Agree.
If our sight can be fooled by 3 narrow bands that does not mean that we don't see and don't distinguish what is in between. Take for example blue LED, then red LED, and look at something green lighted by his lights. Then light it by a green LED and compare.
It is a simple experiment, everyone on this forum can do it.
Similarly, like out hearing can be fooled by 200 and 300 Hz tones as if we hear 100 Hz. But it does not mean that we don't hear real 100 Hz and all 100 Hz sounds that we hear result from mix of 200 and 300 Hz sounds.
A supermarket in this country has recently started selling these LED bulbs under their own brand. The design looks like nothing I've seen before, three "leaves" folded together like a flower in the dark. It creates a hollow centre that IMO should help very well with cooling the LEDs...
Does anyone have any experience with them?
Does anyone have any experience with them?
That's because the bands overlap, red & green quite a bit. If they didn't there would be gaps. There is a huge library of research on this going back decades.
Just for run, look at the red response curve of the eye. Notice anything odd? Can you guess what it does?
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Ok so at my job the machine shop has one of these massive comparators.
An externally hosted image should be here but it was not working when we last tested it.
The light source was from a three leaded mercury arc lamp inside the housing sticking out of the front. The lamp looked like this but with a starter electrode hanging off the side. It only needed 60 volts or so to run.
It also has air intake vents for a fan located in the bottom. These lamps are made to order today and are NOT cheap. The power supply was external and had a Sola transformer, some big filter capacitors, and rheostats to adjust the current. The power supply started to get flakey and eventually failed to ignite the lamp.
I mounted the LED chip on a heatsink inside the housing. The mounting screws had springs under them so the heatsink could be adjusted a bit to help with the focus.
It also has air intake vents for a fan located in the bottom. These lamps are made to order today and are NOT cheap. The power supply was external and had a Sola transformer, some big filter capacitors, and rheostats to adjust the current. The power supply started to get flakey and eventually failed to ignite the lamp.
That is HMI lamp. Typically the problem you describe is not because of the power supply, but because as the lamp gets older it gets harder to ignite. That means that you are exceeding lamps life usage, which than damages your power supply. These lamps have very limited life that in some cases is just a few hundred hours. There most likely is counter that counts lamps life if reset when lamp is exchanged.
HMI lamps are very pricey, and few bigger ones ( 8 KW) go for $ 2K price
Do you mean violet that means stimulation of both red and blue sensors?
I don't buy it. But I agree it is the way to fool imagination.
Yes, violet - how do we see it? And why is it often confused with purple?
There isn't much agreement on the subject, just lots of arguing, audio style.
But if you dig around the digital photography forums you'll find the problem pops up often, violet objects that photograph as blue - flowers frequently.
It's interesting but I've not seen a clear answer yet. I'd welcome any info you might have.
If violet objects photograph as blue that means that it's poor reproduction. Try to light set of paints (or pencils) of all colors by different light sources. Some of them will be dark when lit by white LEDs or luminescent lamps.
Green color, for example, can be really green, or a mix of blue and yellow that fools imagination as if it is real green.
Green color, for example, can be really green, or a mix of blue and yellow that fools imagination as if it is real green.
Yes, violet - how do we see it? And why is it often confused with purple?
There isn't much agreement on the subject, just lots of arguing, audio style.
But if you dig around the digital photography forums you'll find the problem pops up often, violet objects that photograph as blue - flowers frequently.
It's interesting but I've not seen a clear answer yet. I'd welcome any info you might have.
He, he, he Pano - here you could have as much as you want of purple and violet:
Purple - Wikipedia, the free encyclopedia
I think you question needs defining on how we see, or how we capture or how we reproduce, and how we reproduce has to be divided on where - screen or color photo print which is RGB reproduction or CMYK reproduction / print? All of these will skew in certain direction and in some cases shift could be dramatical.
On how we see depends very much on what are we looking at, which is proportion of absorption and reflection which is material and pigment dependent. Certain dies are very critical, particularly the ones that are created with artificial UV protections - the most common are materials for outdoor use such as luggage or outdoor furniture. They appear as one color, but they completely shift when captured ether on film or on digital. Out of those materials what is seen as pure black, when captured shift ether to magenta or to green.
As for the digital cameras, with CCD chips they are all hypersensitive on IR and red parts of spectrum. That is why they all have Cyan type of filter over the chip. In early days of digital that was separate filter placed in front or behind the lens. In very early days it was dychroic filter that caused color shifts when used on view cameras while tilting or swinging lens. Later that filter was corrected and it was installed permanently over the chip as a part of the digital chip/back. The existence of that filter produced file that is always, and still is, low in red color reproduction. This unbalance is corrected by color sync profile specific to the hardware used. In audio term file is equalized, by creating the opposite curve.
So that is first factor to consider in conversation why something is shifted in certain direction. The next factor is reproduction on screen or on paper. RGB will always reproduce much wider color gamut, as long as we are not using moronic Microsoft sRGB profile. This profile, created to equalize viewing on any screen, will dramatically map / shift particular vibrant colors to their neighbors, such as purples to blues, or violet to reds or magentas.
The same stands for CMYK printing that will further compress color gamut, and any time that is done, it will further map out certain colors. The ones that first go are the ones that are strong in saturations. In audio terms, color reproduction suffers as well as from compression. Add to that bad or wrong color sync profile used, and both purples and violets are gone.
Next is under what viewing and lighting condition we are observing proofs. Some paper and inks for inkjet proofers are very sensitive to lighting source and amount of UV component. That will further create another shift for some colors...
After we consider all mentioned variables, very often it is miracle that any color comes correct. And they do not. Even with all conditions perfect, color correction in post is very much needed to correct for all variables. The only way I consider closely matching to particular color is by measuring original material, and matching that in the post to the very reading by RGB / CMYK numbers. Arguing over color reproduction is the same arguing over audio reproduction, hahaha.
This is what PWM does to digital cameras.
As soon as they fix this I'm onboard.
They probably did, my previous workplace has LED tubes for lightning and I've snapped a few pictures with a point-and-shoot, never seen anything of that sort.
Can be solved with more LC filter anyway, both for better light quality, and to pass EMC regulation.
Add: Considering that the entire office is covered by T8 LED tubes, if each tube is a least bit noticeable it would make for some impressive intermodulation effect.
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No, it's not fooling the imagination, if you mix yellow and blue pigments (or yellow and cyan) then they will absorb all colors but green. Thus you see green. That's how subtractive color works.
Thanks for the link, I'll study it. It's great that there is more and more info on the interwebs these days.
Yes, that's what I did with my Phase Linear 4x5 scanning digital camera back (~108 megapixel). IR filter on the back of the lens. I was trying to build RGB LED lighting banks for it, as the IR filter would no longer be needed. Pure colors would have other advantages, too. No IR or UV to excite some paint pigments that do weird things to the scans. Ultramarine is notorious.
Years ago we made an IR video camera by removing the filter on the chip. Worked great! The colors were strange, but it was fun. It was used in a kennel to see what the dogs were doing at night.
Hmmm.... yeah, true enough. Color mapping in the camera and display could account for a lot of that color shift. But I think that the color filters in the camera and display device are also to blame. If the blue filter is cut to cover blue and violet, blue is all the camera will ever see. To the filter and sensor, they are the same color. Without a dedicated short wavelength filter (violet) or some other means like the eye must have, there is no way that the camera can tell blue from violet. Both excite the same sensor. I've played around with this using blue, violet and UV LEDs.
Yes, metamerism. A big deal in the print industry. We actually had some very cool little stickers that would show stripes if viewed under non standard lighting. They warned that if you see the stripes, lightening is not standard. Ever see those?
It sure is!
It's a little bit more complicated than just the difference between additive and subtractive colours.
Not that what you have said is untrue, but you can have a spectral colour, green (coloured light), which is monochromatic, or you can achieve the same impression in the brain by the combination of blue and yellow additive metamers (monochromatic coloured lights).
CC, yes I agree. I was just trying to keep it simple. Will monochromatic blue and yellow lights combine to green? I'll have to try that.
Since there are no real yellow sensors in the eye, we must see it as green and red sensors both lit up.
Since there are no real yellow sensors in the eye, we must see it as green and red sensors both lit up.
They actually produce light (as I understand it) and so appear much brighter than ordinary pigments - because they really are brighter. They don't just absorb, they also produce light. Or at least convert UV to some visible wavelength. It's a pretty cool trick.
Exactly. That means "fooling imagination" as if the color is monochromatic. That's why it s so difficult to fool imagination completely by capturing and reproducing using selective electronic devices. And that's why incandescent lamps will be always preferable for health and arts than artificial lighting that re-creates as if white light by few narrow strips.
They do that just fine. I have a nice Christmas light string made by GE, I bought it in Costco. It does that just fine. Like my Epson projector that I use to watch movies.
But it does not mean that LED lights completely replace incandescent lamps
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