YS-D1 -- What's the difference between Manual and TTL?

[Matt S.]

If I set the aperture/shutter manually on my camera (Canon S100), and set the YS-D1 to manual, I get good exposures. I can also use the compensation dial on the strobe to adjust output power.

How does the system know how much light to produce for a good exposure, and how is this this different than when the strobe is on TTL?

 

[Meni Meller]

The system doesn't know how much light to output in manual mode.
when the strobe is on a manual mode, you use the dial to tell it how much light to output, meaning that when the dial is centered -- same amount of light will be outputed regardless of camera to subject distance and exposure settings.
it appears that you got lucky, and the middle position resulted in the right amount of light for your shooting condition.


in TTL mode, the dial in its centered position will cause the light output to adjust its level based on exposure settings, camera to subject distance, metering mode, etc...
in that case, setting the dial will actually cause a compensation to take place, rather than an absolute light level output on manual mode.

your camera doesn't support TTL on M mode, you will therefore need to use Different mode and set your internal flash to TTL as well to get your strobes to fire at TTL mode.

hope this helps