A Snapshot of Photography - 1

Just what is the difference between your tiny 7 Megapixel sureshot camera, a large sports camera, a huge portrait camera, and all the plethora of high-resolution movie cameras available today, and all in-between?

The answer is: Not much.

There are always a few basic attributes they all have - it is just a matter of degree.

However, there are a few terms they all use which have the same function.

1. Aperture

2. Shutter speed

3. Focal length

4. Film speed

5. Negative size

That's it! Here's the explanation of each:

Aperture is the hole that allows light onto the film. The bigger the hole, the more light is let in.

Shutter speed is the time during which you let the light in for. You can see that if you have a small aperture, you need a slow shutter speed, and for a large aperture, you need a fast shutter speed, to let the same amount of light onto the film.

Film speed is how quickly the film reacts to light. In the examples above, the conditions in both cases will let roughly the same amount of light onto the film. BUT, if you use a 'fast' film, both images will be brighter.

Focal length is simply how far into the distance you can see, exactly like a telescope. However, because you are looking at a smaller area, there is less light coming in than normal, and so you must use a slow shutter speed.

Negative size governs the quality of the image developed from the negative.

A few examples may suffice. In sports, you often see close-ups of the action as a basketball shot is made. The photgrapher uses a telephoto lens for this, typically six times more powerful than normal. Therefore he must let six times more light in. he can't use a slow shutter speed as this is action and the image will be blurred. He uses a combination of a big aperture (this is why you see these lenses looking like megaphones) and fast films. The lenses use much glass, which makes them very expensive (about $3000 each), and he has to decide what film to use.

In a panorama shot, you have to go the opposite way, using an 'anti-telephoto' lens, commonly known as a wide-angle lens, or sometimes a 'fish-eye' lens. You would think that seeing more gives you more light, but it does not! So again , you have to use a long shutter speed (not really a problem as nothing is moving). You solve this by putting the camera on a tripod to steady it.

Then there are the zoom lenses, used in the movies. This allows the image to be 'zoomed' in on and makes the action better looking.

A normal camera you buy in the stores tries to mimic the action of the eye, as in aperture and exactly how much you see. This is the angle of vision, and normally, when focussed ahead, the eye can acually 'see' out of the 'corner' of the eye, up to maybe 120 degrees. The camera lens is quite at about 60 degrees, and most everyday lenses use this. The ratio of focal length to film size has to be between 1.3 and 1.42 for this to work properly (Why? Trial and error 100 years ago!), so for a 35mm camera, you get a 50mm lens. If you call this 'normal' aperture '1', then a 300mm telephoto, (six times magnification) will have an 'aperture' of about 1/6.

Well, that is the simple bit over with. Next time will be about 'pushing film', 'exposure compensation', 'depth of field', 'lens flares' and that bane of the Dark, the Dreaded 'Reciprocity Failure'.

Confusion from the Sun

For years, warnings have been given about exposure to the sun's rays because of the risk of skin cancer.

Now, there's this...

http://news.bbc.co.uk/1/hi/health/4585751.stm

It is now better for you go even go unprotected in the sun because of the increased vitamin D.

So, we now have a choice - normal lives, or, melanomas with increased vitamin D.

The scientific press sometimes get it all horribly wrong.

I'm wide awake at 4am....

...without a friend in sight...
...I'm hangin' on a hook, but I'm alright...

One night in May. Istanbul. European Champions League Final.

Liverpool (my adopted City)

versus

AC Milan

A night no-one in Liverpool will ever forget. May 25th, 2005.

(The original video was taken away from youtube, but I replaced it with this one)

Since I lived in Korea for 5 years, I was lucky enough to experience the month-long World Cup of soccer there in 2002. Those memories will stay with me forever, especially as Korea came 4th.

However, the video below surpasses it all. Liverpool had won this competition 4 times previously, and interest in the UK was high. We set the alarm for 4 am (hence the song - name it anyone?) and waited for the kick-off at 5 am.

Those of you not in the know, "soccer" is called "football" in England. It was called "soccer" because the original name of the sport was "AsSOCiation Football".

Normally, in a game of soccer, you can expect only one or two goals. 3-4 is quite rare. The game below has six.

AC Milan are one of the best Italian teams, and in the first half, they took Liverpool apart like they weren't there. Liverpool 0 AC Milan 3.

Then came the second half. We only got Korean commentary and afterwards, I downloaded the full match with English commentary.

A few minutes after the second half began, Steven Gerrard, Liverpool's captain and mentor, scored a goal to make it 1-3.

The english commentator made a telling comment as the ball went into the net. He said "Ello! Ello! Here we go", a reference to the fact that in all their history, Liverpool Soccer Team "never say die", a point well-made owing to the Team's determination to win despite the odds.

So the commentator was remembering what had happened in previous years when Liverpool had been down, but at 0-3, Was it possible?

The answer came minutes later and the score became 2-3. The Commentator then said "Miracles CAN happen!".

The rest I leave to the video.

At this level, if matches are tied at the end, they play an extra 15 minutes, then, if still level, the two teams are given 5 "free kicks" each, with only the man in goal to beat. These are called penalties.

The team scoring the most goals wins.

Suffice it to say, at 7.30 am we were screaming and jumping around!

One Night. Two Teams. One Trophy. 22 players and six goals. For soccer fans, it was a treat

Brucie vs Aki

Iron Maiden is one of the better bands , or, at least, they were. The lead singer used to be Paul Di'Anno but he was replaced by Bruce Dickinson, probably by Martin Birch, the mentor behind it all.

Bruce Dickinson was the master of at least two crafts - His music and Fencing (Not that type)

Bruce was once selected for the Olympics for his prowess with the epee (unlike Boris Onishenko).

He turned the offer down in favor of what he really wanted to do - his music.

My chosen subject was physics and it will stay that way.

Bruce Dickinson was never called a fraud.

I don't know the guy, but the guitarist Dave Murray has my pulses racing!

Even so, I really wanted to do physics, and I did well!

Can anyone get the 3 allusions here?

The Time Travel Paradox

A lot of people think that time travel to the past is just a matter of time.

An example of the problems therein is illustrated by the following paradox:

1. You build a time machine.

2. You travel back in time.

3. You meet your own grandfather when he is 20 years old.

4. He is so shocked he dies of a heart attack when you tell him who you are.

5. He never meets your grandmother, they never marry and never beget your mother.

6. You are never born.

7. So because you don't exist, you never build the time machine.

8. Without the time machine, your grandfather cannot die, therefore you are born.

9. So you build the time machine.

10 (See step 2)

Many scientists think that time travel into the past is impossible because of this reasoning.

Movie makers have made use of this idea in subtle ways. Star Trek IV; The Voyage Home uses transparent aluminum. Scottie gives the scientist of 1984 the formula for transparent aluminum, which is of course an invention from the future.

They then use it in the movie, giving credit that it was invented in 1984. So the invention originated in 1984. The question is: Where did the knowledge come from?

Another better example was in the Terminator movies. In T1, the Terminator was sent back through time to kill the hero's mother, because the machines were losing the battle in the future, the hero leading the humans seemingly to victory.

In T3, the third Terminator is again sent back to kill the hero, and to get to him, infects the machines with a virus. The virus causes the 3rd world war, and subsequently the new war against the machines, which the machines start to lose, triggering an action to send a machine (T1) back into the past to kill the Hero before he becomes powerful enough to lead the humans seemingly to victory.....

The loop is quite clear, although James Cameron wraps it up within 3 movies and a gamut of special effects.

This post is closely related to http://phdnotdph.blogspot.com/2005/07/is-time-travel-possible-honest-answer.html
But the point of view is diametrically opposed.


As Douglas Addams once said, the main problem with time travel is not the above, but of "tense". How on earth can you describe something which would have been done if you had done something else in the past future of the future past?

If you look carefully at the two examples, you will see the proof.

The Truel

PARTLY SUBJECTIVE POST!!

Please read the blurb before you click the video!






Westerns come and go, but this climax to "The Good, the Bad, and the Ugly" has to rank amongst the best. Apologies for this version, but this movie DEMANDS widescreen, especially here.

The "Good" (Blondie played by Clint Eastwood), the "Bad" (Tuco played by Eli Wallach) and the "Ugly" (Angel eyes, or Colonel Mortimer played by Lee Van Cleef) fight it out for $200,000 .

Things to notice.......Mortimer is the one with the tip of his middle finger missing, Blondie is the one with the perfect fingernails, and Tuco is the one wearing his gun around his neck on a string.

The director is Sergio Leone, and the music is by Ennio Morricone, in this the final instalment of the "Dollars" trilogy.

The use of music is impeccable as is the single crow sound at the end of the first stanza.

Leone wanted to convey how it looked from each character's viewpoint, as early on, the camera sits behind each of them.

They eyes are the key. Blondie only looks ahead to Tuco and Mortimer to his right, Tuco looks ahead to Blondie and to his left to Mortimer. Mortimer has to look both left and right.

The major key is Blondie's eyeline. Notice how he focuses more on Tuco toward the end , as if he is more afraid of him than Mortimer (yet he knows Tuco's gun is empty)

This is Mortimer's undoing, as he thinks Blondie is being distracted, and reaches first.....

Enjoy. The DVD of this is much clearer but in either version the 3 hours is worth the wait.

As well as science I also do movies as a hobby! (along with photography, travel, cooking, puzzles and music!)

Leone went on to make "Once Upon a Time in America", the Western that was given Carte Blanche by Hollywood, and so important was the music to him (again by Morricone) that he had the actors in it act whilst the music was being played to them on loudspeakers on the set. That movie is notable for it's extended Intro credits, about 10 minutes long, but that is another story.....

At Wits End.....

SUBJECTIVE POST!!!

....a little light relief.

When a bright and breezy youngster, I would sometimes let my sense of humor get the better of me.

For example, this true story was laughed about for years afterwards.

One of my hobbies is doing this puzzle, the Rubik's Cube.

I solved it myself when I was 13 in 1995. I had no instructions, I chose to actually "solve" it. I first got it about 6 months later, having no idea how. After another 2 months, I had it again, with a slight insight as to how. It soon became apparent that the corners were the real problem. It took me a whole 4 months just to work out how to do just the 8 corners. I used a 7-move operation called a "swashbuckle", which moved 2 of the corners around an axis, leaving everything else the same. However, I needed 4 of these to complete the 8 corners (28 moves). Furthermore, I needed 3 right-handed swashbuckles followed by a left-handed swashbuckle.

The third time I got the puzzle correct I knew exactly how I did it. After that, it was a matter of refinement and my quickest time was about 2.5 minutes.

Then I found out I could do it without looking at the actual moves, just the positions.

Finally, the showbiz touch came - I was able to make all the moves behind my back, only having a look at maybe 10 positions in all. Time to do this, about 7 minutes.

So I usually say " can do the Rubik's Cube behind my back". Now, I fool everyone by just saying "can do the Rubik's Cube backwards".

But I digress. I was at a party organised by our local Church Group in London. It happened to be a Fancy Dress affair, and I decided to enter.

But being me, I wasn't going to be a Morticia or Elvira ( I was only 15 anyway!), but something a little more original.

The youth club had a pool table, and I took with me only a bush hat. At the time I was really interested in science. The hat had a zipper pocket on it, and I stuffed some tissue into it to make it look like I had a huge lump on my head. On the pocket I wrote in big black letters, the single word "POP!"

I then took a pool cue and wrote a girls name on it. Her name was the same as a valuable red gemstone. I wore the hat, picked up the cue and lined up with everyone else.

There was Alice in Wonderland, the Tin Man, the Snowman, Mickey Mouse, Snow White, and Kylie Minogue. They were all obvious to guess, but who was I?

I was asked.

I told them.

" A Fizzy Cyst with Ruby's Cue".

Back to Basics: Just what is an equation anyway?

First thing I learned about math when a kid was that you can juggle numbers even though you do not know what they are.

You do it with equations. But what are they? The clue is in the name. Something is equal to something else.

example: 2 = 2

or 5 = 4 + 1

These are equations (In fact they are called identities)

Here's how you juggle...... start with 5 = 4 + 1, and add 1 to either side of the "=", and

5 + 1 = 4 + 1 + 1 is still true

Start with 6 = 3 x 2

and adding 1 you get

6 + 1 = (3 x 2 ) + 1.......(1)

You need the brackets otherwise you get

6 + 1 = 3 x 2 + 1 ......(2)

which may not be true ( what is 2 + 1 the multiplied by 3?)

You have to be careful. Best way is to think of the equation as a seesaw with the "=" in the middle, and the seesaw must always balance.


In (1) above you are adding 1 to each side, but in (2) you are only adding to the 2.

You can replace the numbers with symbols, use the same rules, and all still will balance, if you practice long enough.

Example...

Is this true?

2(x + 1) = 2x + 2.......(3)

It's easy to see if you multiply the left hand side out 2(x + 1) equal 2 x + 2! Easy! But what was x? Well, we didn't find it out, but we proved it was true, so ANY value as x would do, be it 1, 50 million, or 1729.

However, is THIS true?

2x = x + 4 .......(4)

Let's find out. Subtract x from each side

2x - x = x + 4 - x

which becomes...

x = 4

So this is true if AND ONLY IF x is 4

This is the difference. (3) is an identity (true for all x) and (4) is an equation (only certain values of x will do)

Math guys (and us) use identities to simplify our equations.

Homework... What is the value of x here?

3x - 1 = 6 x -2

Answers on a comment please!

A Resonant Discord

A lot of Americans know this footage very well. It's the collapse of the bridge at Tacoma Narrows, on Nov 7th, 1940.

What is little realised however, is that the phenomenon is well known to scientists.

It is called "Resonance" and is best described by saying that something is vibrating in a way it has always wanted to.

One of the best examples is on a bus, standing at traffic lights. The engine idles, and suddenly parts of the tubular structure inside go mad with vibration. Not all, only some. This is also resonance, the engine is vibrating at exactly the same rate that these parts want to anyway, so they go along with it. A bit like when you hear a catchy tune, you cannot help but tap your feet.

Everything has this property, and it is called "natural frequency".

The gales shown in the video above came along and rattled the bridge at just the rate it wanted to. In the end it was too much strain.

Here we come to the "A-Ha!" insight - take an ordinary milk bottle and blow into it. nothing usually happens, but tilt it and blow across the top. If you blow correctly and have the right angle, a pleasing , low, note is heard. This again is resonance. The air in the bottle is rattling at just the rate it wants to anyway because you are making it.

In the video, the Narrows are the bottle, the gale is your blowing, and the bridge, the air inside the bottle. Given the right conditions, the bridge sings a note! Only this note is so powerful it shatters the bridge.

This is an example of engineers not doing their physics homework.

See how many more examples you can find!

The Road Goes Ever On

A bit more math. Has anyone ever heard of Clebsch-Gordan and Racah Coefficients? No-one outside quantum mechanics, I expect, as only quantum mechanics uses them. We certainly need them and they are very complex indeed.

There are no numbers, just symbols. Forgive me if I cut and paste from the 'net as there simply is not any other way to show them here.

These are the Clebsch-Gordan Coefficients.



These are the Racah Coefficients.

Before I lose the reader completely, let me tell you a story.

It begins with Newton's Laws, the first one to be precise. Harking back to my post on these laws, it states that "an object moving will keep on moving, or if at rest, will stay put unless moved"

We say a moving object has "momentum" and a stopped one, "inertia". The above math is all about momentum, and we measure momentum (p) most easily by saying it is " mass (m) x velocity (v) " . However the above is not about "linear" momentum, which is "mv", but "angular" momentum, which is defined similarly, thus: Angular momentum L is (angular inertia) I x (angular velocity) w

These are roughly the same as their linear counterparts. I is the equivalent of mass, and w is the equivalent of velocity.

I is a bit difficult to understand, it is the "moment of Inertia" of a body, and different bodies have different I's, some of them even have more than one. Here is a table to illustrate:


These objects have 2 distinct moments of inertia depending on which way you spin it.

Notice earlier how the words "velocity" and "angular velocity" were used. "Speed" and "spin" were not used because velocity is what we call a "vector" - it depends which way it points. Example, my car's speed is 30 kph no matter which way I turn it. However, if I drive north at 30 kph for an hour, then turn round and go south at the same speed for an hour, I will end up where I started. The speed was the same, but I used two different but equal (and opposing) vectors that cancelled each other out.

This, in essence is what these coefficients are all about. Example, if I take a vector east and travel for 12 km, and then south for 5 km, I won't finish 17 km away from the start, but 13km. (how do I know this? Try Pythagoras' Theorem). So when you add vectors, you have to notice which way they point and do the geometry.

Quantum mechanics does this, but at this level, momentum and angular momentum are quantised (only come in little bits at once), so special math are needed to do the geometry. These are the Clebsch-Gordan and Racah Coefficients.

Well, that is the background, angular momentum and vectors. Now for the rub.

The key to the idea is this. It is best to go back to my East-South car journey. How many ways are there to get from the start to the finish? I already gave one, but there are others, 5 km west, then 17 km east, and 12 km south is another. But the best way is the original one, 12 then 5 km.

Quantum mechanics, though, has to deal with all possibilities of the combinations of these vectors, and though none are equally likely, we need math to tell us how likely the car would would go West5, East17 (Brian, sit down!), South 12.

The Clebsch-Gordans tell us how many ways we can do it with two vectors (E - S , hence the j1 and j2), and the Racahs tell us how to do it with three (W - E - S, hence the j1, j2 and j3). The twiddly bits j12 and j23 just ask us which is first.

The "| >" , "< |" and "< | >" bits are actually indefinite integrals (yes, calculus) and the big mouths (the big bold symbols after the equals), are simply the adding up of all the bits we know about that follow after it.

That is the interpretation of the above. "Coefficients" is the name of a number we put in front of something we don't know to tell us how much to multiply it by.

The best way to put it is this: How do we get from A to B quantum mechanically? Answer: Add up all the probabilities of all the different ways we can do it to get "1" ( it is certain we will arrive at B). In this case, we have several quantum mechanical angular momenta, and we want to add them up. These formulae tell us how to do it and get an answer as to how probable it is that we will end up with a certain answer.

We don't know what it will be, but essentially we plug in the numbers for the J's and m's and M and we will get a big J. The j's are the individual angular momenta, and m's are the spin angular momenta, and the J and M are the probability of getting a certain total at the end from all the others.

Plug in the numbers, turn the handle, and out come the answers.

This is once more just an introduction, and the Road Goes Ever On.