Photography News Issue 37

Photography News | Issue 37 | absolutephoto.com

Technique

Graduatedneutral density filters

With ND grad (1/50sec at f/16, ISO 100)

©KingsleySingleton

GearGuide: Cokin Creative Gradual ND Kit £49.99

To control dynamic range, try using the Cokin Creative filter system’s Gradual ND kit, which comes with three different strengths of softly graduated filter, ND2, ND4 and ND8, corresponding to 1, 2, and 3-stop reductions in light at their maximum strength. The set is available inMedium (P-series) now, with Large (Z-Pro) and Extra Large (X-Pro) sizes coming soon. A corresponding holder is needed to slide the filters into, and this can be bought as part of the kit for a small increase. point the camera at the sky and read the shutter speed off again. If it’s 1/40sec you’ll need a one- stop grad (ND2 or 0.3); if it’s 1/80sec you’ll need a two-stop grad (ND4 or 0.6). Placed correctly, this will equalise the light, but in reality, it’s just a guide fromwhich you can decidewhether you want amore subtle or stronger effect. Placed correctly? Well, that’s down to where youposition the start of the grad effect. AnGND will be longer than a full ND filter allowing you to move it up or down in the holder and align it with your composition. For this reason, although you can get screw-in GNDs that rotate on a bezel, they are far less flexible than slot-in filters. So, where should it be placed? That depends on the look you want, but the most natural results are found when aligning the start of the gradwith, or just below, the horizon. Place the it too high and you’ll get a bright strip of sky above the landscape; too low and the horizon will be unnaturally dark. The effect can be difficult to judge through the viewfinder, so try a test shot, use the depth-of-field preview button or live- view. Of course you can angle the grad, too, if it suits the scene, or fits the light better; just experiment until you get the look youwant. Anything else? Certainly. The rate of transition (soft, neutral or hard) that you use is also a factor and can depend on the subject you’re shooting, how it’s framed and the aperture settings employed (the latter can also make the effect more or less obvious). For instance, a straight horizon is a better fit with a hard grad, while a soft transition is more appropriate on a more broken skyline where buildings or trees extend into the sky. However, when shooting seascapes, soft grads can do a better job, due the amount of reflected light. The wider you shoot, the quicker the transition can be from dark to light in the scene, so hard grads can be better there, too. Remember, you can also stack grads with other grads, or with full NDs to increase the effect or slow the shutter at the same time.

What they are: Like full Neutral Density filters, GraduatedNeutral Density (GND) filters (also called grey grads, graduate and gradual NDs), are designed to hold back a measured proportion of light; unlike them, this is only done in a portion of the frame. The effect of a GND gets stronger from one edge to the other, so, while one part of the filter is stopping some of the light, another is stopping less light, and one part is stopping no light at all, it being just a plain piece of glass or resin. GNDs vary in strength and are rated in the same way as full NDs (ND4, 0.6x, etc.) and also in their rate of transition from the full density of the filter to the clear part (defined as soft, medium or hard), so you can tailor them to the scene you’re shooting. When to use them: While full NDs are designed to stop light in a uniform way, being equal in strength across the frame, the varied effect of a GND filter only lessens light intensity in the portion of the frame where youwant it to; therefore they’re ideal for controlling the light across a wide dynamic range. That means, if the scene you’re shooting includes a sky that’s much brighter than the landscape (which is common) a GND can hold back some of the light in the brighter areas, balancing and improving results. This is increasingly important at wider angles of view, as inmost landscapes, because the broader field of view is likely to contain more variation in

With ND grad (1/50sec at f/16, ISO 100)

©KingsleySingleton

light than a cropped one. Lost detail and colour can be returned to overexposed skies, which almost always improves the look. How to use them: The first question is what strength of GND is required, and this can be judged by the difference in brightness between the landscape and the sky. So, in aperture- prioritymode,pointthecameraatthelandscape, and the camera will give you a shutter speed for a good exposure of it. Let’s say it’s 1/20sec. Now

Above When skies are too bright they lose detail, so a grad filter is required to darken that part and leave the rest unaffected. Below Positioning the grad is important; place it too highly and you won’t cover enough of the sky; too low and the landscape will look unnaturally dark. It’s often easier to assess this using live-view, rather than through the viewfinder.

Correct position

Postion too high

Position too low