Hi Jake,

Great question - there are so many different ways of adding flash into HDR/exposure fusion that I don't know where to begin! Since there are many 'right' ways to do it, I'll begin with the 'wrong' way and try and work my way back.

The biggest 'wrong' way to do this technique is to blend together multiple exposures at competing white balances, that's a recipe for a headache. If you utilize flash in one exposure but not the others, you're going to have to pay close attention to WB to make sure they line up. If you do it for all of them, it should be a little easier to manage.

So if you're using flashes on manual power, you can adjust the power of each flash between exposures - but that's your call. Some photographers prefer to work this way as that's their style of lighting, others will just pop flashes in during one exposure to cancel shadows and competing color casts. The most complicated implementation of this technique is where you change the location and power of the flashes between bracketed exposures - but this takes some serious practice as flashes don't give us the visualization that hot-lights do.

For a starting place, I would recommend just trying to hide a flash or two outside out of the frame and work on getting a natural-looking image as opposed to a 'flat' look that came from a flash. Once you get that down, there's really no stopping where you can go from there.

I hope that helps!