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Damage to CCD'S


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#1 Kieran Scannell

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Posted 25 February 2008 - 04:47 PM

I'm shooting a documentary on a HDW-750, some of it will be shot at a dance event, massive crowds and a lot of lasers, now i know a prolonged exposure to laser directly hitting the ccd's will
damage them but I've been hearing horror story's from DP's that after a 4 hour shoot in a disco
they ruined 2 camera's. There's one particular shot I'm worried about, on the dance floor moving
through the crowd as it parts for the DJ.

Should i be worried?

Kieran
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#2 Phil Rhodes

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Posted 25 February 2008 - 09:38 PM

I've seen a DXC-35 wrecked like that so yes you should.
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#3 Cesar Rubio

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Posted 25 February 2008 - 10:43 PM

I've seen a DXC-35 wrecked like that so yes you should.



Phil:

Do you know if that applies to CMOS as well?

Thanks,

Cesar Rubio.
Cambridge Wisconsin, USA.
http://www.davidrubio3d.com/
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#4 Markus Rave

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Posted 26 February 2008 - 05:49 AM

You shouldn´t be worried while shooting on the dancefloor but I strongly recommend not to point the lens directly into a laser. If the rays hit you on the dancefloor it will not harm the CCD but pointing right into the source even stopped far down holds a very high risk to damage the CCD. I remember a production where this was the case with a DVW 700. Afterwards we found multiple pixel failures. Could be corrected later by resetting and recalibrating black level but since exposure to the rays was not for a prolongued time this might not be possible in every case.
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#5 Phil Rhodes

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Posted 26 February 2008 - 10:37 AM

> Do you know if that applies to CMOS as well?

It's the same technology at the level of the individual photosite, so I would assume so.

P
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#6 Walter Graff

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Posted 26 February 2008 - 11:07 AM

Both CMOS and CCD are suceptable to damage by lasers and that damage is not necessarily dependant on exposure length. A simple pulse could cause damage. Color is a big factor and lasers closer to blue and green in frequency are more dangerous to CCDs than Red.
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#7 Kieran Scannell

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Posted 26 February 2008 - 02:01 PM

Thanks everyone!

Kieran.
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#8 Keith Walters

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Posted 27 February 2008 - 04:10 AM

The problem is that, if a laser hits you in the eye, you immediately blink or look away, so low powered lasers are considered safe for entertainment use. A camera is not that smart, and also, on a monitor, a 10,000% overloaded pixel tends to look little different from a 100% overloaded pixel!

Actually I've got some old CCD colour CCTV cameras in my junk box, it might be interesting to see what happens if I point a 5 milliwatt laser pointer at one of them for a while :rolleyes:
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#9 John Sprung

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Posted 27 February 2008 - 01:30 PM

Actually I've got some old CCD colour CCTV cameras in my junk box, it might be interesting to see what happens if I point a 5 milliwatt laser pointer at one of them for a while :rolleyes:

It would be interesting to see if it's a threshhold thing, or cumulative exposure -- Is 1 mSec at 100% intensity the same as 10 mSec at 10%?



-- J.S.
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#10 Phil Rhodes

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Posted 27 February 2008 - 06:42 PM

You'd have thought not, because it's a thermal issue - the slower you do it, the faster you can conduct the heat away through the substrate of the sensor.

The damage I witnessed occurred while the laser was scanning a plane which intersected the lens at such an axis as to fall on the sensor. It only took about eight seconds - the centre of the huge flare remained dark after the stimulation was removed. It was an argon-krypton gas laser, so green, not sure of the output but definitely multi-watt.

P
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#11 david west

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Posted 27 February 2008 - 07:00 PM

this is an interesting topic in that to a mild extent the sun and to an extreme extent lasers both damage vid sensors. this has been my personal thought as to why film will never totally die. there are some shots that you just dont want to take since they can ruin an expensive vid cam.

i remember reading years ago about vandals destroying security cams with lasers... now we have lasers everywhere.

in the early eighties a psy prof was let go from USC for doing laser experiments on himself. he would point the laser at his own eye for a brief moment. result: a small blind spot. a few days later the blind spot would be filled back in, BUT- just like the blind spot from the optic nerve, the blind spot was still there--- just gone perceptually.

My point- (since i tend to ramble) is that it is not only the camera that is at risk, but protect your eyes around lasers as well....
cheers
dbw
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