Since long time, photographers have used slow shutter speeds to convey movement in their photographs. A blurred image can convey movement and sometime the speed of the movement can also depend on the amount of blur. The basics for creating motion blur are simple. The only limiting factor is the creativity.
Slow shutter speed is the key concept. This can be achieved by using a small aperture (high f-number), low ISO and with low ambient light. In case of high levels of ambient light, dark filters can be used to be able to click at the slow shutter speeds. Manual mode works the best. Shutter speed can be set as per the movement to be captured and aperture as per the available light and depth of field that is required.
(Water has always been my favorite subject for motion blur. This photograph was captured on film and then scanned on an inexpensive scanner. Notice the thin streaks of water. A longer shutter speed would have obliterated these streaks and a faster shutter speed would not have shown the motion blur so beautifully)
How to get good motion blurs?
Shutter Speed – To get a good motion blur, the shutter speed should be slow enough for the movement to occur. This is obviously the basic requirement. The key concept here is that the movement being discussed, is in reference to the frame size. A person walking across the image frame will appear to be more blurred when the person occupies a substantial part of the frame, than when the same image is captured from a distance and the person is comparatively a small part in the frame. The movement of the subject that is to be shown should actually be significant in comparison to the frame size. The shutter speed also depends on the speed of the subject movement. A slow moving snail will require a slower shutter speed than a fast moving car to get motion blur.
Stabilize your camera – Use a tripod wherever possible. Completely blurred photographs may look good as an abstract, but to show motion, ideally some reference points should be sharply in focus. If it is a waterfalls, get the rocks and vegetation in sharp focus and let the water be blurred. If it is a street scene, get the buildings and other landmarks in sharp focus. Reducing the inadvert camera shake while on tripod is also very important. Either use mirror lock-up functionality or use live-view to lock up the mirror before taking the shot.
Problems with long exposure time – Very slow shutter speeds (extending over few minutes) are prone to problems. Digital sensors can heat up and produce long exposure noise. Film can exhibit reciprocity failure. Consider these factors when you plan your long exposures. I use DSLRs almost exclusively now a days, so for me the most important concern is to keep the camera cool in such long exposures. Even when I have to use live-view to lock-up the mirror, I use this function for a very short duration. Keeping the sensor cool requires some quick thinking once the live-view mode is switched on. So plan and set everything using your optical viewfinder before switching on the live-view. Long exposure noise reduction helps but not in a manner I would like it to.
Cover up the eyepiece too (that end of optical viewfinder from where you look inside). Light can leak from this and spoil the photograph.
Metering Mode – Metering is another challenge that needs to be taken care of. I recommend using center weighted metering or spot-metering for long exposures. Evaluative metering (3D Matrix) gives inaccurate readings with dark filters. Sometimes the exposure may fall outside of the metered range of shutter-speeds, like when using B (Bulb) mode. My method is to calculate the exposure with open aperture (small f-number) and high ISO, and then close the aperture and also reduce the ISO. The total number of stops these two are reduced can then be used to increase the shutter opening time in the same number of stops. Thinking in terms of f-stops is the key to getting the correct exposure every time. If it is night scene, expose in a manner that the darkness doesn’t get over exposed. Night shots which have a grey overcast look ghastly.
Focal length – Focal length of the lens should be good enough to show the movement in the frame. Too short a focal length will not show the movement very effectively, as discussed earlier along with shutter speeds. When the movement takes up a small area in the frame, then the exposure time required has to be very long. Seascapes where the whole sea-surface is blurred, requires exposures extending to many minutes. The waves forming on the sea surface are very small when the whole scene is considered and so the really long exposure time. On the other hand, a waterfalls located at close proximity will look good even with a few seconds of exposure.
Subject – The impact that a motion blur photograph generates, depends on the subject too. The more blurred the subject appears in the photograph, faster the movement it conveys. A blurred image of a person walking in front of a building or light trails of cars rushing by in the evening, convey a feeling of faster movement than was actually present. This is due to our perception of our surroundings. When a car rushes by in front of us, it is very hard to make out all the details. On the contrary in a parked car, even a small scratch on the bumper is noticeable. For large water bodies the opposite holds true. Sufficiently blurred seascapes make the water look serene and quiet. This also has to do with our perception of the real world. When the weather is not windy, the water appears still. So the motion blur photographs of sea convey a very quiet weather. Decide on what you want to convey with your photograph before pressing the shutter release button.
Focus – Using a small aperture gives the added advantage of increased depth of field. Use manual focusing if you are planning to use ND filters. Even a ND filter that cuts 2 to 3 stops of light can make the autofocus inaccurate. With very dark filters, it may not be practically possible to focus using the viewfinder. Screw the filter on after focusing. Livewview if available, may help, but remember that using live-view heats up the sensor and also eats up battery power.
(At 1/4 of a second, the water is quite blurred in the image below. At almost the same shutter speed in the photograph on top, the blurring is not so significant)
To show the motion blur in the best quality –
Do not expose to get the maximum blur. Photographs like waterfalls, cascades, people moving on streets or even a rushing vehicle – all these look good when some amount of outline of the subjects is visible. Blurred blotches without any context of the scene, kill the look.
Do not expose in a manner that the movement ends prematurely. This is opposite of what I have written above. The intention is to get the movement to occur completely during the exposure. A shortish ‘long exposure’ may give an impression of camera shake rather than motion blur. It can be quite distracting too. I remember an instance where I captured images of a rotating ferry wheel. Too long a exposure created just a blur with no recognizable subject. Too short a exposure created an image which appeared blurred due to camera shake and was stressful to look at. (Unfortunately, I do not have those photographs with me now).
Meter for the shadows in dark photographs. Light trails on highways pose a challenge when one side of the traffic is visible from the front and the other side from the back. The front facing traffic has headlights which appear to be far brighter than the side that has red tail lights. When in doubt, expose for the tail lights and the static landmarks on the road. Do not worry about the headlights getting overexposed.
Experiment with slow-sync flash. This helps to freeze a moving subject at the beginning or end of the exposure. Read about it here – Flash Modes
(The head of the butterfly and the antennae are in focus but the wings have motion blur)
When not to blur?
There are a lot many things that loose their impact when these are blurred. So do not try motion blur photographs with these –
Fog, snow and rain – These just appear as areas of low contrast in the photograph or sometimes as white-grey patches. (Fog – Capturing its Mystery)
Clouds – In exposures lasting for over half a minute and even for shorter exposures on a windy day, clouds can appear to be moving across the frame at a fast speed. For some this may look attractive and for others it may kill the photograph. It’s your photograph so you decide.
Flying birds and airplanes when viewed from below (where the background is without any reference points) – The motion blur looks like a poorly captured photograph with faulty technique.
Sun – In seascapes especially, where the exposure time is very long, the sun will appear elongated due to its movement. Try to keep sun out of your composition if the exposure time is going to be very long.
Portraits – Dance movements, acrobatics and even golf swings look fine as motion blurs but if the main subject is on the person, then either use a fast enough shutter speed to freeze the face or use a slow-sync flash.
(River – Using dark ND filters helps in vast spreads of slow moving rivers and seascapes since the movement with respect to the frame size is minimal. For a good motion blur, really long exposures are required. Refer this article for more information on ND filters – Neutral Density Filters)
Using photo-editors for motion blur
This is the latest in creating motion blur photographs. The principle is to superimpose multiple photographs of the same scene. The things that are in movement have a different location in every frame. Algorithms are used, making use of this information. A composite photograph then gets created showing the motion blur. This is an interesting method and takes care of the various challenges that pose themselves while actually capturing motion blurs. The drawback with this technique is that the results can sometimes be very unpredictable and may even look artificial.
(Nikon Df with 135mm lens, f/18 at 1/15 sec. I was without a tripod. The challenge was to keep the camera stable with the 135mm lens mounted on it so as to get the rocks in clear focus and yet have a low enough shutter speed to get motion blur from the flowing water. The blur is not as good as I would have loved to capture but with the limited equipment that I had, this one serves the purpose. Sometimes having a sharp image is more important than the motion blur of the moving object.)