Quote Originally Posted by omaha View Post
I'll second what's already been said, and add that a ND filter can be quite useful in situations like this.

Bottom line for me is that if you want to take a quick snap in challenging lighting, then the modern TTL stuff (particularly, IMHO, the stuff from Nikon) is simply magic. Works a dream.

If you want to create a more composed and deliberate photograph, that's easily done too, but it takes more time and care. The essence of the problem is always that the ambient scene has higher EV than the subject. If you can't knock that down with a high shutter speed (you say you are locked in to 1/90s, but the same problem exists with any focal plane shutter camera), then a ND filter is a good option....if you have enough flash power to overcome it on the subject.
Thanks Omaha, I love the idea about the ND filters! I just remembered that I have a 1,2 and a 4 stop ND filter that would really help with this. However, I'll have to carry my bulkier but more powerful yongnuo YN 560 III to compensate for using the ND filter.

Regarding using TTL, I have a Nikon F3HP (heavier than the EM) and an SB 16a flash that TTLs (the flash can be used as a weapon because it's gigantic!) and these are my main reasons why I'm carrying the lighter EM setup while hiking. I should try it though.