As the image sensor performs imaging by reacting to light, the camera is unable to capture anything in a pitch-dark location even when the shutter is open. However, with the use of a flash, an image can be captured at the instant the flash is fired. In other words, in the dark, the flash unit plays the role of the shutter. In this article, I will introduce photographic techniques that make good use of this characteristic of the flash unit. (Reported by: Koji Ueda)
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Capturing Movement in a Photo with Continuous Flash Firing
Stroboscopic flash is a feature that exposes the subject for a multiple number of times within a single shot by firing the flash continuously. Among Canon's external flash units, those that come with this feature include the Speedlite 600EX-RT and Speedlite 580EX II. In stroboscopic flash photography, you can specify the number of flashes per second, or the total number of flashes. However, note that the flash count is also subject to the flash output. First of all, the location must be one where you can at least vaguely identify the subject. Since it would not be possible to adjust the focus according to the subject's movements, you have to fix the point to focus in advance.
EOS 60D/ EF-S18-135mm f/3.5-5.6 IS/ Manual exposure (f/8, 4 sec.)/ ISO 100/ WB: Auto/ Speedlite 580EX II (Manual, 1/16)/ (Stroboscopic flash) firing frequency: 1Hz; flash count: 3
The shot was taken indoors at night with the lights turned off. The silhouette of the subject could be vaguely identified. I secured the camera on a tripod, and directed the Speedlite on the subject. I covered the background with a piece of black cloth to prevent any unwanted objects from being captured. I set the flash count to , followed by setting the firing frequency to [1Hz].
Position of the subject, camera and Speedlite
A: Approx. 2m
B: Moves after each firing
Steps for Using Stroboscopic Flash
1. Select a shooting mode
The Manual Exposure mode is recommended, as it is easier to fix the shutter speed according to the flash count, and the depth-of-field can also be controlled easily.
2. Set the focus
As the shoot is carried out in a low-light condition that is almost pitch dark, fix the focus in advance with MF.
3. Determine the flash count
Determine the flash count according to how many times you want the subject to be captured in a single photo.
4. Set the firing frequency and shutter speed
The firing frequency (Hz) determines how many times the flash is fired per second. After doing so, set the shutter speed based on the duration up to the end of the stroboscopic flash. Next, release the shutter according to the movement of the subject.
Tips for Using Stroboscopic Flash
1. Do not place any object in the background
During stroboscopic flash photography, it is important that you do not place any object behind the subject. When capturing multiple-exposure shots, objects in the background may overlap with the subject, resulting in a disorderly image. The background should therefore be simple, such as by using a wall. Also, note that a white wall may cause the subject to appear translucent. In this case, you can attach a piece of black cloth or paper to the wall.
2. Set shutter speed according to the number of images to capture in a photo
You need to determine the firing frequency (Hz), flash count, and shutter speed based on how many times the subject is to be captured in a single photo. For example, if you want to capture the subject for a total of three times within a single photo, with each image captured at an interval of one second, set the firing frequency to 1Hz and flash count to 3 times. In this case, set the shutter speed to 3 seconds. Simply bear in mind to set the shutter speed according to the firing frequency and flash count.
3. Move the subject horizontally with respect to the camera
As stroboscopic flash photography takes place in an almost pitch-dark location, it is impossible to adjust the focus according to the movement of the subject. A fixed focus needs to be set in advance. Bear in mind that by having the subject move sideways with respect to the camera instead of backward or forward, you will not have to worry about the focus going out of alignment. In case the subject moved slightly to the front or the back, stop down the aperture as much as possible so that focus can still be achieved.
Born in Hiroshima in 1982, Ueda started his career as an assistant for photographer Shinichi Hanawa. He later became a freelance photographer, and is now engaged in a wide range of work from magazines to commercials while shooting different cities and landscapes all around the world. He is also a writer and a lecturer at photography lectures and workshops.