– Set the camera to let in the least amount of light possible. Choose the lowest ISO at your disposal (whether that’s 100, 50 or something even lower) and stop down your lens to its minimum aperture—which is hopefully somewhere in the neighborhood of f/32. (If you know you’re likely to want to make long exposures, start by choosing equipment that helps—like lenses with small minimum apertures. Or you could become a large format film shooter and get even smaller apertures like f/45 and f/64 at your disposal, and even lower ISOs through pull processing. Since chances are good you’re not going to start shooting large format film, we’ll keep discussing digital camera options.) The downside of a tiny aperture is that you’re likely to get a bit of distortion, and your image’s maximum sharpness will suffer compared to the sharpest apertures in the middle of the range. But unless the light is low, you’ve got to make some compromises. This is one.
– Find lower light. I know, this one’s sort of cheating since you likely can’t move your waterfall (or any other landscape element) from daylight into shadow, but you can choose to go out hunting for long exposure subjects on cloudy days or in wooded areas where the light will necessarily be lower. If a basic daylight exposure at ISO 50 is 1/15th at f/32, in shade that might drop by two stops down to a quarter of a second. Add some overcast haze to the sky and maybe it’s down to a second. Now we’re getting somewhere.
– Filter your lens. On my afternoon expedition I didn’t have the ideal long exposure filter—neutral density—but I did have a filter that would cut two stops of light and get me to a long exposure in the neighborhood of five or six seconds. It was a two-stop polarizer, and it was just the thing to get my shot from a fairly static waterfall into a nicely blurred image. A well-prepared landscape photographer would surely have a neutral density filter, which is just like it sounds: neutral, in that it doesn’t change the color or contrast of a scene, and dense—like sunglasses—to cut the amount of light passing through. ND filters, as they’re known, are available in everything from a half stop to a whopping eight stops of light cutting power. For making long exposures, anything two stops or more is going to be imminently helpful. If you’re locked down on a tripod and a longer exposure won’t do anything but make for a more artful image, don’t hesitate to go for a really dense neutral density filter. A few stops more would have definitely increased my options, both in terms of shutter speed and aperture for depth of field in order to affect the amount of blur, as well as depth of field and sharpness issues.
– Calibrate your monitor. There’s the discount approach to monitor calibration, which is usually built into the software straight from the factory, but for real monitor calibration accuracy you’ll want to purchase a third party hardware/software combo that can not only read the exposures produced by your display, but then use that information to create a custom monitor profile. Profilers from X-Rite and Dataexposure can be had for under $200, and in my opinion they’re worth their weight in gold. Here’s how highly I think of monitor calibration tools: if you’re currently working in an un-calibrated system, there’s no better investment you can make to improving the quality of your photography than purchasing a monitor calibrator. Given their relative low cost, it’s an investment you shouldn’t hesitate to make.
It should go without saying that for daytime long exposures we want to take the same basics steps for sharpness that you would for a low-light long exposure—namely, putting the camera on a tripod and using a cable release and/or mirror lockup to minimize camera shake. After all, a long exposure is a long exposure, whether it’s made during the daytime or at night. They’re just a little bit trickier during the day—unless you’re prepared with the right equipment and know-how.