Essential Photography Filters Illustrated
Photography filters (the glass ones that you put on the end of the lens while you’re shooting; not the ones you add in Photoshop) have made a huge difference to the quality of my photos. That said, there is something of a steep learning curve associated with them, in terms of knowing which filters to use in which situations, and also in knowing how each filter will change the image captured. I have been wanting to post an article that visually illustrates the filters that I consider to be essential for a landscape photographer, but didn’t find a scene that really illustrated them well until just recently…
Shooting Without Filters
Let’s start with a couple of images taken WITHOUT any filters at all. The light a little while after sunrise is quite contrasty, and so without using any filters, I have to choose between exposing correctly for the lighthouse and the sky behind it (in which case the foreground is dark and under exposed), or for the rocks and water in the foreground (in which case the sky and lighthouse are bright and overexposed):
There are filters to overcome this dilemma!
Neutral Density Gradient (ND Grad) Filters
ND Grad filters are sheets of glass/plastic that slide into an adapter that you screw onto the front of your lens. One half of the filter is coated with a grey, neutral density coating that gradually fades into no coating at all. The light that passes through the grey area is darkened, allowing us to control the bright/highlight areas in the composition to make them more consistent with the dark/shadow areas. ND Grad filters come in a range of strengths… I have a set of three that achieve 1-stop, 2-stops and 3-stops of darkening, and the adapter is such that I can stack them on top of each other to achieve up to 6-stops of darkening in one half of the image.
Although I have achieved correct exposure throughout the image with thanks to the ND Grad filters, the reflection of the lighthouse is “shimmering” a little too much for my liking…
Black Glass Filter
I have a Hoya NDX400 filter (often referred to by photographers as “black glass”) that screws on to the front of the lens to darken down the whole image by a whopping 9 stops! In mathematical terms, the NDX400 filter allows only 1/500th of the available light to enter the lens. Or put simply, I have to double the normal exposure time 9 times to get a correct exposure when the NDX400 filter is on. As such, a common use for the NDX400 filter is to achieve long exposures in daylight conditions. I typically use the NDX400 to smooth the surface of water, as is my style, and the effect that I need to reduce the shimmer in the reflection of the lighthouse here.
You may also notice that application of the NDX400 filter has resulted in richer, deeper colours here… a nice side-effect of the long exposure achieved through this filter.
While I do think this is a pretty decent image so far, there is one more thing that could make it just that little bit better. We can see that there is some interesting textures below the surface of the water in the bottom right corner of the image… imagine how much better the image could look if we could see some more of that underwater detail!
Circular Polarizing Filter
A Circular Polarizing filter (or CPL) allows us to control the reflections of light that are allowed to enter into the lens when we shoot. Without getting too scientific about it, light emitted from a light source (except for a laser) is omni-directional… it goes every which way; whereas the light we see reflected off a surface only travels along a single plane. The CPL filter allows us to block out the light reflected along any given plane, thereby minimizing the reflections that we see in that plane. The ability to do this has many applications, such as returning contrast and saturation to an overly reflective scene… or in the case of this example, cutting down the reflections on the surface of the water so that we can see what lies beneath:
The Finished Image
With a little post-production work in Lightroom and Photoshop, the finished image can be seen below (click to view larger)…