Moving LED Flares!?

[Soulhunter]

Someone knows whats causing this strange effect (http://www.sendspace.com/file/zt7uhx) when filming LEDs with my digicam?


Tia n' Bye

[wonkey_monkey]

I'm not sure of the details, but I think it's something to do with the way CCDs work - each pixel of the sensor stores up a charge which is then "drained" out through the rest of the pixels in that row, but the LEDs are so bright that the image is persisting (I wouldn't be surprised if the lines move by exactly one pixel per frame). I've seen a similar effect on an SLR camera, where if you take a photo of an extremely bright source, the brightest points will smear in a vertical line because of this effect.

David

[Soulhunter]

Btw, I only get this effect on the cams LCD or when I make videos, not when I take pictures... Also, I dont get this effect when filming the standby LEDs of my TV/Amp/PC etc, seems it just works with the ones i filmed in this video... Its the first time I see something like this, also never heard of this phenomenon!

[JohnnyMalaria]

Can you post a still frame from that video? 14MB is too much for my s-l-o-w-p-o-k-e connection :)

Without seeing it, I expect you are seeing vertical bands - is that right? Typically, this phenomenon is worse at faster shutter speeds when you are trying to shoot very bright objects in dark surroundings.

You can see an example here (once the sun rises):

http://www.enosoft.net/video/Zanzibar%20Sunrise%202.wmv

(Originally recorded with a PAL Video 8 analog camcorder.)

Aslo see http://en.wikipedia.org/wiki/Frame_transfer_CCD .

[Soulhunter]

Sure, here are two stills...

http://img66.imageshack.us/img66/2063/01qt8.th.jpg (http://img66.imageshack.us/my.php?image=01qt8.jpg) http://img116.imageshack.us/img116/4471/02gb7.th.jpg (http://img116.imageshack.us/my.php?image=02gb7.jpg)


Tia n Bye

[FredThompson]

Highly saturated, high contrast source and a restricted luma range for the light does this. You'll see other problems with DV and industrial lighting, almost-parallel lines, etc.

FWIW, it's impossible to have a one-pixel-side color in DV. Look at the sample images from the development of 411Helper for VirtualDub and you'll see other chroma weirdness.

DV is pretty good for "natural" subjects but really breaks down quickly in some settings, like your super-bright LEDs in darkness.

[Soulhunter]

Alternative link to the video! (http://video.google.de/videoplay?docid=7512341248529812100&hl)

Tia n' Bye

[JohnnyMalaria]

You're seeing the vertical smearing as described earlier. The reason that the the smears seem broken is because your LEDs are strobing (i.e., not continuous - most likely being driven from an AC source).

It's nothing to do with the DV codec. It's to do with the fundamental design of the CCD sensor.

I've seen similar behavior with analog Video 8 camcorder recordings.