Though it is true that there are many adjustments possible in Photoshop or even with the photo editor on a phone, it is still useful to employ filters on the camera to achieve your best results. The first filter I’ll mention is the basic UV filter or protection filter. A filter such as this is kept on the lens at all times with the purpose of keeping dirt off the lens itself. That way, if a scratch or dulling of the surface occurs, the lens is still perfect and the cost for replacement much lower. If you use expensive lenses, don’t cheap out on the filter. No point in a $2500.00 lens if it must try to function behind a piece of inferior glass. I show the Hoya HD2 UV filter (clear) because unlike many in that brand, this particular model is made of top quality glass and it is a thin design so it won’t get in the way functionally when using a wide angle or tilt shift lens. Price tag around $150.00. So much better than replacing a lens if the glass gets damaged. I banged a camera once on a hike but only broke the filter. Without it, I would have been out a very nice lens.
Other filters have a practical application. The circular polarizer, such as the Promaster one pictured here is a tinted filter with two pieces of glass the rotate to filter the light. They will add saturation to the sky, make clouds stand out much more vividly and in more detail, and deal with reflections on surfaces such as water. Such lenses will make color more rich and improve contrast, but at the price of blocking some of the light reaching the sensor. They are generally counterproductive in low light. They work best when the picture is being shot on a 90 degree angle to the direction of the sun. If the sun is directly behind or directly in front of the camera they won’t have much positive effect. The sky in the photo at right was possible thanks to the circular polarizing filter on the camera. Depending on size, these are typically up to $250 in higher quality models (B+W makes a nice set of filters). A quality camera shop such as Glazers in Seattle or B&H in New York will advise you well on particular brands and ones that may be on sale.
The first 2 filters should be in the bag or on the lens for every SLR camera. The final type of filter I’ll mention is more specialty but also quite useful. A neutral density filter can be used to block light without changing color. If you are shooting into the sun, it’s useful. You can get graduated neutral density filters that block light in only part of the image. Those can be adjusted to help get a sunset sky darker so it won’t blow out all detail if you take the exposure to see the ground level and not have it dark. A bright sunset and completely dark foreground is not generally a really pretty shot. Using neutral density, you can even out the exposure and see all parts of the photo. This is a graduated neutral density filter, meaning it is tinted on only part of the filter.
It is also possible to use neutral density so you can open the aperture even in bright or studio light. If you happen to have an f 1.2 85mm lens or f 1.2 50 mm lens, you can get really shallow depth of field effects, but the flash will overexpose the image when the aperture is that wide open. However, a neutral density filter can reduce the light entering the camera and allow you to make the most of that expensive lens. You can take an image with shallow depth of field and still use your studio lights so long as the filter is in place. This filter will be tinted equally on all parts of the filter, but some of them are variable and the amount of light blocked can be controlled by rotating 2 pieces of glass.
Taking a time exposure in daylight is also possible using neutral density. This allows for many special effects, such as the blurring of moving water seen here. This sort of picture is accomplished using a Lee Filter (another excellent brand), in particular, the Big Stopper that reduces light dramatically (10 F stops) and lets you take time exposures in daylight.
There are many other potentially useful filters…ones that impart sunset colors, special light effects and so forth, but many of these have been rendered less needed by Photoshop that can do the equivalent. If you have the filters mentioned in this article, you’ll have the most useful filters of all.