There’s a simple test to check if TTL works or not for sure:
Do the test indoors.
- Set ISO to 100
- Set a fast shutter speed – 1/1000 or 1/2000 (with a compact) or 1/250s with a DSLR / Mirrorless
- Set the strobe to TTL or S-TTL, with zero exposure compensation (usually power knob pointing up).
- Set the camera flash to Fill Flash, make sure it’s popped up
- Shoot two photos of a neutral subject (non-reflective!), zoomed in, from 2-3 feet away.
- 1st with a larger aperture – f/2 or f/2.8.
- 2nd with a small aperture – f/8 or higher if possible.
If the two photos come out fairly similar, not overexposed, then TTL works.
If the first is significantly brighter than the 2nd, TTL is not working and something is wrong with the settings.
Check this sample out to see how it should look like: http://www. housingcamera.com/blog/ underwater-flashes/ttl- underwater-strobes
If this test works, then TTL works, but it may not be completely reliable in all scene types. That’s how optical TTL is. TTL works much better and is more accurate for macro and close-up photos than wide angle.
If you’re getting over / under exposure in a wide angle scene with TTL, switch to manual flash and control your light as needed.
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