Why does my Nikon D7200 use shutter speeds below my Auto ISO minimum when an external flash is on in Aperture Priority?
Asked 8/16/2018
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On a Nikon D7200 in Aperture Priority, I have Auto ISO enabled with a maximum of ISO 6400 and a minimum shutter speed of 1/125. With no flash, or with the built-in flash, it behaves as expected. But when I use a Godox V860IIN external flash, the camera sometimes selects shutter speeds slower than 1/125 before ISO reaches its maximum. Why does this happen, and how can I stop it?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
1
The D7200 manual says that in A or P modes, the ISO menu Minimum Shutter Speed is the threshold concerning if ISO increases or not.
It does also say that in Auto Mode that the camera will choose Minimum Shutter Speed based on focal length, but that is only Auto mode.
But also, page 104 of the free larger D7200 Reference Manual also says that if flash is used, Minimum Shutter Speed will be set to either the E1 or E2 menu, as applicable (E1 flash sync speed, E2 slowest flash shutter speed in A or P mode).
In general though... Auto ISO action is this:
In A mode, as the light becomes more dim, the shutter speed drops to maintain proper exposure. When the shutter speed hits this ISO Minimum Shutter Speed, then the shutter speed is frozen there, and the ISO increases instead. However, when the ISO hits the Maximum ISO specified, the camera still must try to maintain a proper exposure, so then the shutter speed must drop even more.
In A mode, this ISO Minimum Shutter Speed should be given careful consideration, because, any time ISO is actively changing (anytime between Minimum and Maximum ISO), this is the shutter speed that will be used, every time.
But for D7200, if flash, then also see E1 and E2 menus, per that page 104.
Originally by user38978. Source · Licensed CC BY-SA 4.0
user38978
7y ago
0
Generated from our catalog & community — verify before relying on it.
On the D7200, Auto ISO’s “Minimum shutter speed” does not always control shutter speed when flash is active. In A or P mode with flash, Nikon uses the flash settings menus instead—especially the flash sync speed and the slowest flash shutter speed settings.
If a flash mode such as slow sync or rear-curtain sync is enabled, the camera may deliberately use slower shutter speeds to expose ambient background light. That’s why you can see speeds below your 1/125 Auto ISO minimum.
In your case, switching from Rear Curtain to Fill Flash solved it. That fits Nikon behavior: rear-curtain sync is often paired with slower shutter speeds, while fill flash keeps the camera from dragging the shutter as much.
If you want to prevent this:
- Use Fill Flash instead of Rear Curtain/Slow Sync.
- Check the D7200 e1/e2 flash menu settings.
- If you need full control, use Manual exposure mode.
Also note that flash sync speed is a separate limit from Auto ISO minimum shutter speed.
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