Filters

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6/8/2007 7:26:08 PM

When it comes to filters, photographers can go crazy filling their gadget bag with loads of filters. This made sense back in the film days particularly for those who make their living shooting black & white. The problem was correct rendering of colored objects in the monochromatic film medium. Blue sky recorded as light gray, white puffy clouds were rendered the same. This made the landscapes flat. Yellow filter came to our rescue. A yellow holds back blue thus rendering the sky darker, now the clouds were visible. Red filter gave even more dynamic sky renderings. Green filter lightens vegetation. Often when doing table-top shots of cereal boxes etc. the various colors failed to show proper separation, reds and blues photographed as the same shade of gray as one example. We used filters to enhance and separate. When we shot color, we needed a battery of filters to color correct as a countermeasure for the various types of light sources. Otherwise our shots were often too warm or too cold. Digital with white balance and editing software with hue and saturation adjustment, changed all that. While some will disagree, I think the need for filters in digital work is minimal.

Now the question becomes, what filters are needed for digital work? The one that should be in your gadget bag is the polarizing screen commonly called a polarization filter. This filter is a neutral gray glass that stops about 4x of the light meaning you must open up two f/stops when this filter is mounted. Don't worry, your camera will automaticaly do this. The filter mount allows the filter to be rotated as its orientation must be adjusted for effect based on the direction of the illumination. Best when used on an SLR design as you need to see for yourself the different effects. You need to observe as you compose and rotate. The filter serves to subdue reflections from some objects (non-conductive surfaces). This filter provides some haze penetration thus is a must for landscape work. The filter darkens sky and generally increases saturation without applying a color bias. A must have filter for shots of glass or other shinny painted surfaces etc. Allow some surface penetration so you can see the fishes swimming in the shallows. The filter comes in two types, circular and linear. The linear is less expensive and works best but this design will sometimes thwart auto focus and exposure metering systems as they often depend on built-in polarizer’s. The circular type can safely be mounted as it won’t interfere with these sensor mechanisms.

The next most valuable is a graduated filter. A must for many landscape photographers as it evens out exposure the differences naturally occurring between background and foreground, particularly helpful on bright sunlit vistas.

The next most valuable gadget is a good lens shade. Serves to shield your lens from side light entering the optical path during the exposure. This scatter light causes flare which is devastating as it flattens and otherwise demolishes contrast and can create optical ghosts and glare spots.

The most overblown filter sold is the skylight. A UV filter used to cut haze encountered mainly in high altitude work. Has little effect on haze at low altitudes. Often tinted warm so it reduces the bluish cast of shadows in a sunlit vista that otherwise will be blue as they are illuminated by scattered light from the blue sky. Sold as a protective cover for your wonderful lens, best serves the purpose of lining the pockets of the camera sales force.

Alan Marcus
Ammarcus@earthlink.net

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6/8/2007 9:05:38 PM

A polarizer is important to have for all the reasons Alan mentioned. When using a polarizer, be careful that you do not end up with an overly darker corner of the sky in the shot, It will look unnatural.

When shopping for a Grad. ND Filter. Be sue to get a rectangular one that fits in a holder in front of the lens. That way you have the flexibility to adjust the transition up,down and even on an angle. The screw on types put the transition across the center of the lens which is rarely where you would want it. Also be sure to get a true Grad ND and not a Gray grad. Some excellent brands are Shing-Ray, Lee and Hi Tech.

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6/8/2007 10:01:51 PM

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6/9/2007 3:52:52 AM

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6/9/2007 6:18:48 AM