
ND 0.3
1/2 (50%)
1 EV
ND4
ND 0.6
1/4 (25%)
2 EV
ND8
ND 0.9
1/8 (12.5%)
3 EV
ND16
ND 1.2
1/16 (6.25%)
4 EV
ND32
ND 1.5
1/32 (3.12%)
5 EV
ND64
ND 1.8
1/64 (1.5%)
6 EV
ND128
ND 2.1
1/128 (0.8%)
7 EV
ND256
ND 2.4
1/256 (0.4%)
8 EV
ND400
ND 2.6
1/401 (0.25%)
8.65 EV
ND512
ND 2.7
1/512 (0.2%)
9 EV
ND1024
ND 3.0
1/1024 (0.1%)
10 EV
ND2048
ND 3.3
1/2048 (0.05%)
11 EV
ND4096
ND 3.6
1/4096 (0.025%)
12 EV
ND8192
ND 3.9
1/8192 (0.012%)
13 EV

 


This photo was exposed for 100 seconds, using a ND400 filter (8 EV reduction). While fireworks photos are normally taken at 20s to 30s exposure times, extending the exposure allows multiple fireworks to fill the screen. There are at least 25 bursts in this photo.
 
 

This photo was taken for 1 second in the late afternoon. A ND16 filter was used to allow a correct exposure to be taken in daylight conditions.
 


 

Other Filters

Other popular filters include Graduated ND filters (sometimes called Color ND filters) and Star filters. A Graduated ND filter has neutral glass on the bottom half of the filter, and a Neutral Density area on the upper half. These are available in various EV densities, and are used to darken areas such as the sky in landscapes. Star filters are available in 4, 6, 8, or more points, and are used for special effects of light sources.

 


This photo was taken with a Graduated ND filter having a -2 EV rating. It looks very similar to the photo above that used a minimized polarizer. However, just the top portion of this photo is darkened. Compare the grassy area with the polarized photo, and you will see that the grass is brighter with the Graduated ND filter.
 
 

This photo was taken with a 6 star filter on board Royal Caribbean's Monarch of the Seas. It makes for a fairly nice effect.
 

 


Non Filters

You don't always need a Star filter to achieve the Star effect. Some lenses that have superior aperture diaphragms naturally produce a star effect, and some cameras have in-camera processing that can produce stars.


This photo was taken with a Nikon 80-200mm f/2.8 having a 9 blade diaphragm. This results in an incredible 18 point star. No filter was used with this lens; it just naturally produes them. Lenses with rounded diaphragm blades suppress stars, so your results depends your lens.
 
 

This was a macro photo taken with a Nikon D90. The camera has a star function that created this effect. No filter was used. The nice thing about doing this in-camera is that the original is not changed. A copy is made before the camera produces the star.
 

 


Wide Angle Lenses

There are two cautions with using filters on wide and super-wide angle lenses. First, do not use a polarizer on these lenses, the lenses are so wide that the filter effect will not be uniform across the entire lens. One segment of the photo will be polarized and another will not. Secondly, some filters are designated "wide angle" as they have a thinner ring to prevent vignetting as the angle of view is so wide. Obvously, stacking filters on wide angle lenses is also to be avoided.

 


Attaching the filter.

Virtually all DSLR and interchangeable lens cameras can use filters. You will typically find the filter size listed on the front face or bottom of the lens. It will have a symbol such as "Ø58mm", which would mean this camera lens accepts 58mm filters.

Unfortunately, most compact cameras cannot use filters. There are a few exceptions, such as the Nikon AW100 and Nikon AW110 as they include a 40.5mm filter attachment in the box. This is ideal as you usually want a Red filter on an underwater camera to compensate for the color shift.

The photo at the right shows the Nikon AW100 with a filter attached.

A few other compact cameras, such as the Nikon P7700 and Canon G15 have lens and filter adapter barrels that can accept 58mm filters.

Finally, there is one other option that can be used for some compact cameas, especially the smaller models.

The Zekios filter adapter for compact cameras shown to the right can be adapted to many compact cameras. However, with a 37mm filter thread, filter selection is limited as there are not many filters this size.

The adapter base screws into the tripod mount of the camera, and I have found that this adapter works best with cameras having a tripod mount near the center of the lens.

Some compact cameras have tripod mounts off center, near to one edge of the camera. This adapter may not work with those cameras.

What size filter to buy: If you have many lenses, chances are that they will use different filter sizes. This is unfortunate as it can cost a fortune to buy the same filter in different sizes. One solution is to buy the largest filter your lenses use, then buy inexpensive step-down rings to attach them to your other lenses.

Most professional lenses use 77mm filters, and should you go with one of those filters, you can buy adapter rings for 72mm, 67mm, 52mm, or any other lens filter size you need. One word of caution though. If your lens requires a larger filter than you have, avoid buying a step-up ring (although they are available). A step up ring can cause vignetting on the lens that needs a larger diameter filter.


Resources

 
Source for products mentioned in the article.