Does TTL flash compensate automatically when I move or bounce an off-camera flash?
Asked 5/7/2013
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If I use a TTL-capable flash off camera with a radio trigger, will the camera automatically adjust flash output when I change the flash position or distance from the subject? Also, if I rotate the flash head and bounce it off a wall or ceiling, will TTL try to compensate and maintain the same exposure, assuming the flash has enough power?
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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Yes. This is an advantage of through-the-lens metering, as the effect of the flash is judged based the light that, well, actually comes through the lens. It doesn't need to know anything fancy about angles; it just measures the effect on exposure. (on modern systems, using a low-powered "preflash" to test, and calculating from that).
This can be fooled by reflective surfaces, but in practice I find (and I've heard others also observe) that it's actually more accurate bounced than with the flash pointed straight ahead (probably that reflection issue).
Of course, this will only work if your radio trigger understands your camera's TTL system. Some do, but most don't.
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
13y ago
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Generated from our catalog & community — verify before relying on it.
Yes—TTL generally compensates for changes in flash distance, position, and bounce angle because it meters the flash through the lens, usually by firing a quick preflash and calculating the needed output before the main exposure.
So if you move the flash farther away or aim it at a wall/ceiling for bounce, TTL will usually try to increase or decrease flash power to keep exposure consistent, as long as the flash has enough power available.
A few caveats:
- TTL is reacting to the metered preflash result, not directly to flash distance or head angle.
- Reflective or unusual surfaces can fool the meter.
- You may still need to set flash exposure compensation or adjust ratios between flash groups for the look you want.
- This only works if your radio trigger supports your camera’s TTL system; many triggers are manual-only.
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