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A question of power

Jondblake

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Hi guys,

I’m new to the forum, and lasers in general. I’m trying to research out a purchase of a laser and found your site, which seems like the perfect place to get educated. I’ve been reading previous posts and searching but can’t really find the answer to my question. I’m hoping or more of you are willing to help me out with your opinion if you don’t have first hand knowledge to my question(s).

I’m a landscape photographer who’s recently gotten into shooting at night, where focus has become an issue. The main thing I’m trying to figure out is what is the approximate maximum distance of a 5mW green laser for me to be able to focus on. I realize that you guys may not be photographers, so what is the maximum distance the beam can be seen? A couple miles or just a few thousand feet? I’d really prefer to keep the power down for safety reasons if it’s powerful enough to satisfy my needs.
 

Blaster

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Hi and welcome ..first off a 5mW laser is rare most are well over that ,by up to 15 times (by whats shown on the sticker for rated output)as far as distance to focus on about 500m for a 5mW laser but as said most are a lot over what is shown on sticker, a 100mW green 532nm laser is easy visible 5km away but the dot only depends on how you are viewing it. Your eyes cant see that far in the dark, or barely but a lenses on the camera telephoto, you will see no problem .in other words the dot is there but your eyes don't have the magnification see a dot so far away your camera telephoto lens will see it.
 
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Jondblake

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Thanks Blaster.

The way I plan to use the laser is to fix it on a clamp on my tripod, aimed on a fixed object. I shoot wide angle normally, but he camera has live view which allows me to zoom in digitally giving a virtual magnification. It certainly isn't the same as putting on a telephoto lens, but it does provide enough magnification to focus on far away things(such as a bright star for example).

I've read about the power fluctuations you mentioned in numerous threads. I guess in theory I don't have a big problem with having more power, other than the possible safety issues. Am I correct in saying that if I were to actually receive a 5mW laser then I would not need eye protection, but would need it if the laser I recieve is more powerful? And, that's why it's recommended that safety glasses be worn under all circumstances and/or testing is necessary after it's received? Or am I wrong that even a 5mW laser will do eye damage and under any circumstances safety glasses should be worn?
 

Blaster

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Yes eye protection at over 5mW, but witbout knowing if your laser is 5mW ,always play it safe ...only way to know power is with a LPM laser power meter and they are very expensive, but not as much as your eyes are which are Priceless, if at night pointing away from yourself you can be mostly sure with commonsense you will be fine, ie don't look down the beam to the laser exit point looking on side of the beam of light is totally safe ,A high power laser at night can be seen from space at 50 to 80 km of course these are expensive, but not redicoulously so a fraction of a second of any laser in the eye and you would be permanently injured or blind, that's for the very high power lasers and lesser as well but you may have a chance being hit in the eye with A 100 mW green and possibly not getting permanent damage but you would still get serious damage without a doubt that may or may nor repair its self over a long period of time . lasers are lovely to behold but not toys and need to be treated with a great deal of respect
 
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..first off a 5mW laser is rare most are well over that ,by up to 15 times (by whats shown on the sticker for rated output)
I must share this has NOT been my experience. Perhaps 2 or 3 years ago, it wasn't easy for manufacturers in China to throttle back (532nm green, in particular) lasers to genuinely be under 5mW.

But in the last year, I've ordered maybe 10 or so pen-style 2xAAA battery pen lasers, and not a one has measured more than 10mW. More than half have indeed measured below 5mW, to my dismay.

With that said, they certainly DO vary in output. I don't think the seller has much concern if the laser pointer is OVER the rated specification. They all say 5mW to adhere (rather loosely) to US regulations.

Further, the Chinese are getting smarter, in that when they find an efficient pointer with decent output, I suspect they pull it aside and sell it for more $$$.

The bottom line is we cannot trust what it says on the label. It may be over, it may be under. The only sure way to know with any accuracy, is to use an LPM. However, if you own large collections of measured lasers, you can compare their outputs, side-by-side and get a rough estimate. But many newcomers don't posses such a collection.
 

Blaster

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I just seem to have gotten a great batch of lasers and eBay pens that are way way overspec ,i feel your pain the first lots i got where low power 10mw still not safe but lately i got a heap of all three colors and all where and still are at least 10 times over the sticker on the label, i was so happy with the first few i got i went and bought 12 more of each same seller same batch and after a year or more i haven't killed one yet either the older ones or the new ones ..my latest batch of 650nm reds are putting out a Rock solid 160mW which is fantastic for a 8 dollar pen, ive used them heaps still perfect
 
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Jondblake

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Great information, thanks! Now to find that thread with the various company recommendations and find the cheapest IR filtered 5mW green laser with a lockable on/off switch. I’ll let you know where I end up going. In my research thus far I found the Laserglow Galileo which seems to have everything I want. Before I purchase, I’m going to see if there’s a competitor out there with a similar product at a better price.

On a related note, am I correct there's a debate as to the level of damage which can be received from the IR light associated with green lasers? Also, that the IR is emitted from the laser in similar fashion as the green beam, but at a larger diameter, which since it's unseen, creates the danger?

My buddy, a fellow night photographer, bought a cheap 50mW laser pointer. After hearing about the IR damage possibilities wanted me to ask the experts about the potential danger. Is it only if the laser is pointed at someone, or is there a contingency of folks who believe that any un-IR-filtered green laser is dangerous to the user whether pointed at them or not. I know this is a highly debated issue and I’m not intending to open up a can of worms. I’m just asking about the boundaries of the arguments. For example, if everyone agrees that there’s no danger from holding and using the laser is much different than a group who believes that there is danger to do so.
 

NDTCPI

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Not to hijack the discussion... But I too am looking for similar info. Who is the best to buy from for reliability, durability, and warranty. Do the green high power lasers get hot enough to ignite petroleum vapors?
I do various types of inspections and sometimes I need to point things out that are a few hundred feet away. I also will need to use this in the daylight. I don't mind spending the money for a good item. What about Wicked Lasers and their Krypton (?) laser?
Thanks so much for any quality info.

Dave
 




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