You need to understand the concept of flash duration.
From what I am reading, I am sure that your shutter frame is not fully open at 1/250.
For speedlights, the less power is fired, the shorter the flash duration. When you are firing at TTL, you are probably firing at much lower power than 1/4 power, so the flash duration is shorter, causing insufficient light to light up the entire frame. There could also be a slight sync problem with your Di866.
Remember though, for Studio flash, it is the reverse, the more power you use, the shorter the flash duration.
BTW, when your shutter speed is starting to hit the edge of the limit like 1/250, doesn't HSS automatically kicks in?
I suspect it maybe a bit spoil already because my di622mk2 don't have these problems. I try not to do hss because I know that one eat a lot of power and I burnt my di866mk1 once already
In studio on white steamless I actually shoot at 1/125 instead of the max sync of 1/250. Because for every 50 shots, maybe 3 to 5 shots will have sync problem. 1/200 and 1/160 reduce the ratio down. Since I dont have problems of ambient, 1/125 totally eliminates the problem.
then i mount the 866 on camera body, still got black band. then i try put the di866 on optical slave mode (manual), also got balck band.....but it is ok, i 50% write off this flash already , can only use as support light
i wanna thank you and clubsnap. from here i learnt:
1) put camera manual mode (1/250 - kids super fast but i dont want to go hss), (iso 100 - for the cleanest photo), (f4 - f5.6: lens highest resolution aperture)
2) then lup 2-3 flash to mmet the extreme amount of light requirement of (1/250, iso100, f4)
i know this trick only can do indoor, but hey, it is good enough for most of my needs!
i also go and get 2 cheap small umbrella and i tink i will only use them once so far, i very satisfied with the result!
heh heh heh...i say until like flash is magic bullet
1. you do not need your shutter speed to be fast, because the flash duration is fast, and it will freeze the action for you even if your shutter speed is slower.
2. You should not shoot at ISO100. ISO performance on cameras are very good nowadays. If you have a moderately newer camera, your ISO can be pushed to at least ISO800 with negligible noise. WIth ISO higher, your flash do not have to work as hard. This will give you faster flash refresh rates, longer battery life, as well as faster flash duration (for speedlights only) that will freeze action better in (1).
Whoa!!!! i never knew about (1)!!! tonight i go home try 1/200 and so on progressively to see where the is confortable minimum.....
my one is 40d.... i notice that if i shoot at iso800 and above, there will be artifacts if i sharpen in dpp. but i notice that if i shoot at iso100, i cant see any artifacts even if i sharpen to +10....maybe i shoot iso400
later i go and google what is 40d optimum iso my son just call me this morning and told me that my 2nd set of yongnuo trigger has arrived, damm cant wait to go home today!
i ust went to do more read up and watch free tutorial in youtube. good stuff:
i learnt great new stuff today!!!
if manual settings on camera produce total black image,
effective shutter speed = flash duration
camera shutter speed is no longer the freeze motion factor
wow!!! i learnt about flash duration today!!! i think i kee siao liao !!!
Last edited by Mustank; 9th October 2012 at 05:37 PM.
i must have gotten my flash theory all wrong that it is aperture which controls flash lighting given a fixed flash power . . .
For example, if you are on f/5.6 an 1/250s right now - you want to cut flash power by 1 stop but retain ambient - you turn up aperture to f/8 to cut flash by 1 stop, then lower shutter speed by 1 stop to 1/125 to maintain ambient (since raising aperture from f/5.6 to f/8 cuts ambient by 1 stop too).