tazdog said:
I was shooting in manual and my light meter was giving me a lower reading than it should have. I spoke to Sekonic and they said it was the pre flash. Are you sure that when you switch to manual that it also turns off the pre flash. It should like that would be correct but are you sure there is not switch?
In manual flash exposure there's no preflash. There's no switch for preflash.
If you'd like to test for yourself, enable mirror lockup. In that mode, the first shutter press locks up the mirror, and sets the flash exposure with a preflash. The flash for the image occurs when the image is captured with the second shutter press. With E-TTL, the flash fires at both shutter presses, with manual flash exposure it only fires with the second press.