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Comment Optical engineering explanation for purple fringe (Score 1) 472

The purple fringe problem is an old one when it comes to digital cameras. Most famously this spoiled the production models of the Sony DSC-F828 in 2004, which was supposed to be the ultimate high-resolution digital camera in its day with perfectly optimized Zeiss optics. The irony was that the very quality that made the lens superb in visible light made it that much more aberrant in infrared. Infrared blocking filters are not perfect, so out-of-focus infrared images appear whenever there is extreme contrast in the scene at extreme off-axis angles.

Purple fringes like this are not due to lens coatings or sapphire windows. Nor are they due to lens flare, flare being due to internal surface reflections, so it is wrong to call it a purple flare. Strictly speaking, it is a chromatic aberration, compounded with some coma effects.

The cause is simply infrared (IR) light being imaged by the image sensor. The lens is highly corrected to sharply focus visible light, but such corrections result in severe aberrations in focus for for any light outside the visible. These aberrations worsen with wider angles, that is, the farther out toward the edge.

Of course there is an IR blocking filter in the lens, but it is not perfect. A very small proportion of the IR does get through, but not enough to normally be imaged. However, when you have an severely bright highlight in the scene that is overexposed on the edge of the frame, the light itself will be "blown out" (pixels all white), but abberant unfocused IR rays will form a fringe. This fringe is purple because that is the false color that IR light yields in an RGB sensor. This fringe is not blocked by the IR filter because the highlight is far more intense (potentially by huge factors) than the exposure for the rest of the scene, so even 99.99 percent IR blocking filter lets through enough rays that when aberrated show up as a bright fringe.

Example from a Sony DSC-F828. Note the camera flash reflections from the shiny trophy at the edge of the frame have purple fringes, while the reflection off the glass near the center of the frame does not.

This problem only appears when you have a highly corrected lens, a high-resolution sensor, a high-speed-wide-angle lens, less-than-perfect IR filtering, and a scene of high spatial contrast at the edges. That's why it doesn't appear in most cameras, because few cameras are so high-performance in all of those areas at once.

Fixing the problem can be done by reducing the performance in one or more of those areas. Or you can design even better optics, but that is difficult to implement in a compact size like a phone requires, because it takes bigger bits of glass and more of them. You can also correct in firmware or software.

Comment Re:new owner may need to honour preexisting contra (Score 1) 443

No, not at all. Buyouts are structured typically to buy *assets* only (including the trade name), not obligations (debts, contractual obligations, etc). Warranties go extinct in such cases. No knowledgeable businessman would buy a whole business in the sense of buying into potentially unlimited liabilities. When you buy anything for a "lifetime" of support or warranty, you are only in effect buying a promissory note from a business that may or may not even exist when you come calling to collect.

Comment As a Florida homeschooling dad myself ... (Score 1) 294

I have to chuckle at reports like this, because I'm often told my homeschooled kids are not in the "real world" and aren't being properly "socialized".

Why would any child or parent object to fingerprinting?

Coercion and regimentation in government schools is just the *real world*, to wit:

Riding buses of a kind that nobody else rides except in prison or at boot camp, painted a special DOT color that other vehicles are not allowed to use, that travel under special traffic rules that nobody else is allowed to use.

Eating food provided by the government, served in a facility with famously odd personnel, none of which would be patronized if offered to people as a free choice.

Forced to endure unwanted company that inflicts physical assaults and social harassment that would be criminal or tortious if acted by adults.

Required to submit to government employees who are 100 percent unionized and paid twice what they're worth in the free market, who work 3/4 of each day for 3/4 of the year. (For those of you who learned public school math, that's 3/4 x 3/4 = 9/16, or about a half time job for double a full time annual wage.)


The real world?

Comment This story repeats a stupid fallacy (Score 1) 330

"... white light is a mixture of colored rays that can be recombined with a lens".

White light splits into colors because of dispersion in the prism. Passing dispersed rays through another prism just disperses them more, it does not recombine them. This fallacy is famously repeated in public school science textbook diagrams of paired prisms. Newton never performed any such demonstration. He was able to demonstrate recombination in Opticks, but with something much more complicated than a pair of prisms.

Comment "Neutrality" is a phony, lying term (Score 1) 702

"Net neutrality" consists of government force applied to private entities to coerce certain behavior that would not occur freely.

Like any government "regulation", as the liberal fantasy wants to label all such schemes, ultimately it comes down to, "you and your network assets do what we say, not as you like, or men with guns will come and make you."

Comment Repeat after me (Score 1) 117

Beware the "radiant heat" fallacy.

The solar flux consists of electromagnetic radiation. Electromagnetic radiation is not heat. The sun does not radiate heat.

This novelty looks remarkably like just adding a thermocouple, which has never been any good at turning heat into electricity.

Comment Absurd (Score 1) 316

That's a ridiculous cost of 12 euros per watt, which is about 100 times the cost of a conventional power plant.

5 MW times 10 hours/day (?) is worth about 2500 euros/day wholesale.

So basically you have invested EU 60 million to earn EU 2500 per day, for a gross ROI of 1.5 percent, before expenses and depreciation.

Which is to say, this thing will have earned back its carbon cost in about 100 years.

This must be a very durable plant, what with the MOLTEN SODIUM CHLORIDE and all.

Environmentalism: expensive, shoddy, deadly [Schwartz].

Comment Re:I have a big problem with everything (Score 1) 952

... Even in my living room, watching a Bluray at 1080p, I still see the pixels from 10-12 feet away on the couch.


Human visual acuity resolves about 1 minute of arc. 1080p on a 55 inch HDTV is about 40 pixels/inch, which is about 40 seconds of arc per pixel from 10 feet away.

You might be seeing coarser pixelation such as compression artifacts, but not the actual pixels.

Comment My simple interview question. (Score 1) 441

I ask how you would solve Jumble puzzles from the newspaper, given a vocabulary text file. Exhaustive search is not the answer, but given that the glut of CPU power and storage has fostered brute-force approaches to everything, this is surprisingly a quite common proposal.

The solution is quite obviously a hash lookup, but you would be surprised how few "programmers" come up with that.

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