How to Beat a Speeding Ticket for Motorists

[flatmaster]

When I hear "mathematical, but used by artists", I think "Fractal" or "Tessellation" but neither of thoes seems to fit.

My guess is that "over the shoulder" refers to a specific camera angle where the camera is looking over one of the character's shoulders and we see what they may be seeing.

 

[collinsmark]

When I hear "mathematical, but used by artists", I think "Fractal" or "Tessellation" but neither of thoes seems to fit.

Nope. Neither fractals nor tesselation is involved. (The art of which I speak predates modern computers.)

"The shoulder" almost always involves a different, particular mathematical function though. Here's a hint. Before the advent of electronic calculators this mathematical function was used pretty commonly by most anybody doing numerical math. So even non-technically minded, professional artists would probably be at least somewhat familiar with its use.

My guess is that "over the shoulder" refers to a specific camera angle where the camera is looking over one of the character's shoulders and we see what they may be seeing.

Sorry, but that's not the same "over the shoulder" to which I refer. My "shoulder" does not actually involve a human shoulder.

That said, you're really close to the correct subject matter.

Here's another hint: The aspect of the art that's dying fast (or is arguably already dead) has only been doing so for maybe a decade or two (I'd say closer to a decade and a half, but its hard to pin down).

 

[flatmaster]

Maby shoulder refers to a step function. The art application would be a film camera that must move film step-wise rather than continuously. If something is "over the shoulder" the film is out of synch with the shutter and you see two halves of a cell rather than a single cell.

 

[Office_Shredder]

Over the shoulder is when you expose a picture for too long?

 

[collinsmark]

Over the shoulder is when you expose a picture for too long?

Correct. And I suppose that that's close enough that I'll give the complete answer.

Photographers used to pick the film they were going to use for a shoot based on the film's "Density vs. log E" characteristics.

The curve used to look similar to this one,

found in this link.
http://en.wikipedia.org/wiki/Sensitometry

Any photographer worth his or her weight used to know about H-D curves. The top part of the curve is known as "the shoulder" where overexposure compresses the details of any highlights. The opposite of the shoulder is "the toe" and any exposure in this region compressed details of the shadows, and was called "under the toe."

If a photographer makes an exposure mistake using film, he/she could often get some of the detail back in the darkroom print, but often at the expense of contrast. That said, photographers such as Ansel Adams characterized all his film and equipment to the point where he chose the ideal equipment for the particular scene, such that the exposure extended all the way from toe to the shoulder without any significant saturation -- making the very most of the equipment. He didn't stop there either. The same attention to detail was done with his darkroom.

Today though, photography is changing. CMOS and CCD, electronic sensors usually have a different shaped curve. The linear region of the curve typically extends all the way up to the top where it sharply plateaus. Photographers rarely call exposure in this plateau region "over the shoulder" anymore, since there isn't even really a shoulder. Instead they're just called "blown highlights." And once they're blown, they're blown. There ain't any amount of Photoshop that will get them back (without faking it).

On the other end, electronic sensors don't have a toe either. The linear region just keeps going down and down forever, or until it's just random noise. This makes digital sensors well suited for astrophotography where long exposures in low light situations are the norm.

Okay Office_Shredder, your move.

 

[Office_Shredder]

Lensing

As you might guess it has to do with focusing light. But this particular form of lensing can be quite problematic for solar power enthusiasts

 

[flatmaster]

I suppose this is the type of lensing that occurs with water droplets on the panel. A dry panel would have even lunumous flux over it's entire area, but a panel covered in water droplets would experience pin points of high intensity light caused by lensing from water droplets. I suppose this light may be intense enough to damage this part of the solar array.

 

[Office_Shredder]

Water droplets can indeed be the cause of this lensing, but not when placed on the array. In fact in certain applications solar arrays are sprayed with water to cool them off - this helps to increase their efficiency

 

[Office_Shredder]

A hint: If you can see this lensing, it will usually pass you by quite quickly

 

[Office_Shredder]

And the weatherman can tell you whether you should expect to see any

 

[collinsmark]

Okay, I'll bite with a nearly wild guess. (It's been about a day with no guesses, so I'll give it a go.)

Even the dry atmosphere can refract light. And this is called atmospheric lensing.

When looking at the sun at sunset or sunrise, you're not actually looking toward the true position of the sun at the time. The direction to the sun is actually lower than it looks. This is because the atmosphere bends the sunlight "down" (so to speak) making the direction to the sun appear farther up.

If you have a simple photovoltaic panel (PVP) and you want to get maximum efficiency, its best to make the PVP's surface normal to the direction of the sunlight. For most situations, this is easy enough by mounting the PVP on a equatorial mount, and have it track the Earth's rotation using a simple timer.

But such a setup would not be as efficient as it otherwise could be around sunrise or sunset due to the fact that the sunlight is not coming from the true direction of the sun, because of atmospheric lensing. That's not a big deal though. All that is lost is a little efficiency.

But wait, it gets weirder. Potentially a lot weirder.

Depending on the weather conditions anywhere between your location and down past the horizon, this effect can be less or more pronounced such as discussed in this link (The sun has already set, and yet then there's another sun! WTF?):

http://www.spaceweather.com/gallery/indiv_upload.php?upload_id=37810

It doesn't end there either. Many of you have probably seen a mirage at some time or another. A mirage can be considered another form of [atmospheric] lensing. When air is warmed by a hot surface, it can bend the light up making an additional image of the sun* (or sky or whatnot), seemingly coming from a pool of water (or mirror) on the ground (where no pool of water or mirror exists).

*(Edit: the actual scenario where an additional image is of the sun itself is not likely to happen from a hot ground mirage, since the ground usually starts cooling off by sunset. But I'm just saying that the atmospheric lensing in the first link is not altogether different than a mirage.)

So how can this be problematic for a solar power enthusiast?** Well, there are more ways to harness solar power than a simple PVP.

One of them is concentrated photovoltaics

http://en.wikipedia.org/wiki/Concentrated_photovoltaics​

And there's also concentrated solar thermal.

http://en.wikipedia.org/wiki/Concentrated_solar_power​

Both of these methods require proper tracking of the sunlight.

Improper tracking of the sunlight, combined with concentrating that light, can cause bad things to happen. Very bad things: things such as awful fires, melting metal/concrete etc. There's going to be a focused beam of sunlight somewhere, so you'd better darn well make sure that it lands on something you want it to, and goodness sake not on something you don't want it to.

But what if (due to atmospheric lensing) there are suddenly two suns? Now that's a problem!

That's my guess anyway.

**(Edit: And even for a single non-concentrated PV system, such atmospheric lensing might throw off an automatic feedback sunlight tracking system, if the mount contains such a feedback tracking system. No actual danger in this situations, but I imagine it could completely throw off the mount's tracking abilities for awhile.)

 

[Office_Shredder]

collins, that's a pretty awesome answer but unfortunately wasn't the one I was thinking of My lensing is a bit more of a mundane process that's named after the meteorological phenomenon that spawns it.

It's pretty hard to find on google, I highly recommend using quotation marks when searching

 

[lisab]

Is it related to rainbows?

 

[OCR]

Sun dog??

http://en.wikipedia.org/wiki/Sun_dog



OCR

 

[Office_Shredder]

Sun dogs and rainbows are both tangentially related to the lensing I am referring to, in that they are caused by refraction of light through water in the atmosphere, and so is this effect. This lensing often requires a more noticeable concentration of water to occur though.

(Also sun dogs may have a similar effect on solar power as this lensing but I'm not sure about that so take it with a grain of salt)

 

[OCR]

requires a more noticeable concentration of water

Haar, haar, haar... lol



OCR

 

[OCR]

Ignore the ignorant guess at post # 196...
OCR... lolhttp://en.wikipedia.org/wiki/Haar_(fog)

 

[Office_Shredder]

If that haar was located a couple miles in the sky it might be perfect :p

 

[flatmaster]

Lensing from clouds? I thought cloud droplets were small enough to cause scattering rather than refraction.

 

[flatmaster]

Every cloud has a silver lining

http://en.wikipedia.org/wiki/Silver_lining_(idiom )

 

[collinsmark]

By golly, I think flatmaster got it!

Cloud lensing is a term used by solar power system owners to describe a spike in the generated solar power of a photovoltaic (PV) system that happens for a few seconds after a cumulus cloud passes in front of the sun. It's enough to sometimes cause the output of the PV panel to output over its rated capacity (which otherwise would pretty much never happen).

The actual physics behind the phenomenon is questionable, at least in my mind. Here are a couple of hypotheses I've found from various solar power forums on the Inner-webs.

1. The water droplets in the cloud, or atmosphere around the cloud, somehow focus the sunlight like a lens via refraction, thus increasing the light intensity at the location of the solar PV system. Personally, I kind of doubt this one. I'd like to see more evidence before believing this.
2. The light reflects off the edge of the cloud in a highly directional manner. [Edit: not necessarily when the cloud is directly obstructing the sun, but rather when the cloud is very close.] For a few seconds, the solar panel "sees" not only the direct sunlight and any residual skylight, but also (additionally) a very, very bright edge of the cloud. This one sounds more reasonable to me.

Regardless of the true cause, a passing cloud can cause the power of a PV panel to increase momentarily. And solar power enthusiasts do call this "cloud lensing." And I suppose that somehow or another it is the same thing as flatmaster's "silver lining" post.

Also, just before the cloud passing finishes, the PV system is in the shade and cool. As Office_Shredder has mentioned, cooler PV panels are more efficient. So this is another contributing factor. Put together, the overall effect might boost the energy output of the cell by perhaps 30% (compared to a clear sky, and all else being equal), but just for a few seconds.

Why would this cause problems with a PV system? Well, the PV panels are attached to an inverter with its own rated capacity. Putting too much current into the inverter could cause it to clip its output waveform (not good) or worse, cause it to shut down the whole system (not good at all).

Office_Shredder can confirm if I'm correct or not about flatmaster winning the round.

 

[Office_Shredder]

collins, you've described it spot on. You can actually see cloud lensing - when the cloud is poking out from a cloud it's distinctly brighter.

 

[collinsmark]

collins, you've described it spot on. You can actually see cloud lensing - when the cloud is poking out from a cloud it's distinctly brighter.

Okay, but I think it's flatmaster's round. I did some search engine research, but it was flatmaster who first brought up clouds and the sunlight passing near their edges.

 

[collinsmark]

flatmaster?

 

[flatmaster]

Ok. The new word is "chain whip".

Hint: it's not a weapon.

 

[flatmaster]

A chain whip is in fact a tool rather than a weapon. If you saw one and didn't know what it was, you may guess that a chain whip is a weapon.

 

[Jonathan Scott]

Well, I think I know what it is from helping reassemble parts of a bicycle wheel long ago (and Googling seems to confirm it) but I don't have any ideas for new jargon.

 

[flatmaster]

That's right. Can't really grab onto a sprocket with a regular wrench, so a chain whip is needed. Your go Scott

 

[Jonathan Scott]

Wikipedia says that what I know as a "chain whip" is apparently called a "strap wrench" elsewhere.

OK, this time, it's a pair of verbs: huff and puff

 

[Office_Shredder]

It's a method of steam injection used in oil wells - you inject steam to heat up the oil in a well, then let the natural rise in pressure force the oil out (or something like that)