Thursday, August 24, 2017

Intellectual humor

And now for a little intellectual humor...

For my wordie friends

For my science groupies

Any history buffs out there?

Tuesday, August 15, 2017

Seven incredible duct tape life hacks

I have assembled seven of my favorite life hacks for the guy who always has a roll of duct tape handy.

Hack #1 - Ugly mug

Let's face it. There are many of us who are just too ugly to stomach looking at ourselves in the mirror every morning. Imagine how much better you would feel if you saw Brad Pitt looking back at you? A pic of your favorite actor, a little duct tape, and you can wake up feeling sexy!

Hack #2 - Broken mirror?

Are you in the middle of seven years' bad luck? And can't scrape up the money to replace that mirror? Just duct tape your cell phone to the mirror and put it in selfie mode!

Hack #3 - Read both sides of a newspaper

A drop of oil and you can cut your newspaper reading time in half! Ok, maybe it's not duct tape, but what real man doesn't always have a can of WD40 handy?

Hack #4 - Cell phone mute

You feel a sneeze coming on. You know that your cell phone has a mute button somewhere, but don't have the time to find the manual and look it up. Grab a strip of duct tape, and viola! You got a mute button. (BTW, did you tell your wife that you are at a "convention"? You can also use this on the camera lens when you Facetime with her.)

Hack #5 - Screen dimmer

Those darn cell phones never seem to get that whole auto-brightness figgered out. Duct tape + old man sunglasses = easy reading!

Hack #6 - Can't figger out Word?

Let's face it. Microsoft Word is just too complicated! Two strips of duct tape and a piece of paper and you are word processing with the pros!

Hack #7 - Pill storage

Doncha just hate those cumbersome, ugly, hard-to-open pill boxes? A piece of duct tape and a wall is all you need to organize your pills!

Impressed? Look for my new book in quality hardware stores everywhere.

Tuesday, August 8, 2017

The brightest crayon in the shed

People are always telling me that I am not just the brightest crayon in the shed. But which crayon is?

The yellow crayon screams out "Pick Me! Pick Me!"

Well, white is the logical answer, but yellow is pretty darn close to white in terms of brightness. And a very bright yellow can also be very saturated. In this sense, yellow is kind of an anomaly in the color kingdom. All other colors, when they get saturated (color scientist use the term high chroma), get darker.

Why is yellow such a gosh darn bright color?

Munsell agrees

I am not just making up this "yellow is a bright color" thing. Munsell agrees with me, as we can see from the Munsell color pages below, where I have circled (or ellipsed in some cases) the most saturated colors on each page of constant hue.

A selection of Munsell plates with constant hue

Some preliminary stuff

I will explain why yellow is such a gosh darn bright color, but first, I need to get some fundamentals in place.

The Cohans

Those of you who are fans of my blog (I think there are currently seven of you, worldwide) will no doubt remember a stirring blog post I wrote about the cones in the eye. The image below is a recap of the exciting opening premise of that blog, suggesting that the eye has three types of color sensors, and that they are red, green, and blue.

I looked deep into her eyes,
and suddenly and inexplicably found myself hungry for H
aagen Dazs

The excitement generated at the start of the blog post was short-lived. The whole point of the post was that the colors of the cones in the eye were not quite as black-and-white as the first guess of red, green, and blue. But, if you are taking the final exam for Color Theory 101, then red, green, and blue is the correct answer. Red/green/blue is also suitable for our purposes.

Definition of eight basic colors

The RGB Cohans in the eye (not to be confused with G. M. Cohan, who was red, white, and blue) lead to a simple explanation of the eight basic colors in Color Theory 101. This is all based on a lie, but it is a useful lie. If the red cone is the only cone that sees the light, then the color we will perceive is red. Similarly, if the incoming light stimulates only the green cones, then we see green. And guess what? If it is only the blue cones, then we see blue. I bet you had already guessed that one.

How about combinations? If red and blue cones are activated (but not the green cones) then we see magenta. If the activated cones are the blue and green ones (but not the red), then we see cyan. Finally, if blue is left out and the red and green cones get all the attention, then we see yellow.

I said finally, but really I didn't mean finally, since there are two more combinations. We see black when all the cones are inactive, and white when all three are activated.

The table below summarizes the cone responses to each of the eight basic colors in the RGB color system.

Red cones?
Green cones?
Blue cones?

Oh... I forgot to mention... these eight colors are all the strongest colors. The cells in the table above that have "No" in them mean "zero light", and the ones with "Yes" in them mean full intensity. There are a zillion combinations where the amount of light captured by the three cones is somewhere between full on and full off. These are not the strongest colors.

The importance of the lightness channel

There is a famous experiment -- very famous, everyone has heard of it -- where an ace was flashed on a screen for an instant. If that instant is really small, then the subjects had no trouble identifying the object as the ace of spades. But if they slowed it down so that the ace stayed on the screen for just a little longer, people got all kinda cornfoozled. When the researcher extended the time just a bit more, then the subjects could readily understand that they were being shown a red ace of spades. (For those who did not grow up in a casino, the ace of spades is supposed to be black, not red.)

Here is a YouTube version of the red spade experiment

This dorky (but famous) little experiment sheds a little light on how our eye/brain works, more particularly on how the color signals are encoded in the neurons that connect the eye to the brain. There is one signal (carried on a neuron) which transmits our perception of brightness. 

This is a special signal. It arrives to the brain quicker than the other signals. When the red ace is flashed quickly enough, the signals that further narrow the color down to red don't make it to the brain in time for analysis. A little longer flash, and the red signal makes it, but the signal isn't stable enough for full pattern recognition. A little longer still, and the brain has time to parse the image out and understand the weirdness.

Not only does the brightness signal show up first, but it is far more important than the other signals in terms of our understanding the scene. I am old enough to remember complaining bitterly about being the absolute last family in the whole town to get a color TV. Well, maybe not the last, but my buddy, Gary, had a color TV well before we did. His father worked for Motorola. My father gave me the lame excuse that black and white were colors, so our TV was actually a color TV. It's a wonder that I can function as an adult at all, what with the extreme deprivation and subsequent emotional trauma that I was subjected to!

People leading colorful lives, despite living in a black and white world

The funny thing about B&W television is that it actually worked. I don't recall my father ever setting me down and explaining that light gray could mean the taupe uniforms of Andy and Barney, or it could mean a Caucasian skin tone, or it could mean Ethel's blond hair. Somehow, I just subconsciously understood the color transform, and never questioned it. At least until I enviously watched Gary's TV.

So, why is saturated yellow so bright?

We now have enough background to explain the enigma of bright yellow. One sentence brings it all together: the brightness signal which is fed to the brain from the eye is a combination of the signals from the red and green cones. There are two separate signals that encode 1) the difference between green cones and red cones, and 2) the difference between blue cones and green cones.

All colors that have red and green at the same intensity have the same brightness. A quick look at the table shows that white and yellow are the only colors where red and green are at full intensity.

And that is why yellow is such a bright color.

Tuesday, August 1, 2017

How do you define a color?

I got an interesting question from a good buddy of mine, Mitchell Vaughn, Well, I kinda exaggerate when I say good buddy, cuz I just met him. And it was online, so maybe it doesn't count? But, he said he liked my blog, so I think that's the foundation for a lifelong friendship. Yes. I am that vain.

Here is the question:

I hope you don't mind me asking you a question, which I imagine is a loaded question...but here it is: Are L* a* b* coordinates a color's undeniable "definition"? In other words, is there anything else that needs to be in place to define a color...mathematically speaking? I realize there are several measuring guidelines that need to be met like light source and angle, etc. but wanted to get your thoughts on this. 

Thank you, Mitchell

I have three answers, the first one simple and theoretical, the second one complicated and theoretical, and the third one practical.

Quick answer

Color is properly defined as a sensation inside our head. So, once we have defined the relative amounts of light that the three cones in the eye will see, the color has been defined. Well, almost. The eye, brain, and the glop in between need a reference point to establish what white is. All color understanding in the brain is compared against this white reference. But since you're talking about L*a*b* values, this has already been mixed into the soup.

Sealab stew is a hearty meal all by itself!

So, the first answer is that, yes, an L*a*b* value defines a color, provided you know what white is.

Necessary qualifications

But when we are talking about L*a*b*, we are almost always talking about the color of objects -- be it the ink on a package, the paint on a wall, or the color of a plastic part. And (OK, this is gonna sound weird) objects don't have colors.

Consider the red ace of hearts. What color is the heart? Red, of course.

I took three pictures of two aces below. The camera and cards were not moved, all I did was change the lighting. Honest to god... there was no Photoshopping in the images below. No special tricks, other than playing with the lighting.

What color is the ace of hearts?

In the image at the left, taken with "normal" lighting, we see "normal" colors. The heart on the ace of hearts is red. For the middle image, I turned off all the lights in the room and illuminated the cards only with a 456 nm blue LED. The color of the red ace of hearts is now pretty much the same as the ace of clubs; it's black.

The right-most image shows what happened when I swapped in a 626 nm red LED instead of the blue LED. Now the color of the red ace of hearts is white. Or maybe it's red?  I dunno how you would explain it. True statement: The color of the red heart is nearly the same as the color of the card stock. Subjective statements: If you call the card stock white, then the heart is white. If you call the card stock red, then the heart is also red.

I will pause while you consider the implications of this. The color of the heart depends on whether your brain has decided that the card stock is white or red.

This is an extreme example, but all objects, to a greater or lesser extent, will change color as the spectral characteristics of the light changes. I might add, two colors may match under one illumination, but not under another. The ace of hearts matches the ace of clubs at the blue light club, but matches the card stock in the red light district. My wife loves to say the word for that: metamerism. She is not all that fond of saying red light district, or any of the other words for that.

To define the color of an object, we need to specify the spectral characteristics of the light that hits the sample. 

To make matters worse, the amount and spectral composition of light that reflects from an object depends to a greater or lesser extent on the angle that the light hits, and the angle from which it is viewed.

The images below are of the same blackberry, with the same camera and camera position, but with different lighting. The image on the left has a point source of light, and the image on then left shows the blackberry illuminated by diffuse lighting. The colors of corresponding parts of the two images are not the same.

Which blackberry looks the most succulent?

To define the color of an object, we need to specify the angles of illumination and of viewing. There are an infinite number of combinations, but a small collection of combinations have been standardized so that we can actually communicate about color values. The most common choices are 45/0 geometry (which is equivalent to 0/45) and diffuse geometry.

Am I done yet? No. Our perception of color depends (slightly) on whether it is a small object (projected onto just the inner circle of the retina, called the fovea) or a larger object (which extends to more of the retina). The relative concentrations of cones are different in the fovea than the rest of the retina, so our perception of color changes.

To define the color of an object, we need to specify whether the object is small (the 2 degree observer) or larger (the 10 degree observer). In case you are not confused enough yet, I discuss standard illuminants and observers in a blog post called How many D65s are there in a 2 degree observer?

In summary, the color of an object is a property of the object itsewlf, but also of the spectral composition of the incident light, the angles of incidence and viewing, and the size of the object. Based on that, once you have specified the L*a*b* value and all of these conditions (by saying, for example, 45/0 geometry, D50 illumination, 2 degree observer), you have defined the color sensation, and the color of the object has been defined.

So the second answer is that, for an L*a*b* value to have a precise meaning, you have to specify the instrument geometry, the illuminant, and the observer (2 or 10 degree).

Note that this does not mean the object won't have a different color under different conditions. Sorry for the double negative. Lemme try again. Objects in the mirror may appear closer than they are. Product is measured by weight and not volume some settling may have occurred during shipping. No warranties are express or implied. And, the color of your tie and sport coat may not match under the funky mood lighting when you get back to your apartment.

Practical answer

There is another important definition for anyone in the business of making stuff that has a specified color. Color is defined as that thing that the customer is willing to pay you for, provided you get it correct. It is whatever is defined in the contract. Without a contract detailed enough to have teeth, the correct color is whatever the customer likes.

The astute print buyer will recognize that his Wheaties package might be sitting on a shelf right next to another Wheaties package that was printed in a different press run or even at a different plant. The astute print buyer will recognize that an off-color package (just like an off-color joke) runs the risk of sitting on the shelf until expiration date, at which time it will get thrown out, much to the dismay of everyone who hates to see good Wheaties go bad.

This astute print buyer will also recognize that metamerism could be an issue if different sets of pigments are used to create the ink on the package. In that case, the astute print buyer might see fit to define the color in terms of spectral values, or in terms of color specifications under multiple illuminants.

So, all those previous answers are just academic if you live in the real world and want to get paid for your print job!

The standards folks, I might add, are pushing for a spectral definition of colors. Various tools are being put into place to allow the standardized communication of desired spectra.