Negative Shutter Offset in Physical Camera?

[Monogon]

Hi there,

i am trying to match motion blur with some footage and there is a render offset which needs to be shifted into the negative direction. the max physical camera only allows >0 and positive values only make it worse.
(without motion blur everything matches perfectly, and with the visually correct amount the rendering shifts on the footage..
whats the the best way to fix that?

thx
felix

[joconnell]

Normally when I'm working with tracked footage where you want to center the motion blur on the frame and not half way between the one frame and the next (like you're rendering frame 0.5 1.5, 2.5 and so on) I apply motion blur in the render dialog set to a duration of 0.5 for a 180 degree shutter and use the interval center command set to 0 so that the motion blur centers itself around the frame itself and your objects stick. The only thing to watch out for is vray needs an object to come from somewhere and go to somewhere else to know what direction it's travelling and create blur vectors. Say if my tracked footage starts at frame 0 and goes to 100, I can't track any frames earlier than 0 (cos they don't exist) so when vray tries to make motion blur for frame 0, it's got no info about where the objects have come from. The way to get around this is if you make all the keyframes on frame 0 (or your first frame) linear and then use the max out of range types set to linear, the animation will just continue whatever way it's travelling in the frames before and after your track - it'll give vray enough infor to blur. Like wise if you have a camera animation, make sure it's got a frame before and after your shot length with animation.