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jack620

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I just replaced twelve 36W 120cm/4ft flouro tubes in my workshop with 16W Osram LED tubes in daylight colour (6500K). I don't feel they are any brighter, but I prefer the colour to the old warm white tubes.
 

Wizard69

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Hi Cogsy;

Little late responding.
Not only does it support the "blue is bad" position, it claims the 'formal' range of this damaging spectrum is defined as the "300- to 700-nm range" which covers virtually the entire (human) visible spectrum (our eyes can detect in the range of 380 - 740 nm).
This is why I specifically mentioned that they dived into the blue is bad nonsense.
This is an absurd statement and is directly equivalent to saying "any visible light is damaging to our eyes".
Here in lies the problem wave length doesn't really matter, if the intensity is high enough you can get damage. If not damage, temporary blindness or disorientation. I've actually have had exposure to very high intensity 'RED' LED's and can attest to how bright those little guys can be. However what many need to understand here is that these are not consumer grade light sources.
It goes on to make further preposterous claims and even suggests some equivalence between lasers and LEDs in terms of danger.
Even old fashion light sources like halogen projector bulbs can damage the eyes. This especially in the case of shielded bulbs that don't have UV filtering.
They even make reference to potential thermal hazards of long wavelengths emitted by LEDs, so they are suggesting infrared being emitted by high intensity LEDs is thermally damaging to our eyes! It boggles the mind to imagine how hot an LED would have to be running to essentially 'cook' our eyeballs (remember we detect infrared radiation as the 'hot' sensation we feel whenever we get close to an emitter like a hot stove or fire).
The problem here is that you can make any wavelength of light a hazard by suitably concentrating it.
This 'point source' issue could only possibly be a problem with LEDs (due to their low total power output) if the entirety of the light being emitted was focused on the retina. As the light emitted is multi-directional, unlike a laser, you would have to place the LED virtually touching your eyeball to capture most of the light being emitted. As you move the LED away from your eye, more of the light is missing your eyes and not being collected.
Interestingly this point source issue has been brought up in other articles which unfortunately I could not find when I posted this one. In any event there is certianly a distance issue here as the eye has to be at a distance from the point source to create a point or illumination on the retina.
The way our eyes work is to focus all the light being received into a spot on the retina so an image is resolved. When this focusing process is not occurring on our retina we can't see clearly and we need to wear corrective lenses to correct this focus and let us see properly. There is nothing special about the size of an LED allowing it to be focused to a single spot on our retinas.
It is true that there is nothing special about an LED but there is nothing special about a filament in an old fashion light bulb. There is a difference though in that the light isn't as multi directional as you think. In either case looking at and trying to focus on such light generators is not a good thing to do. I have to believe that your know this and hopefully everybody in this forum does also.
If you're interested in the science behind an issue, the best research option is to read journal articles in peer reviewed literature. Google Scholar is a great place to start (https://scholar.google.com/) but be aware not all journals are created equal -
I've actually have read a lot about this and stand by what I've said. Any damage that is going to happen is going to happen because you have an extremely intense light source and that such sources be they an LED, and old fashion bulb, Welders arc or whatever is not good for you to look at directly.
you need to evaluate the reputation of a journal even when it claims to be peer reviewed. The internet being what it is (namely driven by the almighty advertising dollar) clicks are currency and so much of what is written is simply to try and garner traffic. The article you've linked to is a great example of sensationalist misinformation that exists simply to make money.
Err no! It is poorly written that is for sure and likely is gleaning information from research they don't understand, but the main point is that correct. That is very high intensity light sources can be very bad for you.

The problem is people really don't understand what very high intensity light sources are!!!! Beyond that trying to explain the the inverse square law is sometime futile. However in this hobby I think it is important to get people to respect high intensity light sources if they ever have an opportunity to work on one. Care should be taken for example in installing and adjusting a bulb in a profile projector or the like.

Further what is important here is to realize there is a huge difference between a high intensity light source and a video monitor or even LED lighting. LED lighting solves the problem or a high intensity source by the use of diffusers.

By the way LED's themselves are very interesting to read about. There are many approaches to getting the light out of the LED. This shapes the light projected from the LED which is why you can't really compare them to multi directional light sources like fluorescent or filament bulbs. LED's may not be lasers but they are also not homogeneous in the way that they perform.
 

Cogsy

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Little late responding.
.
Hi Wizard,
I'm not going to address your post point-by-point, and certainly not going to go through the thermodynamics as to why a 3W, 5W or even higher wattage LED can't thermally damage your eye, or go through the difference between (even 'high' intensity) LED light and narrow-band, phased LASER light emission, but instead I'm just going to elaborate on where I'm coming from on this topic. I have a degree in Physics and I'm currently doing post-grad research into ocular biophysics, which is likely to evolve into my PhD thesis topic. Without trying to be arrogant, I do assume that I have a little better background and understanding of this area than a layman, although I'm certainly not a world authority. If/where I am wrong I'm more than happy to be corrected, but the unreviewed site/article you originally linked to is very poor quality and is talking a large amount of bunk.

LEDs' can be very bright, and as a general rule, if the brightness of any light source feels unpleasant, then don't look at it. As far as damaging your eyes from an LED in the manners described in that article - completely unsupported/ utter garbage.
 

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