Shooting with Filters
Those of us who shot film will remember schlepping (a technical term) bunches of filters in our camera bags. Some of us still do!
These are designed to perform several functions from saturating colors and cutting through glare to blocking light to altering the color of light.
Once digital photography came to dominate the market, the use of these little helpers declined sharply. With the many tools built into Photoshop and other processing software as well as the abundance of plug-ins and add-ons dedicated to providing filtering functions, many photographers these days carry few, if any filters.
It was a veritable rainbow of colored filters: blue, yellow, amber, pink, orange, red, magenta, green – you name it. For the most part, warming and cooling filters and others tinted with varying degrees of color density performed functions that today are easily replaced by the White Balance controls of Color and Tint. Dozens of pieces of glass and resin have largely been reduced to a couple of sliders and layers.
We also used such things as polarizing and gray neutral density filters, both split and solid. It is those relics that have survived the extinction of the rest of the dinosaurs and are still around today. Even with the magic of digital photography, these devices have proven themselves to be invaluable.
While a few pieces of software do offer the functions otherwise performed by these little beauties, digital technology has yet to come up with post-processing tools that can equal the performance of the real thing.
The various simulated polarizing functions available in today’s digital darkroom provide rotation and intensity settings, but unlike the real thing, cannot penetrate a reflection off the surfaces of water or glass. Whatever objects that may have been revealed on site are simply not in the image if no filter was used. This was the genius of Dr. Edwin Land, inventor or polarization.
The trick in using an actual polarizing filter is a simple one: don’t overdo the effect.
If a little is good, a lot is not always better. It is easy to be wowed when seeing the maximum degree of polarization through your viewfinder, but that will usually result in overkill when seen in the final image. I usually dial my rotating polarizer to that maximum and then back it off by about 50% for the best compromise.
That is a judgment call and is primarily affected by the angle of the lens to the light source. The maximum effect is achieved when the front surface of your lens is at a ninety degree right angle to the sun or other light source, while shooting with the light either directly in front or in back of you will produce virtually no polarizing effect.
Intermediate angles between these two extremes will produce commensurate effects.
If not actually viewing through the lens, hold the filter up to your eye, rotate the mount, select your degree of polarization visually, note the position of the filter ring relative to the top or bottom of the mount, attach the polarizer to your lens and then set the position that you have chosen on the filter mount. It sounds more complicated than it is. After doing it once or twice, it will become second nature.
If metering through the lens, make sure to use a rotating, rather than a linear polarizing filter. Otherwise, your exposure will likely be inaccurate.
Neutral Density Filters
Let’s talk about neutral density filters. Before we get into their operation, we need to make sure that they are really neutral. Some have a slight color cast, often a weak green, that can really mess things up later. Make sure to buy only top rated filters, both for color neutrality and optical quality.
These come in four basic varieties: solid gray with a fixed degree of density, solid with a mechanism that allows you to vary the density, graduated with a soft transition or graduated with a hard line splitting the gray and clear areas of the filter.
Let’s go through these in order.
The first is simply a solid gray filter that blocks light uniformly. That is its only function. This allows for a greater exposure to light, be it with a bigger aperture for shallower depth of field, a higher ISO (generally pointless) or by far the most widely used, a slower shutter speed. Using a slower speed will enable you to blur water or other motion. This is a great technique for waterfalls, wave action, flowers and other subjects blowing in the wind as well as panning with a moving subject when the light is otherwise too bright to allow for capturing the desired degree of motion. Since this type of filter comes in a variety of densities, you will need to select one or more to carry. My most often used is a 3 stop or 0.9. Many photographers opt for those that are significantly darker.
Option two is the same type of filter and function, but features a rotating mechanism that allows the user to choose the desired degree of density, sometimes up to as much as 10 full stops of light and therefore, the degree of motion captured. Great for multiple choices of motion.
Using any of the filters mentioned so far will require adding a compensation factor to your exposure in order to compensate for the light lost through the density of the filter. This varies with the particular filter, but will always be accounted for automatically with through the lens metering.
If metering with a separate light meter, try reading the scene straight on and then through the actual filter, subtract and adjust your exposure accordingly. Those discussed above all involve a uniform degree of compensation because they have a uniform density, variable neutral density notwithstanding, but still solid throughout the frame.
Exposure compensation with the neutral split filters is a bit more involved. We’ll discuss that in Part 2 later.
Jerry Ginsberg’s landscapes and travel images have graced the pages and covers of hundreds of books, magazines and travel catalogs. He is the only person to have photographed each and every one of America’s National Parks with medium format cameras. Jerry’s photographic archive spans virtually all of both North and South America.
More of Jerry’s images are on display at www.JerryGinsberg.com
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