Video Cameras

[JohnM]

Frame rate is part of it but the wavy blades are caused by the scan rate of the digital cameras. Any image in the lens is being scanned and if the object is moving it will be scanned in a new location as the scan moves through all of the rows of pixels.

JM

[RanRan]

Frame rate is part of it but the wavy blades are caused by the scan rate of the digital cameras. Any image in the lens is being scanned and if the object is moving it will be scanned in a new location as the scan moves through all of the rows of pixels.

JM

You're thinking of interlaced video on CRT sets. If you are using an interlaced camera each frame is shot in two fields and then interlaced (put together). Most newer cameras are shooting progressive frames - there's only one 'field.' 60 frames interlaced equals 30 frames progressive. In either case the frames are not 'scanned' but processed as digits onto the tape or other media.

The wavy blades are caused by the electronic shutter speed and direction - on pro cameras you can change both. It's a little like the very early shots of moving race cars - where the wheels are distorted into ovals - they didn't have fast enough shutters on cameras back then to 'stop' the action.

[JohnM]

You're thinking of interlaced video on CRT sets. If you are using an interlaced camera each frame is shot in two fields and then interlaced (put together). Most newer cameras are shooting progressive frames - there's only one 'field.' 60 frames interlaced equals 30 frames progressive. In either case the frames are not 'scanned' but processed as digits onto the tape or other media.

Nope, I know about those. I was just relating what I had read in a technical journal about the same problem. ;-)

JM

[pilotmike]

I think JohnM is talking about the rolling shutters that some CMOS cameras have. I'd have to see single frames to tell if we were hitting that. Its at least possible. I doubt its the whole problem though. The pro cameras use CCDs with global shutters so they'd never see anything like that.

And just to make sure that we are all completely confused... the "GOPro" cameras are not pro... they are CMOS (which doesn't mean that they aren't lots of fun and plenty good for lots of applications).

Any chance that turbopilot just has a really broken and twisted prop that occasionally runs backward just like it looks in the video

[RanRan]

Nope, I know about those. I was just relating what I had read in a technical journal about the same problem. ;-)

JM

John, that technical journal is wrong - there is no such thing as a 'scan rate' in camera specs.

And Mike, you've done your homework, but a rolling shutter effect has to do with camera movement (in certain cameras) not recording the action in front of it. The best professional cameras today are using CMOS sensors.

[pilotmike]

The latest version of the AOPA magazine has an advertisement for a camera that claims to improve this problem. I think it's "NFLIGHTCAM+" but I don't have it here so I'm not positive.

I looked on their website and they don't make any claims there... BUT they do have a video from the cockpit of a military jet and sure enough... no funny prop stuff

[RanRan]

The latest version of the AOPA magazine has an advertisement for a camera that claims to improve this problem. I think it's "NFLIGHTCAM+" but I don't have it here so I'm not positive.

I looked on their website and they don't make any claims there... BUT they do have a video from the cockpit of a military jet and sure enough... no funny prop stuff

They had a short clip on the home page video - that showed a clear shot through the blurred prop. Whatever. But I suspect their marketing in general - 'the camera has an aviation lens' - what the heck is THAT??

All these little 1/4" - 1/5" sensor cameras are very limited in what they can do - even Sony's $3000 model.

Since these cameras don't have an iris, they have to manipulate exposure via electronic shutter speed and processing. I would guess they got the blurred prop shot by using their bizarre rate of 720P @ 60P frames per second - that would force the shutter speed down but, probably, would only work in a tight range of high prop rpms and lighting conditions.

That said, it looks like it would be easy to mount to a strut, and the gps tie-in is pretty cool...not to mention a genuine aviation lens.

[pilotmike]

nflightcam.jpg

Here's the advertisement I saw. Just to be clear - I'm not endorsing this product. I've never tried it before and I have nothing to do with the company.

RanRan - everyone knows that an "aviation lens" is just the same as all the other lenses but costs 5x more