730-740nm is NOT infrared

[Krane]

I wanted a really deep red LED, so I purchased a $4 - 5W and the description said 740-745nm, while the envelope it came in said 730nm, unfortunately, I have no idea of how to measure, however, it would be considered and is considered to be infrared -- well by far it is not.


1. If you google human vision spectrum you get a complete cutoff at these wavelengths in some charts, and a little beyond that in other charts, none of the charts actually represent the human vision that well, it is mostly guess-work type deal.

2. I came to this conclusion because I used the front iPad camera as well as rear, and both cameras showed about the same brightness, I intend on checking again once it gets darker, the reason it should have been different if this was infra-red is that the rear camera has a very good infrared filter, front camera shows infra-red as bright purple (try your remote control).

3. Description None of the computer screens could ever display this light, and I doubt any camera apart from film could either. If you have seen the latest sportier Mercedes AMG like 2019 models (I will update with a specific car model when I see one again) -- I believe they use this wavelength for their tail lights. I have been mesmerized a few times what is that new red tint Mercedes is using, and by pure luck this is exactly what I got in the mail today.

If you ever saw the faint red glow of 820nm IR camera -- I would say it is similar tint red, but without the IR part, and much much brighter than IR (to the eye).

4. It does not look very bright unless you look straight into it, and it does strain your eyes if you look into it your irises will contract, illumination per watt is lower than that of regular 630-640nm, however ~650nm looks orange in comparison to this, this looks evil.

Suffice to say -- our eyes are not sensitive to this wavelength, but it is definitely red and not infrared.


Plan: I will leave the flashlight I frankensteined this LED into running until its almost dead, and when it is very dim I will test it with the front iPhone camera to see if there is any "white" looking residual IR light coming out of it.


P.S. If you shine this LED through a very deep blue glass filter -- it makes that filter completely transparent and see through:thinking:

 

[archimedes]

There are numerous confusing and likely inaccurate statements in your post.

The concerning part however is that some of what you describe above may be potentially harmful

 

[archimedes]

This link might be a useful starting point ...

https://ehs.lbl.gov/resource/docume...izing-radiation/light-and-infrared-radiation/

 

[WalkIntoTheLight]

I'm not sure what the OP is getting at, but 730nm is considered to be near-infrared. Most people can't see this. However, that doesn't mean a 730nm LED is not leaking some red light in wavelengths shorter than 700nm, which is likely what you're seeing.

If you really want to remove the visible light, take your IR source and stick a filter over it, like a B&W Infrared 093 camera lens filter. Though, you might need a LED with longer wavelengths than 730nm. You could try a Hoya R72 infrared filter with your 730nm LED. That should remove almost all visible light.

 

[MeMeMe]

As said above. LEDs are not a single wavelength. They have a Gaussian emission distribution not to mention a MFG distribution. That wavelength is targeted at plant growth not being invisible.

 

[Krane]

As said above. LEDs are not a single wavelength. They have a Gaussian emission distribution not to mention a MFG distribution. That wavelength is targeted at plant growth not being invisible.

I assure you it is a very narrow wavelength, the grow LED's are full spectrum and are purple, this is not

 

[Krane]

I'm not sure what the OP is getting at, but 730nm is considered to be near-infrared. Most people can't see this. However, that doesn't mean a 730nm LED is not leaking some red light in wavelengths shorter than 700nm, which is likely what you're seeing.

If you really want to remove the visible light, take your IR source and stick a filter over it, like a B&W Infrared 093 camera lens filter. Though, you might need a LED with longer wavelengths than 730nm. You could try a Hoya R72 infrared filter with your 730nm LED. That should remove almost all visible light.

I assure you it is not infra-red, I have used an infra-red blocking lens and the intensity did not change a bit, not to the eye, not to the camera, the light itself is intense, to the camera, and less so to the eye because we arent sensitive in that region, so that is the only thing to pay attention to and i made sure not to shine it in my eyes because it was unpleasant, so the eye response protects me from doing anything stupid.

I am open to more testing, yes its the reagion where IR starts to overlap,

• IR‐A (near-infrared): 760 and 1,400 nm -- this means that my LED 730nm-745nm is still in the safe region, the IR starts to creep in at 760 nm according to this article https://ehs.lbl.gov/resource/docume...izing-radiation/light-and-infrared-radiation/

 

[Krane]

This link might be a useful starting point ...

https://ehs.lbl.gov/resource/docume...izing-radiation/light-and-infrared-radiation/

thank you! says im safe IR starts to creep in around 760nm, the LED is 730-745, besides I do feel the intensity with my eyes its unpleasant i dont shine it in my face anymore

 

[altermann]

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[MeMeMe]

I assure you it is a very narrow wavelength, the grow LED's are full spectrum and are purple, this is not

So you have a spectrophotometer?

It does not have a very narrow wavelength. LEDs in general do not, 730-740nm do not.

LED grow lights are many colors, blue, around 450-460nm being ones, 650-660nm being another, though far less efficient 630nm are often substituted. 730-740nm is another color that is used to stimulate different growth mechanisms.

Here are some typical 730nm LED spectrum with a ton of light <700nm.

See what is described as far red below

This is the OSRAM data sheet for the most popular commercial 730nm LED: https://www.osram.com/ecat/OSLON® S...catalog_103489/global/prd_pim_device_2402545/

 

[MeMeMe]

• IR‐A (near-infrared): 760 and 1,400 nm -- this means that my LED 730nm-745nm is still in the safe region, the IR starts to creep in at 760 nm according to this article https://ehs.lbl.gov/resource/docume...izing-radiation/light-and-infrared-radiation/

That's not what that article says. It says that any wavelength can be dangerous. A 730nm LED can be dangerous because it is not perceived as bright and will not generate the typical response that intense visible light will cause (i.e. turning away).

• Thermal damage of the iris, approximately 380–1,400 nm
• Near-infrared thermal damage of the crystalline lens, approximately 800–3,000 nm
• Thermal damage of the retina 380–1,400 nm

 

[WalkIntoTheLight]

I assure you it is not infra-red, I have used an infra-red blocking lens and the intensity did not change a bit, not to the eye, not to the camera, the light itself is intense, to the camera, and less so to the eye because we arent sensitive in that region, so that is the only thing to pay attention to and i made sure not to shine it in my eyes because it was unpleasant, so the eye response protects me from doing anything stupid.

A 730nm LED is going to be emitting lots of infrared and visible light. Even if your IR blocking filter blocked 100% of the infrared (which is doubtful), you're still going to be seeing the visible red light.