Simulating shutter speed in Vegas

farss wrote on 11/7/2005, 4:13 AM
Try using event pan/crop to move a graphic element quickly across the frame and it plain don't look right. I've wrestled with this problem, tried Supersampling and Motion Blur, all to no avail. Nothing that I can do makes it look like what it would if I panned a camera across a printed page at the same rate.
Problem is of course a camera has a shutter speed of 1/50th of a second, the effective 'shutter' in Vegas is infinitly quick.
Have I missed something obvious here?
All that Supersampling does is create trails of the same frame, motion blur just composites x frames, problem is none of the frames contain any motion blur within them like they should.
This really sticks out in this current project as the material is all film originated and my simple fly in text sucks. There's got to be a way to do this, I've seen it done, maybe I'm using the wrong tool.
Bob.

Comments

PeterWright wrote on 11/7/2005, 4:37 AM
Have you tried with Track Motion Bob?
backlit wrote on 11/7/2005, 9:10 AM
Have tried getting away from "linear" motion?
farss wrote on 11/7/2005, 10:56 AM
Just tried both of those. Perhaps what I forgot to mention is that I'm rendering this as 25p. Rendering as 50i it looks as smooth as a babies bottom.
Reason for the 25p render is I don't want any interlace artifacts as this is going up on plasma / LCD displays. I can get it to look just fine rendering as 50p but that doesn't do much good as it's got to be delivered on PAL DVDs.
Adding Linear Blur helps but that still doesn't look quite right.
Other odd thing is this, if I get the graphic to move across the frame in 1 second and render at 50i it looks fine. Move the keyframe so it now takes 2 seconds and render as 25p it still looks jerky. I'd have thought one would offset the other but no such luck.
Bob.
farss wrote on 11/7/2005, 12:17 PM
I can get almost acceptable results by first rendering at 50fps (double PAL in Vegas). Then bring that into a new project, apply a few frames of MB and a little Linear Blur with some key frames to control it. Being able to render at say 200fps would probably get better results but looks like Vegas only allows certain frame rates, why is that?
Surely it cannot be that hard to do what a film camera can do!

Just so anyone trying to help understands what I want. Some graphic flies across the frame in a blur and comes to a quick stop. The fast motion should generate a pretty smooth blur that trails off as the object slows down and stops.

Gosh, maybe I should practice what I preach, if you want it to look like film, shoot film. And to think I could have bought an animation system (minus camera) for scrap metal prices some time ago.
Bob.
DrLumen wrote on 11/7/2005, 7:19 PM
Maybe try a slight gaussian blur on each frame before the motion blur?

intel i-4790k / Asus Z97 Pro / 32GB Crucial RAM / Nvidia GTX 560Ti / 500GB Samsung SSD / 256 GB Samsung SSD / 2-WDC 4TB Black HDD's / 2-WDC 1TB HDD's / 2-HP 23" Monitors / Various MIDI gear, controllers and audio interfaces

apit34356 wrote on 11/7/2005, 10:46 PM
Farss, remember that motion is a directional vector. But when you pan a camera, you not only adding a motion vector but are changing the lens effects and reflected light from the images in the field of view. There are many ways to produce the this effect, though, I don't remember off hand a quick solution for vegas that produces commercial qty end product.
Grazie wrote on 11/7/2005, 11:16 PM

Bob - your wanting a filmic experience so "why not shoot film" was the wake up call for me! You've started to analyze WHAT you want, I think the next approach may GIVE what you want - that was because I started to think along filmic lines and develop the layers, digitally . .ok

2 tracks?

Track 2: The movement of the Text: Motion Blur

Track 1: The "refocusing" or coming clear of the text

This way you've got control over movement and inter movement key-framing - Track Motion here?

. . thinking about it why not 2 events and a controlled Transition envelope to create that refocusing "dissolve"?

I also thought about the render high 50, re-import 25.

Any good? Could be the canine's proverbials?

Grazie

farss wrote on 11/8/2005, 12:34 AM
Grazie et al,
motion blur in Vegas simply doesn't cut it, here's why.
Lets assume we're shooting film at 25 fps, just to keep the maths simple.
A film camera has a 180deg shutter, that means the shutter is 1/50th of a second. Now let's assume an object crossed the field of view in that same time, what will the camera record? Well if it's lucky enough, nothing, if it sneaks past while the shutter is closed. However if it starts to cross the field of view just as the shutter opens then we get a streak right across the frame. It's a little bit more complex than even this because the shutter I think doesn't even start to expose the whole frame instantly nor does it block the whole frame all at once so so parts of the frame are exposed slightly more than the rest, so our streak may have comet tails etc. Lets just ignore that issue though.
Now what happens in Vegas using track motion.
Well in the above example if you tried to simulate that you'd never see the object fly past. If in frame 1 it's off the LH side of the frame and in frame 2 it's off the RH side of the frame then what's going to capture it? Bear in mind I'm asssuming we're working in 25p here, in 50i we'll get one field with it in the middle of the frame, hardly a filmic view of the object!
Now Vegas does attempt to address this problem by providing Supersampling. That computes the position of objects moved using track motion at intermediate positions between frames, creates intermediate frames and composites them together. It's a good try but for fast motion hardly adequate. 20 frames of Supersampling gives 20 snapshots across the field of view in the above example, again it sure isn't a streak. Technically you'd need at least 720 slices between the two frames to come close, I'd guess to generate sub pixel rendering increase that by an order of magnitude. Now that's one huge amount of calculations just for two frames, I'd bet the render times for a minute of video with that level of accuracy would be hours.
Now I do have one way to try getting the right result. Run the project at say 1/100th the final speed. Create 100 copies of the track and offser each one by one frame, set the composite level of each to say 1%. Render that out (if it ever does finish!) and then speed the whole thing up 100 times.
Bob.
Serena wrote on 11/8/2005, 1:08 AM
Bob, around this time one tends to start thinking that you really need a different title dynamic! As an aside, most film cameras use disk shutters so the exposure duration is the same for all areas of the frame, but of course the frame is progressively opened and progressively shut. Some cameras used an oscillating blade shutter, so in that instance there was a variation in exposure across the frame (usually less at the top -- the sky area). Not all had 180 deg shutters -- the Bolex was 165 deg. So now that useless information can be included in your modelling!

Serena
farss wrote on 11/8/2005, 3:13 AM
Thanks,
so when I build MY NLE with track motion I can have presets for shutter angle and camera type, actually I think I've seen something like that in some CGI application under the motion blur settings, hm.
I think what I was remembering about shutter design goes back to what a stills photographer was telling me about the different kinds of shutters they used, roller blind (what a thing they were) and iris etc.

Problem with changing the title dynamics is the client has already decided what he wants, well not really that precisely. More a mind exercise for me than anything else, sort of lots of bits of information coming together and now I remember some guy saying the problem with CGI is exactly this same issue, the motion blur doesn't match what a real camera records. But more than that, I've had some footage that was a simple camera tracked over a printed page and it always looks different to scanning the page and simulating the pan in Vegas, this isn't a film versus video thing, it's a real camera versus a virtual one.
Bob.