Have you ever wanted to capture clouds or water moving in your daytime photos but couldn't figure out how to make it work? The process isn't really that difficult, but you will have to invest in some gear. What you will need (besides your camera and lens):
- A sturdy tripod & head. These exposures are 30 seconds or longer, so you can't hand hold them.
- A neutral density (ND) filter. These filters block the amount of light reaching your camera's sensor, resulting in a need for slower shutter speed (which allows clouds and water to move!). I use a B+W 77mm 3.0, which gives you 10 stops of light loss. I find this much to be necessary for the bulk of my work, so although it's costly, I wouldn't go for a lower strength. Another option is the more expensive Singh-Ray 77mm (Thin Mount) Vari-ND Variable Neutral Density Filter, which allows you to dial in the intensity of the neutral density. I haven't used this but it gets favorable reviews. There are also some DIY options, which I haven't tried. Make sure you get the ND filter with the largest filter thread that any of your lenses has (the filter thread will be indicated on your lens with a "ø" and a number, like 77mm, 72mm, 58mm, etc.). If you want to use it on a lens with a smaller filter thread, you can buy a step-down ring (such as a 77mm to 72mm).
- Optional: circular polarizer filter. You may already have one of these, and it gives you another 1 and 2/3 stops of light loss. It will usually cause a little bit of vignetting at the wide end of your lens, but it can be cloned out pretty easily.
- Remote shutter release cable. I have used an off brand one and it didn't hold up very well. I recommend getting the one your camera manufacturer makes (and make sure it's the right one for your specific model), since you'll be using it a lot if you like using ND filters as much as I do!
- Bulb mode - most DSLRs and a lot of mirrorless cameras have this.
First, you need to find a good scene to use this on. In my opinion, clouds and moving water are the best subjects for neutral density filters, and if they are in the same scene, like the photo above, all the better.
Once you have you have set up your tripod, put your filter(s) on your lens, and attached your remote shutter release cable, turn off your image stabilization (if the lens or camera has it) and switch to manual focus. Then turn on live view (if your camera doesn't have live view you'll have to get the shot ready and then put on the filters) and zoom in on the scene to focus accurately. Next, check your settings. I usually put my ISO somewhere between 50 and 200. My f/stop, if it's during the day, is down around f/22. Some argue that this causes the image to be less sharp, but I fix that up in Photoshop. My exposure is in bulb mode (either a dedicated "B" mode on your mode dial, or sometimes in the manual mode, dial the shutter speed past 30 seconds and it will go to bulb - consult your camera's manual). There are a couple of methods to estimating what a good exposure will be, but more than likely you will need to try a few times to get it right anyway. If it's really sunny, 120 seconds is a good starting point. If there are no clouds in the picture and water is my main focus, I usually forego bulb mode, use Aperture Priority mode, and stop down the lens until the meter reads 30 seconds. That's more than enough time to get the water looking silky smooth.
A couple of caveats: ND filters usually cast a warm white balance on the photo. This can easily be corrected in Lightroom or Camera Raw by fiddling with the white balance sliders until the photo looks right. Be sure to shoot raw, or this can be very difficult to correct. Another potential pitfall is that ND filters tend to make the scene more contrasty (at least in my experience), so while you might expose the clouds just right, the foreground might be too dark, or the the foreground is exposed properly but the clouds are blown out. If this happens, take multiple exposures and make an HDR photo, or even blend them manually using layer masks in Photoshop. Another more expensive solution is to invest in a graduated ND filter that only blocks light at the top of the photo. Personally, I've had great success with the former method and I've saved a bundle not buying extra filters.
Using a neutral density filter takes practice to get right, and also requires the photographer to know his or her way around the camera. If this process seems overwhelming to you now, just start experimenting (especially at night where longer shutter speeds are needed, which is similar to what happens when we use an ND filter during the day). Once you get to know your camera's ins and outs you'll find using an ND filter a natural next step.
Some of my favorite photos taken using an ND filter: