November 17, 2009
The accompanying images were all taken at the same camera settings. I used a Nikon D80 set on manual, a 18 – 135 Nikkor lens and a tripod. What is different from one to the next was filtration. The one with the lightest sky had NO FILTER. The next lightest had a 2 – stop, soft transition, gradient, and the darkest sky is the result of a 3 – stop, hard transition filter. These are both Singh Ray filters and are of professional quality, costing over $100 each. But, Cokin makes a neutral-density filter that is still quite useful for about one-fifth of that price.
Let me explain why the use of a neutral-density, gradient filter is necessary when you are shooting landscape images. A camera doesn’t see contrast with the same flexibility that your eyes do. When you look at the brightness above the horizon, your iris closes down, so that you see it normally. When you glance down at the darker areas below the horizon, your iris opens up, allowing more light to enter your eye and so you see at least 8 stops of contrast in a scene with ease. But, the camera can only encompass about 4 or 5 stops of contrast….often leaving you with a choice of either having ‘blown-out’ highlights—which is ugly and unacceptable—or ‘blocked-up’ shadows—which isn’t a lot better, but is the conventional choice. Therefore, the best choice is to be able to darken the brightest part of the frame, and not darken the less bright areas at the same time.
This is where the gradient filter comes in. It is a piece of rectangular optical quality acrylic that is dark on one end, with a smooth blend to clear on the other end. We have all seen sunglasses like this, but they aren’t usually completely clear on the bottom, just lighter. By mounting the proper n-d filter in a holder on the lens, one can look through the viewfinder and slide the filter up and down until they see the best position for it. When used properly, the result is undetectable to most viewers. In the example I have provided here, the 2-stop, soft, appears to be ideal. The 3-stop, hard is too much and too obvious, while the unfiltered scene appears kind of insipid. The overly dramatic use of orangey-brown gradients is done all the time…in television ads, mostly for cars. Somehow, they think it looks good. It just looks unnatural to me. The higher quality n-d grad filters are truly color neutral. The cheaper ones tend to have a slightly greenish cast...but that is easily addressed in Photoshop, so I wouldn't hesitate to use them.
So, take a look at these sample images. Almost all the landscape images I have made over the last thirty years have used an n-d grad filter. Once you get used to having that kind of control over the contrast of the scene, it is hard to surrender it. COMPUTER wizzes take note: it is also quite possible to gain this kind of control and have perfect results by skillful use of a gradient layer in Photoshop. My son, Sam, is so facile with PS, that he can make even the most contrast handicapped scenes look great. It is also important to remember that in digital photo-files, there is detail in the dark areas—even when they appear as ‘dropped’ shadows—that can be recovered by using various tools in PS, notably ‘curves’, ‘levels’, ‘shadow&highlights’ and even more advanced methods.
As long as you make sure there is data recorded in the lightest areas of the image—and most DSLR’s have a way of warning you if there is a blank area—the adjustments can be made in PS. No data, no adjustment.
Get out and play with your camera……the world is waiting.