Some Semi-Scientific Rambling: Surprises about Flashlights & How We See
Some people read part of my post in another thread and pushed me to begin a new thread because they thought people would find it interesting.
Allow me to begin by quoting Boaz. He made some really good comments in yet another thread. He actually made several and it’s worth reading the whole thread. (It’s a short one.)
https://budgetlightforum.com/t/-/12665#comment-257515
Boaz has the unique ability for expressing important and interesting points with the addition of some welcome humor. This is what he said in the other thread:
“OMG you can't say that !!!!
It's Mr. perfect tint ...LOL
Anonymous third party quote: “It is a great emitter and it is slightly rose' ...”
Back to comments from Boaz:
The discussion about tint always seems to blow me away ..
If you understand the inverse square law than you understand that there is virtually NO difference in a 600Lumen light and a 800lumen light ,, you can't even really see the difference ..
A neutral white tint is 7% less lumens ...NOT visual output .. The inverse square law states you need to quadruple your output /lumens numbers to see a doubling of light ..
So I see people trying to preserve a unperceivable amount of light .(Something they CAN’T SEE ) for a tint that is hugely obvious .. This makes Zero sense to me. People trading a real gain for nothing...All because somehow they want to think one is brighter ....just crazy..
Most people will say that a throwy light is brighter than a floody light too ... when in some cases it is less than half the lumens ... the numbers really don't mean squat and until you stop measuring tv's by pixels or some easy numbers that manufacturers so easily lie about or toss out, then you'll be endlessly fooling yourself .
So it appears according to the election it's easier to sell people using fear .. So lets do that ..CW makes you want to commit violence ..it's hugely bad purple and blue light ..most of which you don't see till you compare a better tint to it ..CW washes out all color and creates glaring . it makes all items seem like they are cardboard cut outs .. if you buy neutrals women will like you better ”
Back to my – KumaBear’s comments:
In fact, the entire thread “some semi-scientific thoughts on LED tint” is just one of several very interesting related threads.
I am also particularly interested in High CRI and have read some threads that were contributed to or begun by Vectrex and others who take an interest in (and have some excellent understanding of) the subject.
Having had a little scientific training in this subject and having done some hands-on experimentation, I’d like to share some facts that you’re likely to find either unbelievable or very interesting.
Either way, it’s my hope that they will be provocative.
I’m about to depart from the subject of flashlights for a little bit - but please allow me to relate part of an experiment done by Edwin Land (founder of Polaroid and a serial inventor). I believe the experiment was done in the 50s after Land invented the polarizing filter. (As I said, my guess is that you will not believe what I’m about to describe – but I replicated a form of the experiment as part of a junior high school science project.)
Please read on because it really is quite fascinating:
1) Take two slide projectors with black and white (not color) slides, both taken of the same scene.
2) Then, superimpose the images on an ordinary screen but in a dark room.
3) Take a narrowband red filter and attach it to the front of one of the projector lenses.
4) Now, look at the superimposed images on the screen.
5) The Big Question – what do you see?
6) The amazing answer – you see/perceive a scene with a full spectrum of colors!
Why???? Well, I have a T-Shirt that says “I can explain it to you but I can’t understand it for you.” To be frank, I still don’t totally understand this phenomenon but there is a great write-up of the experiment in addition to a couple others along the same lines in an old Scientific American magazine.
By the way, Land did pursue the phenomenon as a potential method for producing his first marketable instant color film.
I asked him why he didn’t end up commercializing the results and part of the answer had to do with his inability to get adequate color saturation.
ADDENDUM #1) There is a little more to this than I’m describing but one key point is that the two slides were taken under different circumstances. Yes, they were both taken with black and white film but one was taken with a red filter on the lens and the other was not.
Other scientists, layman and photographers would say that comes nowhere near explaining how two black and white slides and one red filter can produce a spectrum of color. Before seeing it for themselves everyone you query will predict that you will produce an image that ranges in color from red to black with various shades of pink in-between.
The traditional view of how the eye perceives light and color were challenged by the results of this and related experiments and to this day, the whole “rod and cone” explanation and all that goes along with it survives pretty much intact regardless.
ADDENDUM #2) I could go on for pages about this topic but this is neither the time nor the place for that type of dissertation.
Here is a link to a very limited and abbreviated discussion of the “Land Effect” as it has come to be named:
http://www.aw3rd.us/scief/colorviz.htm
ADDENDUM #3) My son and I revisited the subject of Land’s experiments with color and human perception of same when it was his time to produce a science experiment back in 1993. We actually demonstrated the effect in a totally different manner – something that I’ll have to write up for anyone that might be interested.
Back to a subject relevant to the BLF and flashlights:
I have taken a keen interest in High CRI LEDs – not what Cree calls High CRI, but something well into the 90 plus percent range. In reading comments and discussing this subject with quite a few members, I’ve found that it’s a subject that most people have trouble “getting their heads around.”
The difference between a CW XML and an NW XML is in the difference between the AVERAGE spectral temperatures of the light they produce – as measured in Kelvin. It turns out that neither LED, whatever Kelvin you decide is NW, will actually reflect back the full range of real life colors proportionate to the way they appear under “natural light.” In fact, the difference is huge. Let me suggest we set aside what we want to call “natural light” for the moment and concentrate on what those LEDs are doing to what we actually see when we shine one of our flashlights on a colorful scene at night.
This subject has also been covered in other threads and I don’t want to go on forever but what is clear is that there are a lot misconceptions and misunderstandings.
Allow me to be intentionally provocative for a moment – the purpose being to stimulate interesting debate and encourage others to “pick these points up where I leave off.”
A) The beam comparisons that we see in tests are interesting, fun, and instructive but often highly misleading – and what appears to be a significant difference in output intensity (accurately measured in lumens) is (as Boaz pointed out) totally unimportant. Take one of the lights out to walk your dog tonight and take the other out tomorrow night. All else being equal, you won’t notice a difference even though there is a rather large difference in lumens.
B) The binning and labeling process that Cree uses leaves a lot to chance. An LED that is rated as having a higher output may indeed have a lower output as measured by accurate instruments – that’s partly because the process is simply not that accurate (something that Cree admits in their specs – and it may be even less accurate than they say- or than sellers would have you believe). Add that fact to the logarithmic nature of the eye’s sensitivity to light and these numbers that we throw around with so much import, should be taken far more lightly (pardon the pun).
C) IMHO, almost all of us (and I include myself here), make buying decisions based on the wrong criteria!
D) COLOR ACCURACY gets short shrift: Personally, I think it would be great if we could see comparison shots of an array of color construction paper or a colorful real-life scene. I’m not sure how this would be accomplished but if we’re comparing two flashlights, rather than having two photos, how about three – one being taken in “natural light” so that we know what those colors should actually look like.
Granted, its fun to see how far away something can be while still being able to light it up. To cite another example, if you’re riding your bike at night, it’s certainly not as important to see the “natural color” of that pothole in the road as it is to see it in time to avoid it.
Needless to say, there are many examples like the above but I would say that color accuracy has gotten “short shrift” in our discussions and tests – just an opinion (and debate is welcome).
E) “Pencil Beam” vs. “Peripheral Vision”: I often find myself trying to find something in a dark area. A flooder, a zoomer or even a light with a really good usable spill are essential to my practical use of a light. There are those that use their lights strapped to a hunting rifle or some other specialized purpose but how many of us pick up a light simply to impress our friends with how far off it will shine?
Please don’t think I frown on this practice. It’s fun! – And I do it myself. On the other hand, if a light is going to get good use and not be relegated to “shelf-queen” status, how should it function? Again – opinions and debate welcome.
F) Quality, Durability and User Interface: I throw these topics in together solely for lack of time and space. Collectively, these areas are almost always attended to by our fantastic reviewers. I just wish all the manufacturers did the same. I could never be part of the “money is no object crowd” but I do find myself paying more and more attention to these things and my sense is a lot of us are doing ourselves a disservice by ignoring them – more on these topics later
Epilogue: Sorry to bore you with a lot of rambling – just had some time to burn and felt “semi-philosophical” for moment. Take it for what it’s worth.
Regards and Thank You for Listening,
KumaBear Bob
what you see reflected back when you shine a light is not even the same light that left your flashlight 
