Last Saturday, I did a little fun experiment with the speed of the shutter on the flowing water while keeping the other exposure parameters, Aperture and ISO value, same. I had seen some really nice photographs on the Internet with the milky effect on the water which inspired me to try something similar on my own. I really wanted to try this on a big water fall where the water volume and the current is high but one of the such area I know nearby was closed due to the bridge construction. I am planning to go there again after the construction is finished. Meanwhile, I tried something similar in a little creek near my area. It was a bright sunny day and the only way I could achieve a long exposure shot was by using a Neutral Density filter. Here is the list of the tools I used for this setup. 1. Nikon D700 DSLR Camera 2. Nikon 16-35mm f/4 Wide Angle Lens 3. 10-Stop ND Filter (To stop the lights so that I can use the longer shutter speed to get the milky effect) 4. Shutter Release Cable (It is recommended for a long exposure shot to avoid any camera shake. If you do not have one, you can use the 2 seconds timer on your camera) 5. Tripod (It is a must have tool for a long exposure shot) 6. Exposure Calculator App (To calculate the exposure after applying a ND filter)
After setting up the camera on the tripod, I measured the correct exposure (in a Manual Mode) before using a filter and took a shot. I used the widest possible focal length (which is 16mm on this lens) and chose the minimum ISO possible to avoid any digital noise. And since it was a sunny bright day, I didn't need a higher ISO anyway. I turned off the VR on the lens (really don't need when you are shooting on a tripod), selected an aperture value of f/11 and manually focused the lens to the infinity to get everything in focus through out the frame. With an aperture value of f/11 and ISO 100, camera meter gave me the correct exposure with the shutter speed of 1/8th of a second. Here is the first shot with those camera settings.
Focal Length : 16 mm ISO : 100 Shutter speed : 1/8 sec Aperture : f/11
Then, I applied a 10-stop ND filter on the lens and calculated the required shutter speed (using an app on the left side) to compensate the lights blocked by the filter. Since I left the ISO and the aperture values same, Exposure Calculator App gave me the shutter speed of 128 seconds as the right shutter speed to get the correct exposure. Most of the modern DSLR supports the shutter speed of up-to 30 seconds and if you need more than that, you have to dial into the BULB mode and open or close the shutter manually by pressing the shutter release button. But the cool thing about this app is that it gives you a stopwatch (at the right bottom corner) after you calculate the new shutter speed. When you are ready to take a shot, you can snap the shutter release button (with the shutter release cable) and then start the timer on the app at the same time. And when your timer goes to the Zero, you can release the shutter as well by releasing the button on the shutter release cable. When I took the second shot, I noticed that the shot was little bit underexposed. Then I took another shot without changing any settings but kept the shutter open for an additional 5 seconds than the app suggested. If you are shooting in a RAW, little bit underexposed image is far better than the overexposed because it is easier to bring the details from the shadow than from the blown out highlights during the post processing. The reason I got the underexposed image with the calculated time could be due to the changing light during the long exposure time or the filter coating variation or the programming on the app itself. Normally, I take the value given by an app as a base value and then play around few seconds left and right while monitoring the histogram chart on the LCD monitor until I get the correct exposure. Here is the second shot with the long exposure setting (notice the leaves movement and the person in a picture below which are the distractions).
Focal Length : 16 mm ISO : 100 Shutter speed : 133 sec Aperture : f/11
May be due to the amount of the water flowing in the creek and the current of the water, long exposure didn't produce very much dramatic effect that I was hoping for but there is some noticeable effect on the water due to the longer shutter speed. Some people prefer the first version with a shorter shutter speed and some prefer the second version. I am not sure which side of the aisle you are on but it doesn't hurt to try something new and out of the ordinary as long as you enjoy doing it.