11 replies to this topic

[David]

A question for the technical brains amongst you- what is happening here? I fired a fountain that burnt with a flare effect, and when I watched the video back there is an obvious green line, like a laser pointer, coming up from the firework. I didn't see it with the naked eye.

Just curious really, whats causes that? The camera is obviously picking up something sent off by the firework.


Here is the vid- Volcano with green flare

[Arthur Brown]

Sadly almost certainly either lens flare or an artifact from the ccd chip or a combination of both.

[T-sec]

Correct, a disatvantage of CCD chip based camera's. When shooting in direct light you will get the so called Smearing Effect.

Try it outside when dark and shoot directly a streetlantern, you will get the same effect.

[marble]

Yep, its a artifact

[MDH]

It's a camera artifact.

What I'm more concerned about is the fact that you payed money for that fountain.

[T-sec]

LOL, what ever.

Next cam, buy a CMOS chip based one. Problems will be over.

[David]

Next cam, buy a CMOS chip based one. Problems will be over.

Camera was a gift!

Edited by David, 31 December 2007 - 02:14 AM.

[marble]

CMOS suck

[will-TM]

Having no camera is even worse

Edited by will-TM, 31 December 2007 - 07:27 AM.

[Anders Greenman]

Nope! Hi8 with no way to transfer the data to your pc is even worse!
I bought NTSC instead of PAL making it impossible without analog-digital converters..

Edited by Anders Greenman, 31 December 2007 - 10:05 AM.

[Andrew]

Having no camera is even worse

LOL

CCD and CMOS technologies both have these problems. CCDs get lines on the vertical and horizontal because of residual charge left in the array and output buffer. CMOS technologies suffer from charge spill over too, resulting in the perception of Mie scattering (commonly called glare).

In this case only vertical excitation of the green filtered CCD has occurred. If you look carefully you can see the green line below the fountain as well! Given only the vertical excitation has occurred I'd be inclined to suggest that it is an artefact caused by the lens or filters, not the active semiconductors. Try this, look at a light, whether it be a bulb or street lamp, it looks clear. Then close your eyes so that you can only just see through. You get a similar effect. This is a combination of diffraction caused by the eye lashes and stopped gap of the lids, and from distorting the position and shape of the lens in the eye. It has nothing to do with the back of the eye. Back to the video, this single vertical line is probably caused by a uniform imperfection in the lens/filter (most likely the green filter) that is about 550nm across. Also possible is that the imperfection is the result of fringing patterns. I'd maybe even put money on it being the green filter! The reason I say that is because some dyes (especially those that rely on colour centres) tend to line up coherently, causing coherent diffraction patterns orthogonal to the arrangement of the dye.

What you need to get is a camera that has an imaging chip with anti-blooming technology. This acts to prevent excess charge migrating to other active sites. More importantly, you need good optics; poor quality optics and filters are common place (practically guaranteed) in anything that costs less than £100, and pretty common in items up to £500 and above. My favourite one is when manufacturers use spherical cut lenses or mirrors to save money, the reason this is ironic, is that the special corrector lens costs more than a properly ground lens.

[cplmac]

Like Andrew said, a good lens filter will clear up about 90% of that problem, make sure you get an anti-glare lens it's mandatory for pyro video. We use a Sony FX-1 with an anti-glare lens and it rarely has the flare that my Olympus does. I've got dozens of flared out videos from that little Olympus.