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How is the circular motion blur created in this picture?

Is it a result of rear-curtain sync? If so how does one accomplish this?

enter image description here
Original image

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  • Slow shutter time
  • Short duration flash
  • Rotate the camera around the optical axis of the lens

The dancer is only lit by the very short flash burst, the background is lit by continuous ambient lighting for the much longer exposure time as the camera is being rotated around the lens' optical axis.

Slow Shutter I'd start somewhere in the neighborhood of 1/15-1/30 second. Adjust from there as needed. They key to getting shots like this is to practice them beforehand and find what shutter times work for the way you handle the camera.

Short Flash Compared to the shutter time you'll use for a shot like this, pretty much all small, portable shoe mount type flashes are short duration as long as you're not using them in High Speed Sync (Canon)/Auto Focal Plane (Nikon) mode which tends to act like continuous lighting when the shutter is open. Ironically, with a typical shoe mount flash (even when used off camera) the lower the power setting the shorter the duration of the flash which can make it easier to freeze your subject if there is little to no ambient light falling on the subject. With small portable flashes intensity of the light follows the same pattern regardless of the power setting. Power, i.e. the total amount of light created, is reduced by shortening the length of the flash's duration. So lowering the power is the same thing as shortening the duration. Even at full power, most speedlights have a maximum duration of around 1/1000 second, give or take a stop, which is well above the typical shutter sync speed of 1/200-1/250 for many DSLRs. At lowest power most flashes have a shorter duration than most camera's fastest shutter speed. Keep in mind that with a focal plane shutter even a shutter time of 1/8000 second takes about 1/300 second for the slit between the first and second curtains to transit the sensor (or film).

Camera Rotation It takes a little practice to learn how to rotate the camera while keeping the center of the lens pointed in the same direction. How fast you rotate the camera and how long you leave the shutter open determines how long the blur lines from the ambient lights are. If you don't want circles you can move the camera in other motions.

For more about dragging the shutter, please see:
Why does the flash freeze a picture?
When should you use a normal flash vs a second-curtain flash?
Why doesn't a shutter speed of ¹⁄₂₅₀th freeze motion when a flash of that duration does? (particularly this answer addresses the concerns of your question)
Why does flash decrease motion blur?
Photographing a waterfall but also have a person in foreground

  • Can you clarify what short duration means? A manual strobe doesnt let me control duration, only power and zoom. Secondly, would this require a tripod? I tried it hand held but the entire image is blurred. Keeping in mind that the flash is a manual one and shutter was 1.3s. Thanks in advance! – Chai Jan 2 '17 at 21:38
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    Answer edited to address first follow up question. I was trying to keep it short and sweet. :-) Unless you are using a lens with a tripod collar attached to the tripod (rather than the base of the camera) that allows you to rotate the entire camera around the lens' optical axis while mounted to a tripod you can't do this from a tripod. – Michael C Jan 2 '17 at 22:00
  • "With small portable flashes the peak is just as bright regardless of the power setting." That's not true. The flash discharge curve is the same regardless of power setting, and the flash does reach peak brightness pretty early in the discharge, so it is true for higher flash power settings. However, for very low power settings the flash will shut off ("quench") before it reaches peak power, thus reducing peak brightness. Total light output is the area under the intensity curve, which is decidedly non-linear. – Duncan C Jan 3 '17 at 1:22
  • See the chart in this link: photo.toomastamm.eu/flash-discharge-regular Note that at 1/16 power, the example flash does not reach full intensity. – Duncan C Jan 3 '17 at 1:49
  • @DuncanC Any power settings that cut the flash off before it can reach peak don't really have a peak - they're still building up to a peak when they are cut off. It doesn't serve any purpose whatsoever to have to explain what a flash discharge curve is to the OP who just wants to know how to take a photo like the example. I didn't even want to get into the relationship between duration and power levels. LOL – Michael C Jan 3 '17 at 2:41
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It looks to me like they dragged the shutter. That is they set the shutter speed to something longish, but then used a flash. The model is illuminated by the flash with the camera still. Then after the flash has finished, the camera is rotated around the frame's center causing lights in the background to form the radially blurred pattern you see. The model is no longer illuminated at that point, so she doesn't contribute to the blur.

  • Thanks for your answer. How long are we talking? I tried 1.3s with no good results. – Chai Jan 2 '17 at 21:39
  • I'm not sure just from looking, but I wouldn't think you'd need to go over a second to get a similar result. It may depend on the brightness of the other lights and how dark the model is. It looks like she's in a club in that picture, and clubs tend to be really dark (usually no windows). It also occurs to me that there's a possibility she's standing in front of some sort of spinning set of lights. Perhaps the lights are moving and not the model? It's hard to say since it's such an abstract shot outside of the model. – user1118321 Jan 2 '17 at 23:10
  • I call BS. Yes some of the image is created by rotation. The background lights are exposed the whole time the shutter is open and the flash exposes the model for less time than that. But neither explains that red blocky nebula. Arc lengths should get smaller the closer to the center of rotation but should streak over the same angle. Things that emit their own light will be longer than things the flash lights up. Neither should be producing a blocky nebula. – candied_orange Jan 3 '17 at 13:35
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    @user2440943 1.3s is certainly too long.. try like 1/60..maybe even 1/125 – John Easley Jan 3 '17 at 19:54
  • A follow up. Wouldn't flash before rotation cause the model to blur? I think rear sync makes more sense here. Interested in your opinions on this , thanks! – Chai Jan 7 '17 at 12:57
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The photographer is rotating the camera along the axis of the lens.

What you see in the background are various lights. The amount of background motion blur is a function of shutter speed vs how fast the photographer is twisting the camera. If you twist faster, you can have a faster shutter speed, and visa versa.

The model is illuminated by flash. A flash is by nature a very fast burst of light. That's why she is mostly frozen (though not entirely -- look at her legs).

Just spin the camera -- the flash will freeze whatever it illuminates, and constant lights and everything illuminated sufficiently by them will blur.

Starting point: Try 1/8th of a second exposure, and adjust from there to get the desired amount of motion blur. Either spin the camera faster or slower, or set the exposure longer (though probably not shorter).

Flash: I think any flash will give you the desired effect. They are all by nature short flashes of light. Some flashes such as Speedlight are even faster if used at reduced power.

Adjust aperture and ISO to get the desired exposure.

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