Using Polarisers, ND’s and ND grads
Written 8 years ago by Mark Evans
Polarisers, Neutral density, and Graduated Neutral Density filters can be an extremely useful addition to any photographers kit, but unless you know what you’re doing, and know when and where to use them, you may end up with more duff shots than you thought.
Polarisers are in their element on sunny days, reducing reflections, and deepening colours. It is however important to note that polarisers work best when used at 90 degrees to the sun; at less than 90 degrees the effect is not as pronounced. And while it may seem like a good idea to use one all the time, there are situations where it may not be so wise to do so. For instance; polarisers deepen shadows, so if your scene contains a lot of shadows, then you may lose some shadow detail. And on wide angle lenses, you may find that polarisers don’t tend to work so well, this will show in the sky; it will fade from dark to light across your image. Another thing to note is that polarisers usually reduce the amount of light coming into your lens by 1 or 1.5 stops, so if your camera has Through The Lens (TTL) metering then you wont have to worry, but if you don’t then you’ll have to compensate for this.
Having taken all these things into account, you’ll be raring to to get some snaps with your polariser, and operation is very straight forward with SLR type cameras; with a polariser that has the appropriate thread, you screw it on the front of your lens, look through your eye piece, and rotate the polariser until you get the desired effect, before taking your picture. You can also get film holder type polarisers, which slot into the holder and operate in the same manner. -If you’re buying a screw-in type filter then make sure you take a note of the thread size on your lens before you go out and buy one.
Polarisers and Rangefinders
Unlike SLRs, the eye piece view on a Rangefinder camera is not taken from the lens, hence, when you use a polariser on such a camera, you wont see any effect at all until you look at the taken picture. However, you can still use a polariser; its just a bit harder. Enter the Heliopan Polariser; this nifty piece of kit has numbers marked around the outside of the filter, so is perfect for use with rangefinders. Basically you hold the filter up to your eye, and while facing in the same direction as your camera will be, rotate the filter until you get your desired effect, take a note of the uppermost number on the filter, screw it on your lens, rotate it till your previously noted number is at the top again, then take your picture. Admittedly, this is a bit of a convoluted process, and is probably best suited to landscape photographers than anyone else, but I’ve found this method to be pretty effective when using my Xpan. You can also get a Kenko polariser, which consists of two calibrated polarisers with numbers on; a small viewing polariser mounted in the hot shoe, and the other on the lens. With this one you rotate the viewing polariser to get the effect you want then match the number on that with the one on the lens, a bit simpler and quicker if you’re taking spontaneous shots. I bought my Heliopan Polariser from Teamfoto. Kenko polarisers can be bought from Robert White.
Neutral Density Filters
Neutral Density filters are handy when you need to extend your exposure time without having to decrease aperture or ISO. There are many situations where this could be beneficial, such as blurring waterfalls, streams, waves and many others. And fortunately, they are pretty straight forward to use. Just screw-on or slide in the filter that will give you the shutter speed you want and take your picture, although you may need to experiment with different strength ND’s to get what shutter speed you want, so its handy to have a selection (1 stop, 2 stop & 3 stop), but if the budget wont allow, then I usually find the 2 stop the most useful. If you find you need more than a 3 stop filter then you can always stack them, (eg. for a 4 stop use a 1 stop and 3 stop together) or you can buy darker filters individually.
Graduated Neutral Density filters are the Landscape Photographers best friend. Great for balancing exposure of the sky with the land, these bits of glass or plastic are indispensable, although when you’re first starting to use them, they can be a little tricky. First of all you’ll probably need a set of ND grads, I have a set of Hitec ND grads with soft graduations, which come in 0.3, 0.6 and 0.9 strengths, but you can also get hard graduations which basically graduate from clear to dark over a smaller area. Now when it comes to using them, you need to know what the difference in brightness between the sky and the foreground is, so that you can select the correct one to use and hence balance the exposure of the sky with the foreground. So for a 1 stop difference, you would use the 0.3 and for a 2 stop difference, use the 0.6, etc. To get the difference, you need to get the exposure for the sky, so point your camera at the sky (without the filter mounted). Lets say your camera is on Aperture Priority mode, set to f/16 and it gives you a shutter speed of 1/250s. You then point your camera at the foreground of your scene, and it gives you a shutter speed of 1/60s. From these settings, you can now see that the difference is 2 stops (1 stop from 1/250 to 1/125 and 1 stop from 1/125 to 1/60)and therefore you should use the 0.6 filter. All that is left is to compose the shot, align the filter so the graduation is in line with the horizon (dark part over the sky!) and take your picture. In tricky situations the use of a hand held light meter, such a Sekonic, might be needed but with a bit of experience you may even be able to guestimate which filter to use in most situations.
Using Graduated Neutral Density filters with Rangefinders
If you have a rangefinder, then you’ll already know that when you put a filter over the lens, you won’t know what the effect is until you look at the picture. So using ND grads on a rangefinder can be a bit of a problem. I have an Xpan, so firstly I work out what filter I need as described above, and then for the filter position, the best way I have found is to look through the viewfinder and check the position of the sky in relation to the foreground; lets say the sky covers a third of my scene, then I’ll look at the front of the lens and position my ND grad so that the top third of my lens glass is covered by the dark part of the filter. Sometimes its a bit hit and miss, but most times this method works really well, and as always, with a little practice, you’ll have bagged some nice shots.