Give your daytime shots a twist with a long exposure.
Using a longer exposure means that moving objects such as clouds and water can take on a magical feel.
I will agree the thought may seem absurd. Why would you ever want to use a longer exposure during the day given the abundance of ambient light perfect for using those high shutter speeds and a less chance of motion blur? Well, it's for ... want of a better expression, 'an artistic choice'. When you look at an image taken during the daytime some of the things you'll first notice is how sharp it is, free from camera shake, and how much everything is frozen in place.
Now if that's the look you're going for then that's fine, but lets consider how the world changes when you try taking an image at night. Have you ever noticed how much things are a bit more surreal at night when your shutter speed drops to seconds or even minutes to make an exposure. Those longer exposure times mean that moving objects such as clouds, water, people or cars taken on a magical feel. Including some of that feel to your daytime shot can not only be fun but can elevate your image from a standard capture to something wildly creative and engaging to the viewer.
So how do you take control of the daylight to achieve the shutter speeds required for this effect? Well, you'll need a few pieces of kit. It goes without saying that first you'll need your camera and your favorite lens. For this kind of work as a Canon shooter I use a Canon EF-S 10-22mm F3.5-4.5 USM or a Canon EF 17-40mm f/4.0L USM. However if you've got a full frame camera then a Canon EF 16-35mm F4L IS USM / Canon EF 24-70mm F4L IS USM is also a great setup.
Because you're dealing with deliberately long exposures there is no question you're going to need a tripod to keep your camera perfectly still. The shutter speeds you may encounter will require that you use a remote shutter release or setting your camera to a 2 second timer mode to avoid any camera movement. Last and certainly not least is a neutral density filter. Without this bit of kit, the long exposures you require just can't happen.
A neutral density filter is simply put, sunglasses for your camera lens. It filters out a certain amount of light that passes through your lens to your camera sensor. Much like the glass you'll see in a welder's mask which I will say some photographers have actually used as an ND filter.
The Canon EF 24-70mm F4L IS USM is a great lens for most shooting conditions. However If you find you need a wider field of view then something in the Canon EF 16-35mm F4L IS USM or APS-C Canon EF-S 10-22mm F3.5-4.5 USM shown below is what you'll need.
Manufactures like Lee, Cokin and Formatt Hitech offer a wide range of rectangular filters and filter holders.
Screw in filters can be cheaper however by going that route you'll be restricted to buying ones that will fit the diameter of each lens you're using.
A sturdy tripod is essential for long exposure photography to avoid any possibility of camera shake.
A good cable release or one of the more advanced intravalometers often used for creating time lapses is also a useful tool to control your camera remotely when shooting longer exposures.
There are many types of ND filters. There are the versions that are flat rectangular pieces of plastic/glass that slide into place within a holder that screw to the front of your lens via an adapter ring. Then there are the circular screw-on types of various sizes for different lenses.
Essentially, they also come in a range of optical densities. A standard ND2 (1-stop) filter will only let in 50 percent of available light, whereas a ND4 (2-stop) filter will only let in 25 percent, an ND8 (3-stop) lets in 12.5 percent, while a ND16 (4-stop) filter blocks out 25percent and so on. For long exposures during the daylight you'll typically need a ND1024 filter otherwise known as a 10-stop filter which allows 0.098 percent of available light to enter the lens and reach the sensor.
As you would have guessed cost for these filters vary too. A 10-stop filter by Lee, for example is in the range of $129 but you will also need to purchase the filter holder kit as well for about $100. A single screw-in type filter, depending in the lens size that it has to fit can cost as much as up to $229. These filters can be quite pricey but they are worth their weight in gold.
So do you just screw on your filter and point your camera at the scene you want to capture an that's it? Well not exactly. For starters if you look through your viewfinder or if you prefer Live-View with the filter on then you're not going to see much. In fact you'll be pretty much staring at black image. Metering a scene with your 10-stop filter attached will cause some problems too. The best method is to work out your composition and expose for the scene before you attach your filter to the lens.
Start by composing the scene how you want it, with the ISO, aperture setting and shutter speed required dialed in for the final shot. Then make a test exposure and check your histogram to ensure the image isn't overexposed. At this point you'll want to make a note of the shutter-speed without your 10-stop filter attached.
Now there's a bit of calculation here but nothing you'll need to worry about. Let's say after setting up your scene your camera's exposure meter is telling you that using an ISO of 100 and aperture of f/11 you need a shutter-speed of 1/15 of a second to gain the technically correct exposure. You now have to slow your shutter-speed down by 10-stops. This means by adding our 10-stop filter our shutter-speed now has to be altered to 60 seconds to achieve the correct exposure.
If you're like me and not much of a math whiz, there are several apps for your iOS or Android phone that can easily calculate the correct setting according to the density of the filter used. Check out the Lee Filters Exposure app or NiSi Filters Australia.
One thing to be aware of when using a ND filter is the color cast. Even the most optically perfect ND filter can suffer from some form of color shift when using a 6-stop or higher filter. The most common issue I've experienced a magenta color cast caused by infrared light still passing through the filter. For the best results you should always shoot in RAW mode and at your camera's lowest ISO setting.
As always, experimentation with various shutter-speeds is key. Be on the lookout for some familiar daytime moving objects (cars, bicycles, clouds, water, or people) that could look quite surreal if captured with a long shutter-speed. This exposure technique has been employed by many professionals to magically empty city landscapes filled with cars and people by using very strong ND filters. Now that you know it's up to you and your imagination to take control of your creativity and give your daytime shots a twist with some long exposures.