Increase shutter speed for 3D modeling

[CW3Drones]

Has anyone “solved” the issue of rolling shutter for 3D modeling?

I’m flying an Autel Evo II 8k and processing with Web ODM. I’m going to check out Measure Ground Control next, before I bite the bullet and knuckle under to Pix4D or Drone Deploy.

I’m wondering if I increase my shutter speed and slow my airspeed, whether my image captures will be clearer when processing for 3D?

Thoughts?

 

[herein2021]

Has anyone “solved” the issue of rolling shutter for 3D modeling?

I’m flying an Autel Evo II 8k and processing with Web ODM. I’m going to check out Measure Ground Control next, before I bite the bullet and knuckle under to Pix4D or Drone Deploy.

I’m wondering if I increase my shutter speed and slow my airspeed, whether my image captures will be clearer when processing for 3D?

Thoughts?

I know nothing about 3D modelling but I can tell you that as soon as your shutter speed exceeds double your framerate, there is nothing more that the shutter speed can do to reduce rolling shutter distortion; once you go beyond double the framerate all the shutter speed will do for you at that point is reduce motion blur. Rolling shutter effects/problems are due to rolling shutter sensor readout speeds which is a fixed value that cannot be changed once the camera is manufactured.

With drones you typically will not run into rolling shutter issues as long as your gimbal is steady and the drone does not pan too quickly. Drone sensors have very slow readout speeds probably to save costs and because due to the nature of drones they simply do not need faster readout speeds. If you pan quickly you will see some pretty bad rolling shutter. But for typical drone flights where you are flying slow and steady with that wide angle lens and drone to subject distance you shouldn't have any problems with rolling shutter.

So the tips that I would recommend to reduce rolling shutter distortion is:

• Shutter Speed - always keep it at 2x the framerate or higher. My own exception to this rule is when filming at night. At night I use a 30FPS framerate and a 1/30s shutter speed because I'd rather gain the stop of light vs increase the ISO and rolling shutter distortion just isn't something I worry about.
• Flight Speed - the slower you fly the steadier the drone and the steadier the drone the less "jello" you will see in your footage.
• Wind - fly when there is as little wind as possible, once again, the focus is on stability and not exceeding the gimbal's capabilities, calmer days are better than windy days for drone stability
• Drone to Subject Distance - The further you are from the ground/subject, the fewer effective pixels that will change from frame giving the perception of moving slower and the slower things seem to move the less rolling shutter distortion will be visible, so simply fly higher to reduce rolling shutter distortion. Or if the subject is a building, then fly farther away from it.

 

[CW3Drones]

I know nothing about 3D modelling but I can tell you that as soon as your shutter speed exceeds double your framerate, there is nothing more that the shutter speed can do to reduce rolling shutter distortion; once you go beyond double the framerate all the shutter speed will do for you at that point is reduce motion blur. Rolling shutter effects/problems are due to rolling shutter sensor readout speeds which is a fixed value that cannot be changed once the camera is manufactured.

With drones you typically will not run into rolling shutter issues as long as your gimbal is steady and the drone does not pan too quickly. Drone sensors have very slow readout speeds probably to save costs and because due to the nature of drones they simply do not need faster readout speeds. If you pan quickly you will see some pretty bad rolling shutter. But for typical drone flights where you are flying slow and steady with that wide angle lens and drone to subject distance you shouldn't have any problems with rolling shutter.

So the tips that I would recommend to reduce rolling shutter distortion is:

• Shutter Speed - always keep it at 2x the framerate or higher. My own exception to this rule is when filming at night. At night I use a 30FPS framerate and a 1/30s shutter speed because I'd rather gain the stop of light vs increase the ISO and rolling shutter distortion just isn't something I worry about.
• Flight Speed - the slower you fly the steadier the drone and the steadier the drone the less "jello" you will see in your footage.
• Wind - fly when there is as little wind as possible, once again, the focus is on stability and not exceeding the gimbal's capabilities, calmer days are better than windy days for drone stability
• Drone to Subject Distance - The further you are from the ground/subject, the fewer effective pixels that will change from frame giving the perception of moving slower and the slower things seem to move the less rolling shutter distortion will be visible, so simply fly higher to reduce rolling shutter distortion. Or if the subject is a building, then fly farther away from it.

Thanks for this. I hadn't considered the fact that distance + steadiness, could reduce the impact of rolling shutter defects. I'll give that a shot! I erroneously thought closer meant clearer, but now I can see my error. Looking through a microscope I'd need to move slower than when looking through a telescope!
~
Cheers!

 

[herein2021]

Thanks for this. I hadn't considered the fact that distance + steadiness, could reduce the impact of rolling shutter defects. I'll give that a shot! I erroneously thought closer meant clearer, but now I can see my error. Looking through a microscope I'd need to move slower than when looking through a telescope!
~
Cheers!

It will definitely help since the very definition of rolling shutter distortion is the inability of the sensor to capture all of the pixels in the scene at the same time since there is a delay when reading from the top to the bottom of the sensor. So, by flying father away, fewer pixels are changing from frame to frame giving the sensor more time to capture the entire scene.

Kind of like if you are standing on a curb and a car passes by at 60MPH it will seem very fast, but if you are up in the bleachers watching a car race a 60MPH car will seem very slow. With compressed video in particular, it is easy to overload the compression algorithm with too much fast motion at which point you will see macro blocking and artifacts, so slow and farther away definitely works best.

You are correct though, the farther away you are from the subject, the more details that will be lost, so it will be a balancing act finding the perfect subject to drone distance. For my work, rolling shutter distortion has never been a problem with modern drones; earlier ones had terrible problems due to the gimbals not being properly isolated from the drone's vibrations.

 

[mcq]

I use an EVO II 8k camera for mapping in WebODM. I know if I do a double grid the rolling shutter effect (bow in the 3-d models) goes away (see WebODM's "Creating High Quality Orthophotos"). I also think using ground control will remove the bow also.

 

[Detritalgeo]

Make sure you enable the rolling shutter "correction" in ODM. It's not perfect but worth evaluating. Works best if you know the exact speed of the readout.

 

[leving]

Does anyone know or has experimentally found the speed of readout for the 48MP sensor?