Best settings for a simple match-move project

Mark Johnson

Mark Johnson

The Dude Abides
I'm going to shoot some freeway footage with my HVX mounted on the windshield using a suction mount rig. I've shot with this before and it works out nicely. However, I have a project that will require match-moving the footage to add CG vehicles for a forensic case. I'm not concerned about "film look" and simply want to get the best footage to derive a solid match using matchmover pro. I want to minimize motion blur so that features can be locked as close to the camera as possible so I assume that I need to use as small a shutter speed as possible. Would it be better to shoot 60 frames interlaced or go to a lower frame rate but with full-res progressive frames? Any help or suggestions would be appreciated.

Mark Johnson
www.forensicarts.com
 
Mark,

I would definitely suggest shooting progressive rather than interlaced. Beyond that I would consider shooting natively at 30p, especially if your presentation might benefit from overcranking the footage into smooth slow motion (shooting at 60fps and placing it in a 30p or 29.97 project)

I would recommend setting the shutter between 60 and 125 and not going with a much higher number (faster shutter speed) than is neccesary to avoid too much motion blur. Keep in mind that your shutter speed being raised up will require the aperture of the lens to be opened up to let more light in.

One priority that you might consider for getting the best quality out of the lens is to use a neutral density filter setting in combination with the shutter setting to get your aperture in the low-mid to mid range aperture settings like f/4 or f/6 because this range is typically where the lens will provide the best image quality through the glass. As long as your shutter speed is more than double your frame rate you should not have too much of an issue with motion blur unless you are moving the camera itself very quickly.

On the other hand if the shot is going to have vehicles rushing through the field of view fairly quickly and from a relatively close point of view, then you are definitely going to need to raise the shutter speed considerably higher.

It sounds like the work you do must be truly fascinating. Do you ever need work done out in Ohio? Me thinks forensic work would be very satisfying work indeed! :)
 
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Thanks for those suggestions. Very good ones indeed. I'm going to try to shoot with as little oncoming traffic as possible, given that such movement would make the match more difficult and would probably require masking out those vehicles. The roadway I'm shooting has a lot of pavement cracks and material changes that will be good for getting feature matches on, but as they get close to the camera their relative motion will be fast (70mph). Thus, since it's mid-afternoon daylight I should be able to raise the shutter to minimize the blur of the pavement. Good point about using the neutral density filters. I have just been reading Barry's new book and have appreciated his comments about lens performance and optimum aperture settings.

Yes, I do occasionally have work out your way and I'd be happy to seek your assistance the next time. I've had a bunch of stuff near Columbus and also had the pleasure of downing a lot of beer on Mt. Adams when I was working near Cincy.

My niche is a small one but has been very good to me. I was a trial lawyer for 14 years so I know the field from that side of the table and can deal with the foundation/evidentiary issues with some credibility (more credibility than I have behind the camera, but I'm working on that :)

Mark
 
I wouldn't do anything special with the shutter for your vfx shots. It's going to make you question the shot when it's finished. Why is the shot of the ambulance so 'juddery'? You'll need to render your cg with the same shuttter as your camera and a bunch of sharp frames will look terrible in that context. The motion blur will help hide the errors in the matchmove.
180 degree shuttter.
15 years in vfx and 5 at ilm. Believe me.
Cheers,
Sam
 
I'm just finishing match moving 30 or so shots of skydivers, planes on the runway, etc. all with HVX material, so I'm pretty sensitive to less than optimal tracks. Some suggestions for your particular situation...

-30fps progressive, or try an experiment using 60p and then making 30i (29.97 interlaced) out of it in post after the work is done... this will give you 60 frames per second of good full-rez progressive to double your temporal resolution.

-For gosh sake turn off the OIS system. No auto iris/focus and don't zoom.

-Most important... I figure out the lens distortion at the particular focal length and "undistort" the images before tracking. Then I re-distort if necessary after adding CGI. Doing this I've worked well with the HVX at full wide and also the Century .6 adaptor.

20 years in vfx and I once knew a once guy who worked at ILM. Believe me. :)

Jim Arthurs
 
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