Keen eye'd observers may have noticed that some of our work has featured an awesome looking effect that keeps the subject in clear focus, while creating motion blur that sometimes seemingly blends into the in focus parts of the image; or images where the motion of people walking through the frame is blurred while the background and other elements of the image remain largely in focus.
In this guide, we're going to run through how to create that motion blur effect.
The shutter drag effect
The first effect, and is one we're often questioned about, is known as the shutter drag effect. And no, achieving this effect doesn't require doing a double exposure or anything fancy like that.
It's called 'dragging the shutter' as that's what you're doing in order to achieve it: you're moving your camera on purpose, using a slow shutter speed combined with a camera flash, to create the motion blur effect while keeping your primary subject/s in focus.
What you need in order to do this, at minimum, is:
- A camera flash - the settings of which can be adjusted.
- A ND filter (if you're wanting to achieve this effect in brightly lit settings).
- A wide angle lens.
What you do is you set your camera to a slow shutter speed, 1/30th of a second or slower; and set the intensity of your flash depending on the amount of ambient light; while also adjusting your camera ISO settings accordingly as well to get a well exposed image. For your camera flash: you shouldn't need to change your flash sync settings from the default settings; but you can also use its rear sync settings.
Focus on the part of the image, or the subject, that you want in focus, as normal. Then as soon as you press the shutter button, move the camera.
If you've timed it right, you'll get a resulting image where the subject/s are in focus, with motion blur effects. For example: if you spin the camera in a circular motion, you'll get a circular effect in the image centred on the centre of the image. If you move your camera to the left, you'll get motion blur effects in the image that look as if they're moving to the right of the image. And so on.
This may require a bit of trial and error, especially getting the camera flash intensity right and timing the movement of your camera.
You can also try using slower shutter speeds, noting that the slower the shutter speed, the more exaggerated the effect will be; but at the same time it's also easier to time.
The technical side: how it works
This works because, from a technical standpoint, the flash acts a 'second (very fast) shutter and freezes the frame. In it's default setting, the camera flash will fire as soon as you press the shutter button on your camera. Your camera's shutter remains open for longer than the flash takes to fire. As such, after the flash has fired, the parts of the image not illuminated by the flash can be affected by motion blur, just as any other long exposure image is.
Below is a visual diagram of how it works.
We mentioned the terms front sync and rear sync above. In its default setting (front sync), the flash fires as soon as the shutter button is pressed. In rear sync, the camera flash fires at the end of the exposure.
The motion blur effect
This effect can be achieved without using a camera flash, but you will need a tripod or other flat surface in order to achieve it.
The goal with this effect is creating a sense of movement across the image, while your primary subjects are kept in focus with as minimal motion blur as possible. However, if your subjects move, they will be blurred out too. So getting a good looking image with this effect can take some trial and error too - particularly in busy situations.
Achieving this effect requires a slow shutter speed, 1/30th of a second or slower, and good timing.
Keep in mind that the effects of motion are less pronounced the further away the subject is in the image. Hence: using a wide angle lens is advised. It's also possible, following on from the shutter drag technique, to set up a flash off camera if you have a wireless flash trigger/commander; using that to freeze the motion of your primary subject while having motion blur in the foreground.
This has been a short guide on how to achieve motion blur effects in photos while keeping your subjects clear. Give it a try, and let us know in the comments how you go.
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