If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Video mode: sensor vulnerable to lasers
Be careful when using video mode (or long exposures) when lasers are around.
http://vimeo.com/13450755 -- gmail originated posts are filtered due to spam. |
#2
|
|||
|
|||
Video mode: sensor vulnerable to lasers
Alan Browne wrote:
Be careful when using video mode (or long exposures) when lasers are around. http://vimeo.com/13450755 Even worse: http://www.reuters.com/article/idUSL...080714?sp=true |
#3
|
|||
|
|||
Video mode: sensor vulnerable to lasers
"Alan Browne" wrote in message ... Be careful when using video mode (or long exposures) when lasers are around. http://vimeo.com/13450755 Would EVF based cameras will have the same vulnerability at all times? |
#4
|
|||
|
|||
Video mode: sensor vulnerable to lasers
On 10-08-09 17:57 , OG wrote:
"Alan wrote in message ... Be careful when using video mode (or long exposures) when lasers are around. http://vimeo.com/13450755 Would EVF based cameras will have the same vulnerability at all times? A good point - I would assume so. It's germane to note that, in the video shown, only one (or a few) site failed but all the pixels to the right of it are then rendered useless as their image data can't be bucket brigaded off of the sensor (this explains the straight line failure). -- gmail originated posts are filtered due to spam. |
#5
|
|||
|
|||
Video mode: sensor vulnerable to lasers
On 10-08-09 16:07 , Me wrote:
Alan Browne wrote: Be careful when using video mode (or long exposures) when lasers are around. http://vimeo.com/13450755 Even worse: http://www.reuters.com/article/idUSL...080714?sp=true I remember seeing a documentary excerpt on setting up lights at rock concerts in the late 80's. There were always 1 or 2 "laser nazi's" in charge of making sure the lasers are setup safely and that they "dump" into something absorbent. I think this discipline is missing in Russia and likely fading elsewhere. (In a Pink Floyd video a roadie lights his cigarette with a laser...) The Russian military (Navy) have been known to light US and Canadian patrol aircraft with lasers. This resulted in vision damage to a Canadian helicopter crew in the early 2000's - included a US officer who was also affected. -- gmail originated posts are filtered due to spam. |
#6
|
|||
|
|||
Video mode: sensor vulnerable to lasers
On Mon, 9 Aug 2010 13:51:58 -0700 (PDT), RichA
wrote: On Aug 9, 4:07*pm, Me wrote: Alan Browne wrote: Be careful when using video mode (or long exposures) when lasers are around. http://vimeo.com/13450755 Even worse: http://www.reuters.com/article/idUSL...080714?sp=true Brainless to fire a Argon laser into a crowd instead of over their heads. Even those little frequency-shifted green pocket lasers can do damage, let alone an industrial entertainment laser. Especially when they are pot-modded to ~100mw. I had a couple visitors here yesterday, their son wanted to play with my 405nm and green laser pointers that I have. ($7.95 w/ free shipping from China on E-Bait, but their potentiometers are adjusted to 5mw to get them through customs.) I especially like the green pot-modded ones. The beam (not just terminal dot) is brightly visible in the air in full sunlight. He was having fun lighting matches with them. I warned him to not stare at the focused beam on the paper-matches too intently. He was seeing spots for quite awhile.The 405nm blue laser (same price) is interesting when pot-modded to ~100mw. It makes some fist-sized crystals I dug out of my rock-shop phosphoresce in a bright magenta color. As you sweep the laser over the crystals it leaves a trace of bright magenta for about 1/4th second. This phosphorescence undetectable under short and long-wave UV. It must be the intensity of the light that causes it. A pot-modded 405nm laser should be in every rock-hound's bag of investigative tools. I've no doubt they'll open up a whole new type of minerals out there now. Categories of short-wave UV fluorescence/phosphorescence, long-wave UV fluorescence/phosphorescence, and blue-laser fluorescence/phosphorescence. |
#7
|
|||
|
|||
Video mode: sensor vulnerable to lasers
On Tue, 10 Aug 2010 14:05:47 -0700 (PDT), RichA
wrote: On Aug 9, 8:08*pm, R Davis wrote: On Mon, 9 Aug 2010 13:51:58 -0700 (PDT), RichA wrote: On Aug 9, 4:07*pm, Me wrote: Alan Browne wrote: Be careful when using video mode (or long exposures) when lasers are around. http://vimeo.com/13450755 Even worse: http://www.reuters.com/article/idUSL...080714?sp=true Brainless to fire a Argon laser into a crowd instead of over their heads. *Even those little frequency-shifted green pocket lasers can do damage, let alone an industrial entertainment laser. Especially when they are pot-modded to ~100mw. I had a couple visitors here yesterday, their son wanted to play with my 405nm and green laser pointers that I have. ($7.95 w/ free shipping from China on E-Bait, but their potentiometers are adjusted to 5mw to get them through customs.) I especially like the green pot-modded ones. The beam (not just terminal dot) is brightly visible in the air in full sunlight. He was having fun lighting matches with them. I warned him to not stare at the focused beam on the paper-matches too intently. He was seeing spots for quite awhile.The 405nm blue laser (same price) is interesting when pot-modded to ~100mw. It makes some fist-sized crystals I dug out of my rock-shop phosphoresce in a bright magenta color. As you sweep the laser over the crystals it leaves a trace of bright magenta for about 1/4th second. This phosphorescence undetectable under short and long-wave UV. It must be the intensity of the light that causes it. A pot-modded 405nm laser should be in every rock-hound's bag of investigative tools. I've no doubt they'll open up a whole new type of minerals out there now. Categories of short-wave UV fluorescence/phosphorescence, long-wave UV fluorescence/phosphorescence, and blue-laser fluorescence/phosphorescence. What is the crystal? I never bothered to ID it, I have many many projects always in the works. But now that you ask ... (went to go get it) ... it's going to be a little difficult, because the crystalline structure is trapped in a matrix of what appears to be a kind of light colored basalt. The cleavage planes of the crystals are clear and large with a satiny vitreous appearance, but there are no crystals projecting beyond the conglomerate to determine any clear planes of growth. All cleavage planes of the large embedded crystals are also at unique angles to one another. (After more looking, I found one set of cleavage (or growth) planes at 90 degrees to each other, and another set at about 60 degrees to each other.) They are a light translucent grayish-white. Softer than a pocket-knife blade. So I suspect a form of calcite (many forms of calcite fluoresce yellows or greens, usually with a long duration phosphorescence) or maybe dolomite. It almost looks like a pale chabazite, some of the crystals have random inclusions of a rusty pink. This is where a further ID key of "blue-laser effects" in rock and mineral books would come in handy. If under the blue-laser listing it said, "Phosphoresces for about 1/4th second in bright magenta", then I could tell you right off what it was. I know fluorite will fluoresce under UV light, but I don't know which crystals display phosphorescence. Many minerals phosphoresce. To the dark-adapted eye, many calcites will continue to glow a dull green, orange, or yellow for many many minutes after exposed to UV. Barely visible, but its there. For minerals with very short duration phosphorescence they polish a sample of the mineral into a sphere, then spin it rapidly on its axis in the presence of strong short-wave or long-wave UV light. They determine the duration of phosphorescence by how far the glow is wrapped around to the back unlit portion of the spinning sphere, the time calculated from the RPMs. I had thought it might be an interesting photography dilemma to solve. I've been wanting to send photos of the mineral's behavior under blue-laser to a few friends. But how to expose for the bright magenta phosphorescence that trails behind the bright blue laser played across its surface, and not overexpose those same traced areas with the 100mw laser. I really can't think of a simple way around it, other than maybe using a strong orange filter to filter out the laser frequency. Unfiltered video might work. Then just pull out a frame with the best example. Perhaps CHDK might come to the rescue. Using it's motion-detection I could set it to detect a change of light in the FOV, set shutter for about 1/4th second. No, that wouldn't work. It would start exposing on the first laser detection. I need it to expose for the light left behind the moving laser. Maybe if I move the laser across its surface faster than the motion-detection trigger time of 45ms. That would do it. The laser would have left the FOV and the camera would only capture the trail left behind. Still though, video would be more impressive, it's neat to see the many swirls of magenta glow all around where the laser was played. An interesting photography dilemma I've not run into before. I might try a solve-by-doing tonight, if I get a break in feeding about 50-60 wild critters. My normal 'til sunrise routine. Got some nice infrared shots last night of a Barred Owl 10 ft. up a tree above where I was feeding and hand-feeding the critters. It didn't seem to be phased by my being within a couple yards of it. Perhaps it sensed safety from how many wild animals would follow me around the yard or eat out of my hands. It was getting some of the mice and voles that go for the crumbs the larger critters gluttonously drop into the grass. I watched it catch a couple when I went back inside. I was a little concerned for all the smaller raccoon cubs' safety, but the owl itself was on the smaller side. If nothing else, all the cubs milling around got to learn about owls. Their mothers most curious about the scent of the owl after it flew back into the tree, intently checking out where it had landed and subdued its prey for a few moments. A random grab, Barred Owl in infrared. (JPG degradation intentional) Note its posture, it could care less that I was there. It was busy watching all the raccoons, foxes, opossums, and food dishes. Hoping to spot a darting mouse or vole amongst them all. http://farm5.static.flickr.com/4118/4881074056_e8ab34ec2c_z.jpg The IR videos are more impressive. It was interesting to watch how the owl would move its face in a full circular motion, in a flat plane to the direction of what it was trying to detect. Bobbing its head low, then to the right, up, to the left, and down again in one large and smooth full circular motion, while keeping its eyes on the same spot. It appeared to be using its stereo hearing in more than one plane, not just left/right but top to bottom too. Like making a larger listening-dish out of its hearing by sweeping a larger area of the received sound. |
#8
|
|||
|
|||
Video mode: sensor vulnerable to lasers
In article , R Davis
writes Especially when they are pot-modded to ~100mw. I had a couple visitors here yesterday, their son wanted to play with my 405nm and green laser pointers that I have. ($7.95 w/ free shipping from China on E-Bait, but their potentiometers are adjusted to 5mw to get them through customs.) I especially like the green pot-modded ones. The beam (not just terminal dot) is brightly visible in the air in full sunlight. He was having fun lighting matches with them. I warned him to not stare at the focused beam on the paper-matches too intently. He was seeing spots for quite awhile. See this before letting anyone "play" with your cheap green laser pointer. http://www.nist.gov/customcf/get_pdf.cfm?pub_id=906138 Even if you think your GLP is low power and relatively dim, chances are it is emitting enough invisible 808 & 1064nm to permanently damage your retina. You can see the green beam, so blink reflex provides a significant natural protection against retinal damage. You can't see 808 & 1064nm, so no blink reflex and no natural protection - a real danger when some GLPs emit more than 10x as much power at these wavelengths as they do in the green. Sounds like your GLP is leaking a lot of IR if he was "lighting matches" with it - very dodgy. The document link above explains some simple tests to at least check the 808nm output from a GLP using a CD-ROM and a webcam. -- Kennedy Yes, Socrates himself is particularly missed; A lovely little thinker, but a bugger when he's ****ed. Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
#9
|
|||
|
|||
Video mode: sensor vulnerable to lasers
"Kennedy McEwen" wrote in message
... [] See this before letting anyone "play" with your cheap green laser pointer. http://www.nist.gov/customcf/get_pdf.cfm?pub_id=906138 [] The document link above explains some simple tests to at least check the 808nm output from a GLP using a CD-ROM and a webcam. -- Kennedy As someone who used to work with NdYAG lasers at 1064nm, with outputs measured in mega-joules rather than milli-watts, I recall how seriously the chance of eye damage was taken. Thanks for the pointer to that document - interesting as a description of how the devices work as well as for the warning it provides. Cheers, David |
#10
|
|||
|
|||
Video mode: sensor vulnerable to lasers
On Tue, 10 Aug 2010 14:05:47 -0700 (PDT), RichA
wrote: On Aug 9, 8:08*pm, R Davis wrote: On Mon, 9 Aug 2010 13:51:58 -0700 (PDT), RichA wrote: On Aug 9, 4:07*pm, Me wrote: Alan Browne wrote: Be careful when using video mode (or long exposures) when lasers are around. http://vimeo.com/13450755 Even worse: http://www.reuters.com/article/idUSL...080714?sp=true Brainless to fire a Argon laser into a crowd instead of over their heads. *Even those little frequency-shifted green pocket lasers can do damage, let alone an industrial entertainment laser. Especially when they are pot-modded to ~100mw. I had a couple visitors here yesterday, their son wanted to play with my 405nm and green laser pointers that I have. ($7.95 w/ free shipping from China on E-Bait, but their potentiometers are adjusted to 5mw to get them through customs.) I especially like the green pot-modded ones. The beam (not just terminal dot) is brightly visible in the air in full sunlight. He was having fun lighting matches with them. I warned him to not stare at the focused beam on the paper-matches too intently. He was seeing spots for quite awhile.The 405nm blue laser (same price) is interesting when pot-modded to ~100mw. It makes some fist-sized crystals I dug out of my rock-shop phosphoresce in a bright magenta color. As you sweep the laser over the crystals it leaves a trace of bright magenta for about 1/4th second. This phosphorescence undetectable under short and long-wave UV. It must be the intensity of the light that causes it. A pot-modded 405nm laser should be in every rock-hound's bag of investigative tools. I've no doubt they'll open up a whole new type of minerals out there now. Categories of short-wave UV fluorescence/phosphorescence, long-wave UV fluorescence/phosphorescence, and blue-laser fluorescence/phosphorescence. What is the crystal? I know fluorite will fluoresce under UV light, but I don't know which crystals display phosphorescence. Some sulfides emit light when bombarded by energetic radiation. http://www.pbase.com/andersonrm/image/103477978 I have a rock that responds this way, I believe it is a Terlingua type calcite. when hit with either the blue or green laser the whole rock lights up, looks like it is illuminated from inside. |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Battery life in video mode - Canon 5D-II and Nikon D90. | Alan Browne | Digital SLR Cameras | 1 | September 23rd 08 10:30 AM |
Sensor cleaning mode maps out hot pixels | [email protected] | Digital Photography | 46 | April 5th 06 08:36 AM |
Canon SD200 red bleeding in video mode | Brad P | Digital Photography | 0 | February 26th 06 02:47 AM |
SONY P100 in Video Mode | Vince | Digital Point & Shoot Cameras | 0 | September 12th 05 05:35 PM |
Video/movie mode with zoom | [email protected] | Digital Photography | 4 | December 24th 04 08:51 AM |