Rolling shutter Jello

[Sam Buchanan]

Originally Posted by Don

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.

Yep, I need to read up on this some more. The high frame rate is due to the lower res image, not as many scans needed for one frame, not as a mechanism to determine exposure.

But I don't know how our production software handles the different rates. When outputting a finished video, we specify what frame rate we want. What happens between camera file and finished file I know not.

[humptybump]

For flying, I haven't see the 120fps will be as useful. It was motivated by the target audience for these POV cameras - the extreme sports community. You can imagine the "cool" factor of slowing down snowboarder in powder.

The latest iPhone also supports 120fps. I use it often for the slow-motion effect. (video examples of slow-motion)

I have not found a use for slow-motion while flying but I've not testing 120fps as a mechanism for reducing jelly roll.

There are a few more DIY options for added a neutral density filter to the GoPros. For the Drift cameras the best option will probably be to add an ND filter to a water proof housing.

-or-

[Sam Buchanan]

As another data point, I've noticed how the late evening Legal Eagle vids shot in really low light are softer than those shot with brighter light. This is no doubt due to the slow shutter speed needed to achieve proper exposure and airframe vibs that usually go unnoticed being apparent at the slow shutter speed.

So I assume the very high frame rates some cameras boast will be useful only with high light levels.

Another observation--as far as I know, YouTube dials the frame rate back to their default setting regardless of the quality of the uploaded file.

[Don]

Glen, the idea of adding the ND filter to a case makes a lot of sense to me. As for the higher frame rates, I wonder if there wouldn't be specific instances when you're trying to slow something down (not just general flying) that it would be handy.

For example, sometimes I have the nose-wheel shimmy but it isn't usual. So far, the only consistent variable seems to be whether I have a PAX or not. There are also two different motions I've seen. One is the side to side wobble (with a PAX) and the other is more of a bouncing oscillation that I've seen taking off solo on a paved runway. I wonder if descent slo-mo might help me sort out whether there's a problem with my technique or something else. I'm not trying to get off topic and discuss nose wheel shimmy, just saying there might be a use for slo-mo for other than dramatic effects.

[Canadian_JOY]

Question here from a complete videography idiot... Does the new Garmin camera use this same type of image sensor? Is it as likely to experience this same type of jello/warping/whatever image distortion?

At some point I'll buy a camera with the express intent of using it to capture first engine runs, first flights and who-knows-what further down the line. I'd rather fork out money for something that's going to produce a decent image in our little niche aviation application, so all advice is gratefully received.

[Don]

Originally Posted by Canadian_JOY

Question here from a complete videography idiot... Does the new Garmin camera use this same type of image sensor? Is it as likely to experience this same type of jello/warping/whatever image distortion?

I'm no expert but the Garmin VIRB uses a CMOS sensor. The choice in video cameras seems to be between a CMOS sensor, with a rolling shutter and a CCD sensor with a global shutter. They both have their strengths and weaknesses. Both are capable of producing high quality digital movies.

Until recently, CCD were high priced and produced the best quality images. Apparently, in recent times CMOS sensors are catching up on quality and CCD's are dropping in price.

From what I've seen from cameras in this class - mainly Drift and GoPro cameras, the quality can be amazing. If you learn about your camera, I think Glen has pretty well shown that the jello shimmy can be avoided and Sam and others have shown how to avoid whacky looking propellers while using a camera with a CMOS sensor. Apparently CCD sensors have an issue with "smearing" and I don't know what causes it or how to avoid it.

My best guess, armed with the little knowledge I have so far is, exploring the strengths and limits of your equipment, so you can play off the strengths and avoid the weaknesses, is worth more than just buying a camera with different limitations.

You might see if you can borrow a camera (Drift, GoPro, or VIRB) and simulate an engine start of first flight and see what 'artifacts' you find in your video and then try and avoid the problem. My guess is on engine start, your prop is going to look strange unless you shoot it with a ND filter or do it in low light. If you shoot the first flight from the ground, I don't think you'll have many issues...but likely it will be time well spent testing it out.

[Sam Buchanan]

Originally Posted by Canadian_JOY

Question here from a complete videography idiot... Does the new Garmin camera use this same type of image sensor? Is it as likely to experience this same type of jello/warping/whatever image distortion?

At some point I'll buy a camera with the express intent of using it to capture first engine runs, first flights and who-knows-what further down the line. I'd rather fork out money for something that's going to produce a decent image in our little niche aviation application, so all advice is gratefully received.

The jello/warping can be eliminated with a very rigid mount that is secured to something that doesn't vibrate. Unfortunately, most of the RAM mounts that have the camera cantilevered at the end of a ball-mounted arm will enhance vibrations as the camera jiggles at the end of the arm. Compound the problem with a rubber suction cup attachment and you really have a mess.

I tried several custom-built mounts on my Legal Eagle before finding one that really works nicely with insignificant vibration. Here is a sophisticated looking mount but I never could damp all the vibration from the two-cylinder VW engine:



The present mount has the camera mounted rigidly to the airframe without hanging on an arm:



This one works great.



These mounts are different from what you need on an RV but you get the idea. Fortunately, an RV doesn't have the large amplitude vibs of my little plane so we may have greater latitude in designing a mount.

[Low Pass]

Sam, you build or buy the Legal Eagle?

[Sam Buchanan]

Originally Posted by Low Pass

Sam, you build or buy the Legal Eagle?

Built it:

http://eaglexl-58.com

And the EAA webinar detailing its construction:

http://www.eaavideo.org/video.aspx?v=2634527737001

Fun little plane.

[Low Pass]

Originally Posted by Sam Buchanan

Built it:

http://eaglexl-58.com

And the EAA webinar detailing its construction:

http://www.eaavideo.org/video.aspx?v=2634527737001

Fun little plane.

All excellent info! Thanks !!!