Prop Lines On Video (Full Version)

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n00bflyer -> Prop Lines On Video (4/21/2008 12:11:43 AM)

Is there any way to reduce or remove the horizontal lines that appear when the prop is spinning in front of the camera? I have a 380 TV lines e-bay camera that I'm otherwise happy with but the lines are driving me nuts. I have tried an orange prop....BAD a black prob, OK, maybe I should try a grey prop or a light blue prop to blend in with the sky. Any other recommendations? I want to start flying FPV style soon and I'd like to fix this problem before I do. Thanks =)



Quacker -> RE: Prop Lines On Video (4/21/2008 4:45:14 AM)

Hi nOOb,

Those lines are typical of any CMOS camera. A different prop color might fool you in some lighting conditions, but for the most part, it is what it is. Only getting the camera out from behind the prop is a solution other than replacing it with a CCD camera.

Regards,
Q



n00bflyer -> RE: Prop Lines On Video (4/21/2008 5:24:13 AM)

Ahh, darn. You don't happen to have a used CCD camera you might want to sell? =)



moogly -> RE: Prop Lines On Video (4/21/2008 12:45:57 PM)

the Only way to get rid of them is moving the camera way from the prop.
Any camera will see the pro due to shutter speed. Its like trying to point you camcorder at a TV and you get the same thing you see the sync lines and theres no way around it unless you could sync the shutter speed to the prop speed



Quacker -> RE: Prop Lines On Video (4/21/2008 3:50:15 PM)

While any camera will 'see' the prop, I believe that his concern is with the apparent swirling lines that are a function of the way the CMOS camera processes the image. By contrast, a CCD camera will actually display the prop in a strobe-like manner when the RPM's are an even division of the camera field rate. The rest of the time, it will appear as a dimly visible disk that is so familiar from film.



moogly -> RE: Prop Lines On Video (4/21/2008 5:33:33 PM)

Well I have both a ccd and a cmos and both show the prop as lines so I beleive it due function of the to the shutter speed and not the pick up (CCD or CMOS) just my opion and experience[:D]
if you look a www.putfile.com/mbren and look @ the hopkins high vid that was shot with a CCD
Or try thi link http://www.rcuvideos.com/item/PCRFCTHZ6WGHMZLH the video sucks[:o] but you can see the prop on the left that was shot with a cmos good luck[&:]



Quacker -> RE: Prop Lines On Video (4/21/2008 6:02:10 PM)

your 2 videos are distinctly different. In the first, using a CCD camera, you can observe the image of the propeller strobing. In the second, using a CMOS camera, you are seeing successive slices of the prop as the CMOS element is scanned. Note that in the 2nd video, the lines are all horizontal, not radial as a propeller actually is. If you were to pan back and get a bigger slice of the arc, you would see that the stripes would be pervasive can be quite annoying to some people.



hpux735 -> RE: Prop Lines On Video (4/23/2008 6:40:44 AM)

So, what you're saying is that a CMOS pixel only collects photons only during the moment that it is being scanned?

I know that CCD's build-up a charge (like a capacitor) during the duration 1/(shutter speed). I am not aware of
any shutter in the small "board" cameras that are typical of this kind of work, and that implies that the CCD is not
able (by my reasoning) to have an entire frame coherent in time. I think this because while there may be some
way to prevent building up a charge at the beginning of the frame, I can't think of a way to prevent further
accumulation once the desired time has elapsed, is there something I'm missing? Also, with a CMOS
element, if it a pixel is only collecting photons while it's active, then how do you not get hopelessly dark images?

Thanks



Quacker -> RE: Prop Lines On Video (4/23/2008 2:57:45 PM)

A CCD electronically shutters the imaging element at a single moment in time, thus the spinning propeller may appear strobed when the prop speed and shutter repetition rate near an even division. Low cost CMOS cameras use a "rolling (electronic) shutter" and this accounts for the stripes that are observed from a spinning propeller. The reason for the rolling shutter is that it allows for a lower number of transistors adjacent to each sensitive pixel area and thus lowers cost and complexity while increasing the available sensitive area for better performance.



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