Incandescent/halogen ban?

[Helge]

The eye's cones on the retina only perceive red, blue and green. Other colors transmit frequency signals to more than one cone. The brain then processes them to come up with another stimulation in the brain to reporesent the other unseen color. But the brain really doesn't :see" those colors as they are in the natural world. So how one perceives color can be different from one person to another.

Maybe the whole universe is all perception in our brains. The universe really doesn't exist like we imagine it which is why we really can't understand it. It;s like gravity which is not a force as was originally believed. Its now said that it's curvature of the universe. Well explain that? Explain color. Explain the color purple to a blind person.

That is not even an oversimplification.

 

[Don_ih]

So how one perceives color can be different from one person to another.

That has no bearing on how one kind of light impacts perception of colour vs another kind of light.

Furthermore, that kind of discontinuity is not only impossible to prove or disprove, it ultimately would not matter, since the referent of one person's "red apple" would match the referent of another person's "red apple". It's only in the instance of a demonstrable anomaly (red/green colour blindness, for instance) would any of that matter - and you will notice that, in that case, the referents do not necessarily match. A person with severe red/green colour blindness may not call a red apple "red".

 

[Alan Edward Klein]

Why We Don't See the Same Colors​

"We sometimes think of colors as objective properties of objects, much like shape or volume. But research has found that we experience colors differently, depending on gender, national origin, ethnicity, geographical location, and what language we speak. In other words, there is nothing objective about colors."

Why We Don't See the Same Colors

What I see as red you may see as orange.

www.psychologytoday.com

 

[Alan Edward Klein]

That is not even an oversimplification.

What do you mean?

 

[Alan Edward Klein]

That has no bearing on how one kind of light impacts perception of colour vs another kind of light.

Furthermore, that kind of discontinuity is not only impossible to prove or disprove, it ultimately would not matter, since the referent of one person's "red apple" would match the referent of another person's "red apple". It's only in the instance of a demonstrable anomaly (red/green colour blindness, for instance) would any of that matter - and you will notice that, in that case, the referents do not necessarily match. A person with severe red/green colour blindness may not call a red apple "red".

Perception is just different nerves in our brain being stimulated. When we see something that matches the stimulation that we identify it as a color or object that we "saw" from before. But the stimulation in our brain does not match the actual reality of the object, color, etc. Who knows what it actually is in reality? It's all one huge construct in our brains. That's why we can't explain consciousness. It's why we can't explain the color purple to a blind person becasue they never experienced it to construct it in their brains. It;s an experience that is internal as stimulation to certain nerves in the brain. But that has nothing to do with actual color frequencies shot off when light hits the object. It's only purple in our brains.

 

[DREW WILEY]

Nobody sees the same color the same way except briefly, even under the same light. Things like simultaneous contrast, successive contrast, and metamerism kick in. You don't need to be a neuroscientist or ophthamologist to know that. VanGogh intuitively understood it better than any of us. And every highly skilled house painter I knew understand it better than 99% of the color photographers I ever met. Back to the basics. Gets a good little handbook on color theory like Itten's, The Elements of Color.

What CRI is good for is shopping for the best bulb to evaluate your results, that is, if you're shrewd enough not to believe a thing printed on any bulb package in a typical consumer store. Good bulbs cost a lot more and come from specialty sources. Around here this time of year we have enveloping white coastal fog which acts like a natural softbox, excellent for evaluating colors.

 

[Alan Edward Klein]

Nobody sees the same color the same way except briefly, even under the same light. Things like simultaneous contrast, successive contrast, and metamerism kick in. You don't need to be a neuroscientist or ophthamologist to know that. VanGogh intuitively understood it better than any of us. And every highly skilled house painter I knew understand it better than 99% of the color photographers I ever met. Back to the basics. Gets a good little handbook on color theory like Itten's, The Elements of Color.

What CRI is good for is shopping for the best bulb to evaluate your results, that is, if you're shrewd enough not to believe a thing printed on any bulb package in a typical consumer store. Good bulbs cost a lot more and come from specialty sources. Around here this time of year we have enveloping white coastal fog which acts like a natural softbox, excellent for evaluating colors.

I'm going nuts trying to find a replacement for my high hat floods in my kitchen. I installed nine of the same type when LEDs came out, Now one has gone bad. The same replacement is no longer available. Trying to find one that matches the color in lumens, CRI, wattage, etc is really difficult. Then when you finally find one, it delays on startup and shutoff unlike the originals.

 

[DREW WILEY]

Alan - I got my display wall and framing room screw-in LED floods from Waveform Lighting. Solidly built, true architectural quality bulbs, even better packaged for shipment. You buy directly from them. Their website explains the issues you are asking about, and they even have advanced models of CRI which cover some of the loopholes, so to speak, in the traditional classification system. I chose 5000K ones, but there are other color temp choices. Way better color rendition than bulbs you get in ordinary stores. Instant on and off.

If your bulbs have an afterglow, it means they contain phosphors and are CFL variety, and not LED. CFL's represent an interim technology, and are mostly trash. I have boxes full of them, given to me for free, but hesitate to use those for anything other than temporarily lighting some remote corner of the shop. They give me eyestrain anyway - horrible spectral qualities.

 

[Sal Santamaura]

...If your bulbs have an afterglow, it means they contain phosphors and are CFL variety, and not LED...

Quality LED bulbs are not "instant off." They take a few moments to fade after line voltage is removed. That's a result of their DC power supply capacitors bleeding down.

 

[koraks]

Quality LED bulbs are not "instant off." They take a few moments to fade after line voltage is removed. That's a result of their DC power supply capacitors bleeding down.

There's no correlation between the quality of the light and the driving circuitry in terms of buffering capacitance, at least to the extent that it gives a perceptible afterglow. Most modern LEDs will have barely any capacitance given the fact that bulk capacitance requires electrolytics that form a failure point, plus they cost money and take up precious space.

What Drew says about the phosphors is correct btw in that these are sometimes also responsible for the afterglow.

As such, it can't be said that 'quality' bulbs will have more or less after-glow than lesser quality bulbs.

If your bulbs have an afterglow, it means they contain phosphors and are CFL variety, and not LED.

White LEDs virtually all use phosphors for spectrum shaping, save for a few types leftover from the very early days that are R, G, B emitters and highly discontinuous as a result. The latter are unlikely to be encountered in the shop shelves at this point. There's no such thing as a white LED emitter. A LED emitter always produces a narrow peak due to the semiconductor used having one specific bandgap. Different color emitters can be made by tailoring the semiconductor chemistry to the desired bandgap and therefore emitted wavelength. For wide-spectrum light, a phosphor is required to convert this narrow wavelength into a broader spectrum. In that sense there's a very clear parallel between CFL's and white LEDs. How different or similar the phosphors between the two are, I don't know; never looked into that aspect.

 

[DREW WILEY]

I know the difference just by flicking a light switch. I don't pretend to be an engineer. Even with overhead fluorescent tubes, my old high-quality US-made GE ones lose their afterglow way way faster than the Sylvania or Phillips made-in-China substitutes, falsely claiming to also be 5000K, high CRI. And I'm stating "instant" in terms or my own perception. If they're completely off by the time it takes me to walk a few steps and fetch a piece of paper or film out of a paper safe, that's plenty fast for my purposes. I'm not referring to using LED sources in enlargers or other exposure systems. And I already mentioned the brand of LED room lighting floodlamps I'm using, which aren't cheap. About $30 apiece, and intended for color evaluation, art display purposes, and reducing eyestrain.

Another factor to consider is that CFL's were never fined-tuned and blended to the level that high-end fluorescent tubes were. They instantly gravitated into cheap consumer goods marketed as simulating "warm white" or "daylight", or whatever the BS marketing coefficient wanted people to think. Rarely were tested spectrograms published like with professional lighting, and like with
better LED lighting today. CFL bulbs barely reached their adolescent ugliness, and might not ever get beyond it. It's an interim low-E technology doomed by advances in LED options.

But this takes me back to a previous discussion, Koraks, about LED printing devices. I looked certain things up to jog my memory. The ZBE Chromira system is based on R&D at least 40 years old, involving a type of proprietary LED technology predating the kinds of off the shelf LED component options someone would choose from today if trying to make an LED enlarger head. Chromira printers are still being made today, but perhaps a little differently configured from the early ones.

I don't want to derail this present thread, but I am tempted to try the new Fuji Super C II version, which is now available in a full range of roll sizes in this country. But it's almost impossible to tell from their own literature exactly why it's "digital only". Too steep a dropoff into DMax in their opinion? - that would be an advantage to me. Different recip failure threshold than previous dual-usage
Super C? - no big deal. Doesn't dev full DMax without their own special RA4 tweak? I develop in drums, so can accommodate different time/temp variables as needed, or simply buy their own chemistry. Might need supplementary contrast masking? I can almost do that in my sleep. Maybe NOBODY has a correct PRACTICAL answer yet because it is such a small overall niche to them.

But if I have to drop two or three hundred dollars to find out the truth, well, that just comes with the territory of color printing. I've lost a lot more on other experiments. And I presume the DPii paper is lower contrast than Commercial Super C etc; but that's not available in the gloss surface I need. Somebody has to brave sailing past the Pillars of Hercules. And I've got a lot of good negs which just don't look right on the Supergloss finish I'm currently using; but those that do - Wow! It's a superb product for optical enlargements. Gotta process another big one in a few minutes. I exposed it earlier.

 

[koraks]

I don't want to derail this present thread

Good. Please don't.

 

[Helge]

What do you mean?

Exactly what I wrote.
The L M and S cones in the retina for starters doesn’t even corrosbond with traditional RGB. The distribution of the cones and processing in the retina of their output to arrive at a “colour” is another highly complex and not fully understood matter.
Then there is the “horizontal” cells that work as inhibitors to raise contrast.
There is the photosensitive retinal ganglion cells that senses blue and deep blue.
Rod receptors is also discovered to play a part in daylight vision to an increasing degree with new research.

 

[Sal Santamaura]

...it can't be said that 'quality' bulbs will have more or less after-glow than lesser quality bulbs...

Sure it can be. I said it. The size of power supply capacitors in higher quality bulbs is larger than cheaply made ones. Were phosphor afterglow to be the reason for LEDs taking a few moments to fade when line ("mains" for Europeans) power is removed, they'd be just as dangerous to photosensitive materials as fluorescent bulbs are, i.e. one would need to wait several minutes before exposing film or paper in their presence. One doesn't need to worry about that. As soon as LEDs have visually faded to "black" (normally a bit more than one second for good ones), all's well in the darkroom. And that's despite their high lumen output and there being no opportunity in such a brief period for the viewer's eyes to dark adapt.

 

[Helge]

[this may be far OT -- not even close to bans and workarounds. MODS Please, do what you consider best]
The making of color using 3 colorants can/is described by something like this:View attachment 340336
the main point of this is that the color of point T may be formed in many ways.
[this is only of practical value for those who "make" their own assembly system]

Bravo for digging out that graphic. Illustrates well one of the problems with CRI and related standards.

 

[DREW WILEY]

That kind of color mapping goes back to the 1920's. And to plot colorants you need a three dimensional model. Transparent or backlit media use a 3-axis model, opaque colorants like paint of inkjet media, a 4-axis model (with the white tone axis leading directly opposite a separate tint axis going toward black). How it's all modernized is by computerizing the details via analytic geometry programs. It's original practical application would have simple CMYK printing applications measured through basic tricolor filters. The emergence of sophisticated spectrophotometers plotting many many points changed all that.

The gamut of human vision itself cannot be reliably plotted in that manner because it's not a constant. It's something physiologically interactive; and our cones fatigue very quickly. Just stare at an intense color for a few moments and then close your eyes. What do you see with your eyes closed? Typically the complementary color - the exact opposite. Your fatigued cones are trying to refresh themselves, and reset the balance.

 

[Helge]

That kind of color mapping goes back to the 1920's. And to plot colorants you need a three dimensional model. Transparent or backlit media using a 3-axis model, opaque colorants like paint of inkjet media, a 4-axis model (with tone vs tint plotted separately). How it's all modernized is by computerizing the details via analytic geometry programs.

Just CIE 1931 color space. The great thing is the captions and lines pointing to “T”.

 

[DREW WILEY]

Now certain folks have programs where they can rotate and peer into that 3-d color space on their screens as if it were a literal transparent object. But I had enough of it working with industrial pigments, and do zero inkjet printing, so can forget about all of it today and just drive to the beach and see with my own eyes how the flowers are blooming. Just waiting for the morning commute traffic to clear up across the Bridge. And like I hinted earlier, there's nothing quite like soft white enveloping coastal fog for rendering colors. Better than any artificial light source I can think of.

 

[koraks]

The size of power supply capacitors in higher quality bulbs is larger than cheaply made ones.

Not really. There's no quality gain in larger caps beyond a certain point and that point is reached far before noticeable fading/dimming is reached. After all, only half a 50Hz or 60Hz phase needs to be bridged, assuming a still fairly common topology where a string of LEDs is put in series and fed with switched (a few hundrerd kHz typically) HVDC taken from a small buffer cap that's fed through a bridge rectifier. Hence, whatever capacitance is present is not dictated by 'higher quality' of the bulb, but by driver topology and required output power. If you define 'high quality' along the lines of things like low flicker, dimmable, high CRI etc. you'll find there's no relationship between those qualities and the size of a buffer cap.

Were phosphor afterglow to be the reason for LEDs taking a few moments to fade when line ("mains" for Europeans) power is removed, they'd be just as dangerous to photosensitive materials as fluorescent bulbs are

In the case of certain bulbs this is absolutely the case.

 

[Sal Santamaura]

...The size of power supply capacitors in higher quality bulbs is larger than cheaply made ones...

Not really. There's no quality gain in larger caps beyond a certain point and that point is reached far before noticeable fading/dimming is reached...

You confuse correlation with causation. I didn't say the larger caps were what made better LED bulbs high quality. Higher quality LED bulbs tend to use larger capacitors.

...Were phosphor afterglow to be the reason for LEDs taking a few moments to fade when line ("mains" for Europeans) power is removed, they'd be just as dangerous to photosensitive materials as fluorescent bulbs are...

Perhaps very low quality LED bulbs that depend excessively on phosphors to avoid artifacts might. I've never sought or used those. None of the high-quality LED bulbs I've installed over more than half a decade have any actinic effect after approximately one second. Moral of the story: avoid junk.

 

[faberryman]

Perhaps very low quality LED bulbs that depend excessively on phosphors to avoid artifacts might. I've never sought or used those. None of the high-quality LED bulbs I've installed over more than half a decade have any actinic effect after approximately one second. Moral of the story: avoid junk.

How do you avoid junk LEDs? Do LED manufacturers specify the amount of phosphors they depend on to avoid artifacts, or the length of the "actinic effect"? I buy my LEDs for around the house at Home Depot. They seem to turn off and on instantaneously.

In my darkroom I still use tungsten bulbs because they haven't needed replacing for a couple of years. Beside, they are only on when I am either setting up or cleaning up, except when I want to look briefly at a print in the wash. The rest of the time they are off. If they were LEDs, and they took a few seconds to go completely off, it wouldn't make any difference in my workflow.

If you are making color prints, and evaluating them in the darkroom, you would want a bulb with a reasonably accurate color temperature for whatever presentation color temperature you have decided to print for. For example, the bulbs Drew mentioned come in 2700K, 3000K, 4000K, 5000K, and 6500K versions, all +/- 100K. However, it shouldn't matter how long they take to turn on or off.

Did we worry about on/off times with tungsten bulbs, CFL bulbs, or fluorescent tubes? This thread is the first I have heard of it.

 

[DREW WILEY]

Home Cheapo specializes in substandard products, just like WalMart. In fact, it's Cheapo Depot that predominantly led to GE stopping bulb manufacture entirely. Even formerly reputable product lines are expected to cheapify and outsource what is sold in there. There are some exceptions of course. But their outright policy is often to outright bankrupt manufacturers, buy out the brand label, and then outsource it to a bait-and-switch much lower quality product line. Same with WalMart. I could cite many many blatant examples of that; but this is not the right venue for that. The kind of light bulbs you find in any kind of chain store is likely to be substandard these days, and made in China. It's not just about instant this or instant that. It's about overall build quality too.
Chain stores demand lowest-bidder products. That's how it works. I could state, "You get what you pay for"; but really, it's more like, "You get what they were willing to pay for." ... if they even paid for it at all. Sometimes they only remit the supplier from what they actually sell, and charge them warehouse storage "rent" for what they don't. Some products never do reach the store shelves because they never intended them to. Plenty of suppliers have been burned.

 

[koraks]

Perhaps very low quality LED bulbs that depend excessively on phosphors to avoid artifacts might.

Virtually all white LEDs depend completely on phosphors to make continuous light. The only exception are old, obsolete RGB ones with highly discontinuous spectra.

You confuse correlation with causation.

So your supposed correlation relies on n=...?
You must have an odd conception of engineers in assuming they throw in big, expensive and bulky caps just to look good to laypeople randomly opening up bulbs. Where I come from, they dimension components based on technical and economic requirements.

Anyway, the entire argument is pretty much moot, since a long afterglow (i.e. 'walk across the room and it's not dark yet') simply cannot be caused by a buffer cap in a typical light bulb. In a typical E27 fitting, you could squeeze at the very most a 10cc cap or so, which translates into maybe 25J of stored energy. This is already using an unnecessarily bulky cap that no sane engineer would pick for this application. Let's assume a fairly typical 6W of output power, which translates to maybe 4 seconds of light output - but that's assuming that the cap entirely discharges into the LEDs. This doesn't happen, because the LEDs are in fact in a series string with a forward voltage of typically something like 150V and our cap also discharges exponentially. This means our hypothetical mammoth cap will drain in maybe a second to a voltage below the forward voltage of the series LED string and the LEDs will consequently be totally dark. Any afterglow beyond that point is made by phosphors. How much of an afterglow there is, depends on the phosphors used for converting the narrow--peak blue LED light to a (quasi-)continuous spectrum.

Presently, there is no market-ripe technology that can create decent quality (CRI>90 or so) white LED light without the use of a phosphor. This, combined with the restraints of package sizes and physics as outlined above, dictates that any afterglow longer than a few hundred milliseconds (at most, in practice) will be due to the phosphors used.

So, having said that, please do go on with the discussion on what LEDs are or aren't junk, whether CRI is a decent measure for light quality etc.

 

[Sal Santamaura]

How do you avoid junk LEDs?...

When I re-lamped the house around six years ago, I evaluated what was available by reviewing specifications and customer reviews that addressed failure rates. I eliminated cheap stuff. It seems to have worked, since not a single bulb has failed since.

...Do LED manufacturers specify the amount of phosphors they depend on to avoid artifacts, or the length of the "actinic effect"?...

Not that I'm aware of.

...I buy my LEDs for around the house at Home Depot. They seem to turn off and on instantaneously...

The Euri brand bulbs I installed (3000k, 90+ CRI) are not shown as available at Home Depot. They have a perceptible, but rather short -- I'd estimate it at around 250 milliseconds -- turn on delay. They take approximately 1-1/2 seconds to fade when turned off.

...If you are making color prints, and evaluating them in the darkroom, you would want a bulb with a reasonably accurate color temperature for whatever presentation color temperature you have decided to print for...

I've never made color prints in the darkroom and don't intend to. You are correct inasmuch as, if color prints were intended to be viewed in a home illuminated by LED bulbs, the same LED bulbs ought be used in the darkroom to evaluate them.

...Did we worry about on/off times with tungsten bulbs, CFL bulbs, or fluorescent tubes? This thread is the first I have heard of it.

Never with tungsten, although for very short exposures in an enlarger, the time it takes for a filament to stop glowing can effect print density. With CFL and fluorescent tubes, the phosphors could glow for as long as several minutes, definitely something that was "worried about" by those who understood things.

Virtually all white LEDs depend completely on phosphors to make continuous light...

You address continuous spectrum while I refer to continuous intensity.

...You must have an odd conception of engineers

I spent my entire career around engineers. I are one. My conception of them is based on experience.

...the entire argument is pretty much moot, since a long afterglow (i.e. 'walk across the room and it's not dark yet') simply cannot be caused by a buffer cap in a typical light bulb...

Which is why I never posited any such afterglow duration. As mentioned above, the Euri LED bulbs in my home take around 1-1/2 seconds to reach black when power is removed, and have no actinic effect after that. The ones @faberryman purchased at Home Depot he describes as turning off "instantly."

...This means our hypothetical mammoth cap will drain in maybe a second to a voltage below the forward voltage of the series LED string and the LEDs will consequently be totally dark. Any afterglow beyond that point is made by phosphors. How much of an afterglow there is, depends on the phosphors used for converting the narrow--peak blue LED light to a (quasi-)continuous spectrum...

Which is completely consistent with the fade time and lack of actinicity after it that I observe in the high-quality LED bulbs installed in my home.

...Presently, there is no market-ripe technology that can create decent quality (CRI>90 or so) white LED light without the use of a phosphor. This, combined with the restraints of package sizes and physics as outlined above, dictates that any afterglow longer than a few hundred milliseconds (at most, in practice) will be due to the phosphors used...

OK, so the capacitor holds up luminosity for one second by your analysis, but after only a few hundred milliseconds it's phosphors that are responsible. Which is it?

 

[koraks]

OK, so the capacitor holds up luminosity for one second by your analysis, but after only a few hundred milliseconds it's phosphors that are responsible. Which is it?

You're an engineer. As such, you should have no trouble figuring out the relationship between capacitance, a discharge curve and the forward voltage of an LED.

Which is completely consistent with the fade time and lack of actinicity after it that I observe in the high-quality LED bulbs installed in my home.

So your bulbs exhibit phosphor afterglow, since there's no way any engineer would actually cram a cap of that size into a bulb. Which is something you didn't realize:

They take a few moments to fade after line voltage is removed. That's a result of their DC power supply capacitors bleeding down

That was/is inaccurate. Which is what I pointed out and for some totally obscure reason you seem to have major problems with someone adding nuance to a statement of yours. Good luck with that; I'm done here.