BMPC4K and post stabilization

Hello folks!

For a barely no budget music video , I need a 5minutes shot of a walk in the woods just landscape , no actors.
The Idea is to mimic a steadycam shot with a shoulder mounted camera.

As the budget is close to nothing, I was looking for cheap solution and came to the idea that the most affordable way to do would be to rent the BMPC4K (I already have all accessories from my BMCC) , for it's global shutter and resolution(we deliver in 1920X1080.

So i have a few question about post stabilization as I barely used it before:

*I assume that I have to increase the shutter speed: motion blur could fill unnatural as the shaking will be compensated. Probably better to had some in post if needed. Am I assuming wrong?

*If I'm right , what angle value gave you the best results from your experience?

*Just to calculate an approximate focal value, what is your approximative average % of crop when using post stabilization on a normal speed walk, shoulder mounted?



I know that it is not ideal , but the steadycam or gimbal are out of our price range.
My apologies if it has already been discussed here, I was not able to find it.

Thank you!

Personally I would be tempted to use a cinema camera at 2.5k so you don't crop as much. Use a monopod with some weight attached to the bottom to stabilise the camera - I always find this far more stable than a shoulder mount and should keep the camera "on axis" enough to keep the post stabilised crop to a minimum.

In terms of focal length I would use the ratio of acquisition to output resolution as your guide - i.e. HD is 80% of 2.5k so a 24mm becomes approx. 19mm. HD is 50% of UHD so 24mm becomes 12mm.

Personally I would be tempted to use a cinema camera at 2.5k so you don't crop as much. Use a monopod with some weight attached to the bottom to stabilise the camera - I always find this far more stable than a shoulder mount and should keep the camera "on axis" enough to keep the post stabilised crop to a minimum.

In terms of focal length I would use the ratio of acquisition to output resolution as your guide - i.e. HD is 80% of 2.5k so a 24mm becomes approx. 19mm. HD is 50% of UHD so 24mm becomes 12mm.

Thanks.

I doubt i will be that stable after 5 full minutes of walking with Camera lens batteries + weight , especially after the rehearsal.
My Idea with the 4K was to take advantage of the global shutter , and just crop what I need to stabilize , and then downscale to 1920X1080.

Adrien, without knowing what lens you plan on using, one cannot give you an answer confidently. You should use a fairly wide angle lens when walking if that suits your video. If you shoot raw on the BMPC4K, you probably have more than enough area to get a satisfactory result using stabilization in post for a 1920x1080 video. The wider the lens, the frame will have less motion; a long lens on your shoulder will be harder to get good looking results unless you want to shoot Blair Witch.

Since no actors are involved, it should be easy for you to walk that five minutes and experiment with a few different shutter angles. You may find the 180 degrees is fine and 90 degrees will give you an unnatural motion. Something in between those values should also work.


Rick Lang
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Adrien, without knowing what lens you plan on using, one cannot give you an answer confidently. You should use a fairly wide angle lens when walking if that suits your video. If you shoot raw on the BMPC4K, you probably have more than enough area to get a satisfactory result using stabilization in post for a 1920x1080 video. The wider the lens, the frame will have less motion; a long lens on your shoulder will be harder to get good looking results unless you want to shoot Blair Witch.

Since no actors are involved, it should be easy for you to walk that five minutes and experiment with a few different shutter angles. You may find the 180 degrees is fine and 90 degrees will give you an unnatural motion. Something in between those values should also work.


Rick Lang
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Yes , indeed I forgot to precise what lens I would like to emulate , since I would probably have shot it with a stead at 18mm or 24mm , I will just grab a Tokina 11-16 and improvise around it. As I deliver in 1080, It will still let me choice in post, and i remember that the distortion was really acceptable for the focal value last time I used it.
I found a drone shot without gimbal, stabilized in post , at 180° , and all my fears about any unatural motion blur vanished, .
Thanks to you two for your quick answer. If I have time during this shooting day , I will still experiment with shutter angle and longer focal and post my results.
I wish you a Happy new year and lots of passionate hard work!!!

The Idea is to mimic a steadycam shot with a shoulder mounted camera

Are you trying to shoot one long continuous shot? Because I can tell you right now you will simply not achieve a "steadycam look" for one long shoulder mounted take. No matter how good the stabilization software is it will never be able to correct a long take in as complex an environment as a forest. Forests have a LOT of parallax. Parallax makes life hard for stabilization software and often cause errors in scaling and perspective warping. Post stabilization works best for shorter clips, and with less complex scene geography.

Why don't you look at a DIY steadycam of some kind? You can make one from essentially pvc, some counterweights, and a little ingenuity. It won't be perfect, but WAY better than handheld. Google it, I'm sure you can find something.

I would strongly recommend testing with different shutter speeds before you go out on location. I've done a number of shoots from planes with the BMPC, and while I can remove the translation from the frame, the motion blur at 180 effectively ruins the shot.

I would strongly recommend testing with different shutter speeds before you go out on location. I've done a number of shoots from planes with the BMPC, and while I can remove the translation from the frame, the motion blur at 180 effectively ruins the shot.

+1

Best practice for this is to shoot with a shutter fast enough to eliminate all motion blur, stabilize, then process the final shot with an optical flow-field motion blur like ReelSmart Motion Blur set to 180º.

The initial resolution won't mater because no matter how much you crop, the shot will never be able to be stabilised in post.

A constantly tracking single shot where what's in front is always changing won't be able to be stabilised because there's nothing to track to.

I'd get a small gimbal instead and use a pocket with a wide lens and a deep stop. If you're placing all your eggs in one basket by only having a single shot you need it to work or else what's the point.

JB

Couldn't you ask someone with a drone?
With a Phantom II and a GoPro in a gimbal you got very stabile videos, even in 4k.
When you have good lightconditions the footage will be very well.

John, granted if you are walking through the woods for five minutes, there is no content from the opening frame that would be in a frame a few seconds later so stabilization isn't going to work in that sense. My thinking was that the little bumps and waver of the camera from frame to frame would be smoothed somewhat. The only time I've done post stabilization was a much shorter handheld pan along a small stream of flowing water; the beginning and ending frames were quite different, but the slow handheld pan was smoother from the stabilization as the frame was cropped by the stabilization to 'centre' on the stabilized content.

When he said, no actors were involved, I assumed first person POV. I didn't think the Adrien was expecting anything like a rock solid track from a long walk in the woods as that likely wouldn't even feel right in the film, if the walk is intended to be a first person point of view shot, but is trying to smooth out the bumps. If he needs that long walk to look very smooth as in a third person POV (as we see the walk through the eye of the camera), then you're absolutely right.


Rick Lang
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Thanks for all the warning.

As I stated , I have no experience with huge post-stabilization. My plan was to shot it "post-stabilization" friendly: walking in straight line and stop walking when (slowly) panning /turning into a direction(location is perfect for that) : i naively assumed that, as long as a software have at least 3 point of tracking(such as on rocks or tree trunks) between 2 frame for the whole shot and as long as I set some key frame, I'll be fine.

I suppose too much time spent in studio can makes you forget the complexity of real world .

The steadiecam or gimbal stabilizer option are way too expensive for now but I'll do what I always did facing this situation : work with my friend/director to find a viable compromise(already did but he is kind of stubborn , so i need to try harder ) or get the funding to make it right.

Thanks for sharing your experience with me.