Why use flash instead of continuous light bulbs for photography?
Asked 11/19/2012
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Why are photographic flashes or strobes commonly used to light a scene instead of ordinary continuous light sources like household bulbs? What advantages do flashes have for photography?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
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The use of flash actually pre-dates electric lighting, the first flashes being entirely chemical.
Nowadays the main reason for using flash is that a flash can be considerably brighter than continuous lighting because it only has to be on for a very short time (while the photo is being taken).
A continuous light source that was the same brightness as a flash would consume a huge amount of energy (and get exceedingly hot during the process). Fluorescent lighting has come on a long way and produces much less heat but at high power output can still cook your subject. As it stands a simple hotshoe flash can produce many many times the light intensity of a mains powered bulb, despite running on AA batteries because it is only on for one thousandth of a second. The flash works by charging a capacitor slowly and releasing all the energy in a single burst.
Other than the greater quantity of light (which enables you to use a lower ISO, and to light a larger area) there are other advantages to flashes:
The low power consumption makes small portable battery powered flashes possible.
The short duration allows you to freeze motion as any subject motion after the short burst of light will not be recorded.
The shutter speed independent nature of flash allows you to tune the balance between flash and ambient light. Aperture/ISO have an effect on both flash and ambient brightness, shutter speed only effects ambient brightness, by changing shutter speed an compensating with aperture you can alter the flash/ambient light balance.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
13y ago
0
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Flash is used because it can deliver a very large amount of light in an extremely short burst. That gives photographers enough illumination during the exposure without needing a continuous light source that would use far more power and generate much more heat.
Compared with ordinary bulbs, flash has several practical advantages:
- very high light output for a brief moment
- lower heat on the subject than equally bright continuous lighting
- efficient use of battery power because it only fires during the exposure
- the short burst can help freeze motion
Traditional tungsten bulbs are inefficient and warm in color, and powerful ones get very hot. Some fluorescent lights are more efficient, but can have color issues and flicker, which can be a problem at certain shutter speeds.
That said, photographers do not always use flash. Modern continuous lights can work well, especially with today’s cameras handling higher ISO settings much better than older film or early digital cameras. Continuous lighting is often preferred when you want to see the lighting effect in real time. But when you need a lot of light efficiently and briefly, flash is usually the better tool.
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