Rolling shutter Jello

[Don]

The complicating factors here are multiplying quickly.

1. ND filters. These appear to be a lot more practical with the GoPro than with the Drift because of the physical geometry of the cameras. I'll play with shutter speeds and 1080p vs 720p first.

2. It seemed to me that using a ND filter primarily got rid of whacky prop images by slowing down the shutter speed. I think Glen essentially said as much - ND filters and increasing shutter speed are at cross purposes.

3. Vibration wasn't something I'd given thought to. I may buy some longer screws from ACS and try some different foams to reduce vibration.

4. The notion that vibrations are mostly cause by the engine seems a bit simple - I'd think the prop would contribute (a) vibration(s) and hence we balance them. I would also think the airframe may have some intrinsic vibration that isn't normally an issue until its exacerbated (flutter) or maybe interferes with low end videography. FWIW, flying commercially I have frequently watched wings oscillate. I'd guess not every vibration that might affect video results is visible.

In the end it looks like I can experiment with:
-engine speed (and when 702DA is finished, engine and prop speeds)
-vibration isolation
-shutter speeds (fps)
-scan rates (720p vs 1080p)

Thanks for the thought gentlemen and if I get any results worth reporting, I'll let you know.

[humptybump]

Don - While there are lots of things vibrating on an airplane - engine vs prop vs other things - those can all be normalized to RPM.

In case someone wants to see a VIVID example of the phenomenon, here is a short video I shot a while back ...

http://vimeo.com/31002944

Jump to 2:10 and watch what happens when I change RPMs at 2:14 and then again at 2:22

[Don]

Interesting Glen - that's worse than what I was dealing with but that is what I'm talking about.

I'll start out testing engine RPMs and see what my results are.

Do you have any opinion if you could effectively isolate the camera from vibrations without a lot of expense?

[humptybump]

Don - I shared that clip because it is an ideal (and extreme case). I have a small bit of padding and it has no effect. Given I can map it to RPM, I just plan to map the effect to a range of my RPM settings. That way, I can know when I'll have unusable video.

[Sam Buchanan]

Based on my experience with a Drift camera on my Legal Eagle XL (LOTS of airframe vibration!), I think we are getting "shutter speed" and "frame rate" confused. The two terms are not referring to the same camera mechanics.

I have my Drift camera set to 60 fps because it reduces shutter roll (jello) effects. But the camera shutter speed can vary while still operating at 60 fps. Here are real-world examples:

http://www.youtube.com/watch?v=f9iforGIIQ0

This vid was shot in bright daylight at 60 fps. Notice the prop artifacts caused by the scanning of the shutter.

Here is a video shot in low evening light at 60 fps, notice how the prop is now blurring instead of "chopping":

http://www.youtube.com/watch?v=ndSqKW94WCQ

The reason the prop blur is enhanced in low light is because the camera decreased shutter speed in order to achieve proper exposure. The frame rate was 60 fps in both cases, it didn't change, but shutter speed did change.

Density filters have been recommended in order to increase prop blur by slowing the shutter speed. But high frame rate is the best method for reducing rolling due to airframe vibration. Using a neutral density filter will not impact frame rate, that is a setting in the camera menu.

Hope this helps,

[Don]

Originally Posted by Sam Buchanan

Based on my experience with a Drift camera on my Legal Eagle XL (LOTS of airframe vibration!), I think we are getting "shutter speed" and "frame rate" confused. The two terms are not referring to the same camera mechanics.

Hope this helps,

Sam,

You're right I was using the terms interchangeably...I think. Thanks for picking up on this and trying to straighten me out. Something was bugging me from my SLR and film days but I had not put my finger on it. Let see if I understand the difference.

When I set the frame rate to 60 FPS, the I will always get 60 FPS regardless of the lighting. What the camera will change (in order to get the right exposure) is the "shutter speed." I'm further guessing that the shutter speed is really the speed that the progressive scan that makes up one frame is completed. I'm going to stick my neck out and say it sounds to me like, if you're shooting at 60 frames per second, the scan rate (or shutter speed) had to be 1/60th of a second (and maybe a bit faster to make up for lag) or faster. If the light was bright the scan rate (i.e., shutter speed) could go up several or many times the previous 1/60th of a second rate.

In bright light, I can imagine the scan rate may be 1/1000 sec or faster to get the right exposure but, the frame rate will still be 60 FPS. In dim light the scan rate (or shutter speed) would drop to 1/60 sec (or a bit faster) and fast moving stuff would be blurred.

Do I have the difference between frame rate and shutter speed correct?

[humptybump]

Sam, yes. I was not clarifying very well.

Don, yes. In theory the shutter rate could only go as low as the frame rate since it would need to start a subsequent frame as soon as it finished the current one. At any faster shutter rate, the camera would simply wait until it was time to start the next frame.

I have som ND film (from the old theater days). I'll see if I can install it "behind" the lens of the Drift. It may help in certain cases but not all. It may bugger the whole thing up so no one try this at home.

[Low Pass]

Originally Posted by Sam Buchanan

Based on my experience with a Drift camera on my Legal Eagle XL (LOTS of airframe vibration!), I think we are getting "shutter speed" and "frame rate" confused. The two terms are not referring to the same camera mechanics.

I have my Drift camera set to 60 fps because it reduces shutter roll (jello) effects. But the camera shutter speed can vary while still operating at 60 fps. Here are real-world examples:

http://www.youtube.com/watch?v=f9iforGIIQ0

This vid was shot in bright daylight at 60 fps. Notice the prop artifacts caused by the scanning of the shutter.

Here is a video shot in low evening light at 60 fps, notice how the prop is now blurring instead of "chopping":

http://www.youtube.com/watch?v=ndSqKW94WCQ

The reason the prop blur is enhanced in low light is because the camera decreased shutter speed in order to achieve proper exposure. The frame rate was 60 fps in both cases, it didn't change, but shutter speed did change.

Density filters have been recommended in order to increase prop blur by slowing the shutter speed. But high frame rate is the best method for reducing rolling due to airframe vibration. Using a neutral density filter will not impact frame rate, that is a setting in the camera menu.

Hope this helps,

Good information, and great videos! Thanks!!!

[Sam Buchanan]

Originally Posted by Don

Sam,

You're right I was using the terms interchangeably...I think. Thanks for picking up on this and trying to straighten me out. Something was bugging me from my SLR and film days but I had not put my finger on it. Let see if I understand the difference.

When I set the frame rate to 60 FPS, the I will always get 60 FPS regardless of the lighting. What the camera will change (in order to get the right exposure) is the "shutter speed." I'm further guessing that the shutter speed is really the speed that the progressive scan that makes up one frame is completed. I'm going to stick my neck out and say it sounds to me like, if you're shooting at 60 frames per second, the scan rate (or shutter speed) had to be 1/60th of a second (and maybe a bit faster to make up for lag) or faster. If the light was bright the scan rate (i.e., shutter speed) could go up several or many times the previous 1/60th of a second rate.

In bright light, I can imagine the scan rate may be 1/1000 sec or faster to get the right exposure but, the frame rate will still be 60 FPS. In dim light the scan rate (or shutter speed) would drop to 1/60 sec (or a bit faster) and fast moving stuff would be blurred.

Do I have the difference between frame rate and shutter speed correct?

No, I can't see frame rate exceeding 60 fps. The software we use to produce videos is designed (per menu selection) for a specific frame rate (30 fps, 60 fps, etc).

I think the frame rate is locked per the setting in the camera menu. But shutter speed can vary and still not impact frame rate--a high shutter speed will just mean a particular scan line was exposed for a briefer period of time than a scan line with a slower shutter speed.

Shutter speed and frame rate are not related (except maybe on the slow end) if my understanding of camera mechanics is correct (but still willing to learn after 32 years in the photography biz...).

[Don]

Originally Posted by Sam Buchanan

No, I can't see frame rate exceeding 60 fps. The software we use to produce videos is designed (per menu selection) for a specific frame rate (30 fps, 60 fps, etc).

I think the frame rate is locked per the setting in the camera menu. But shutter speed can vary and still not impact frame rate--a high shutter speed will just mean a particular scan line was exposed for a briefer period of time than a scan line with a slower shutter speed.

Shutter speed and frame rate are not related (except maybe on the slow end) if my understanding of camera mechanics is correct (but still willing to learn after 32 years in the photography biz...).

I think we're meaning the same thing now with the terms frame rate and shutter speed/scan speed. FWIW, the Drift Ghost S will do 60 FPS @1080p, 120 FPS @720p and 240 FPS @WVGA. Not to debate you, but it doesn't seem like 60 FPS is a limit these days. What I don't know is if that's a spec to sell cameras or if that's something valuable to have.

Thanks for helping me get the concepts straight. It will be helpful as I explore what the camera can do.