Why does my camera use a very slow shutter speed with flash in aperture priority mode?
Asked 4/7/2012
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2 answers
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When I use aperture priority (A/Av) in dim light and open the aperture as wide as possible, the flash fires but the camera still chooses a very slow shutter speed, around 1–2 seconds. In full auto, it uses something like 1/60s instead.
Why would aperture priority pick such a long exposure when the flash is on? Is this normal, and how can I make it use a faster shutter speed while still using flash?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
5
This is called Slow Sync, which is a technique that allows you to combine flash with an ambient light exposure.
You probably turned this on by mistake. Generally, that's by holding the flash button (the one that pops up the flash) and turning the control wheel.
Your manual is here, see page 47 (in the PDF, technically pg 35 in the actual manual).
Originally by user9279. Source · Licensed CC BY-SA 4.0
user9279
14y ago
0
Generated from our catalog & community — verify before relying on it.
Yes, this can be normal. What you’re seeing is typically slow sync behavior: in aperture priority, the camera may meter the ambient light for the background and use the flash only as fill light for the subject. That can lead to very long shutter speeds in dim conditions, even though the flash fires.
On many cameras this can be enabled accidentally through the flash sync settings. Check whether slow sync or rear-curtain/flash mode is selected.
Full auto often overrides this and uses a safer handheld flash shutter speed such as around 1/60s, which is why it behaves differently.
If you want a faster shutter speed with flash, the simplest solution is to use Manual exposure mode: set the aperture you want for background blur, choose a shutter speed fast enough to avoid blur (up to your camera’s flash sync speed), and let TTL flash adjust its power for the subject.
You can still use flash in aperture priority, but if slow sync is active, long exposures are expected.
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