Busting the Megapixel Myth

So the Average Joe just bought another digital camera. He saw the fourteen megapixels advertised for a compact digital, and immediately emptied his wallet. Had he known a little bit better, he could have bought something more worthy. Though if you are thinking that he could have saved some money too, that does not happen in the digital camera world. Good things come for a price, and his wallet would have been emptied regardless. However, there is one irrefutable fact. That there are worthy products available to suit wallets of all sizes.

The digital camera marketplace is a tough place to be at for the customer. The multitude of manufacturers and their countless products do not make for a customer centric market where the customer has a lot of choice. It only goes on to confuse a prospective customer so much that he more often than not ends up getting a product that does not serve the purpose to begin with. All this happens because of numbers. Numbers are a very big and very strong part of all advertising. The general perception is that if any product sports a bigger number than some other competing product, its gotta be good. And as a result, the advertisements focus primarily on numbers. And imagine the impact that a number that runs into the millions has on a customer and this is where the megapixels come into play.

Back in good old film days, we just had film frame sizes. There was large format film for the serious professionals and the nuts, there was medium format film for the smart professionals and the enthusiasts. And there was 35mm film for professionals whose job demanded extreme flexibility. And the same 35mm film was also for the rest of us. For years, nay decades the 35mm film ruled all family, amateur and photojournalist photography. Film was just film, an analog medium with no specific method to calculate the resolution in terms of megapixels.

Then came along the digital age, and as with all things digital, there were numbers attached to the size of the image that you could make with a camera. Starting off in the kilopixel domain, over time these reached the megapixel domain. And then began the megapixel wars that still continue to the day.

Before we delve deeper into megapixels, let us understand what a pixel is - a picture element. One pixel represents a colored (and in olden days a grayscale or even a monochrome) dot. And the entire image is made of a huge number of these pixels. Whether it is your computer monitor, or a digital camera photograph, or even a digital print - all are made of thousands or millions of these pixels. And if ya get together a million of these pixels together, it makes for a million pixels - or a megapixel. And if the total numbers of pixels that are contained in the output file from your digital camera is about ten million, the manufacturer will proudly call it a ten megapixel camera. Now these eight million pixels are often arranged in some accepted aspect ratio form factor - such as 3:2 (the classic 35mm film full frame) or the 4:3 or 5:4 ratios that some other people prefer. And thus those ten million pixels that are crammed onto the digital imaging sensor of the camera would be arranged into a 3650pixel by 2750pixel grid for a 4:3 ratio, or some grid with other vital stats for different aspect ratios.

Now there might be a six megapixel camera, an eight megapixel camera, a ten megapixel camera, a twelve megapixel camera, a fourteen megapixel camera and even a twenty-one megapixel camera. Now, the Average Joe who is doped heavily on the camera advertising will immediately pick the twenty-one megapixel one, see the price & have a near heart attack, then pick the fourteen megapixel compact and get going, laughing on all those who are lining up for the larger in size and much costlier camera that has just "twelve" megapixels. Little does the Average Joe know that Not all pixels are created equal. Heck he perhaps doesn't even know that the six megapixel camera that he did not even look at might net him much better pictures.

All this megapixel craze has significance perhaps only in the digital age. Back in the film days, the primary factor was what film were you using, and equally important was the quality of the glass. And more importantly, you just took the photographs, and then got them developed on a decent sized paper. You did not blow them up to insane sizes of pixel to pixel magnification on your 24 inch monitors. And even if you wanted to use those images on the computer monitors, would you actually put them at pixel to pixel zoom, or fit to the screen. And in fitting to the screen, there is not a single monitor available on the market that has more resolution than the cheapest camera available on the market.

The camera was practically not a big factor in image quality, unless somehow a bad camera messed up with some of the exposure parameters and killed your photograph, or exposed the film from some stray light that entered into the camera from somewhere that it shouldn't have. But in the digital age, they messed with all that. What with the image sensor being a part of the camera and that they created all sorts of smaller sensors to enable having smaller optics and as a result more and more compact cameras. What they effectively did was that the physical size of the pixel became smaller and smaller to allow for small sensors and large resolutions. And with that, while the continuously improving technology allowed for each increased resolution (i.e. smaller pixels) to not get completely messed up, the small sensor compacts can not at all match the picture quality pixel for pixel and thus of the photographs taken by the larger sensor DLSRs. Heck sometime what may even happen is that a lower resolution compact may have a better image quality than a higher resolution one because the megapixel count resulted in pixels so messed up that well, the entire image is messed up.

To understand that more clearly, we might have to go a bit deeper into how the digital camera image sensor works. Each one of those millions of pixels of the digital sensor is a photosensitive site, and as light falls on it, it generates a signal which is stored into the memory as the photograph. Of-course there are things like micro-lenses and color filters and Bayer filters are involved, but that is a discussion for another day. So if you cram a lot of megapixels on a small sensor, each pixel gets smaller and smaller, and thus it has lesser and lesser area for light photons to hit the pixel and as a result the response of the sensor to low light takes a solid hit, as does the per pixel clarity due to a variety of factors including diffraction.

Now suppose that you have two cameras, both of the same resolution, say ten megs. One is a compact with a super shrunk sensor, the other is a APS-C SLR. The ratio of the size of each pixel sites on those cameras is perhaps close to ten, or even more than that - means that atleast 10 times more light goes into making each pixel of even an entry level SLR than a compact. Couple that with the larger pixels that require less lens resolution per unit glass area, and it means that the flaws in glass are not so pronounced. What finally results out of the SLR sensor is a picture that has much more per pixel detail and sharpness, and hence the phrase "Not all Pixels are created equal".

So the next time you go out to empty your wallet at the cameras store at the mall, just think for a while what you actually, and how big prints would you actually be making, or for that matter, even the resolution of your computer monitor. Just don't go out and buy the highest megapixel pusher you can, take a look at what kinda pixels it spews.

The Connecting Rod

So, a few days ago back in India, while I was at the new Canon Experience at the Ambience Mall, Gurgaon, checking out the 5D, the salesman, recognizing me as an automobile fellow from my company uniform, asks me a few things about car engines. And thus, an unlikely connection was made between my two passions.

As a result, today I will be writing about cars and all.

My parents tell me that my love affair with automobiles goes way back, and that the first word I spoke was "car" contorted into something that can be blurted out by a toddler. As a result, gasoline was in my veins even before I knew that such a phrase actually existed. All my toys were cars, and after the ten or twenty customary hours of playing, all were disassembled to take a look into the mechanism that made it go, or made the vroooooom noise as it went and the like. I was a born engineer.

Thus, it was no wonder that when I was old enough to understand these, horsepower, torque, cubic capacity, four wheel drive, transmission ratios, synchromesh, differential gear, pistons, cylinders and connecting rods were the most used terms in my vocabulary. I started pouring the hours into reading whatever automobile magazines I could get my hands on, and as a result, got to know a lot about automobiles. Some of it I have already forgotten, and before I forget the rest, I guess I should put it down here.

The earliest automobiles (lets just restrict our scope to the internal combustion kind for the sake of logistics) were made around a hundred and twenty years ago, in Germany (where else - that place still is the mecca of automobiles - irrespective of what others might want you to believe - and anyone who knows his beemers and audis from the hondas and chevys will vouch for). Then on, it has been a pretty long journey of evolutions and revolutions in automotive technology, which, the way things are looking, will frankly never come to an end.

The earliest automobiles were often popular as horseless carriages, as they were actually those things retrofitted with some sort of engine driving the wheels, and also some rudimentary steering system, lest you drive head-on into the walls or someone walking by the side of the road - or even in the middle of it - as must have been the norm for those days, and apparently still is in my part of the world.

Today's cars are in principle not much different from what those earlier ones were, engine driving the wheels; steering to avoid the obstacles. Though a lot of other things have been added over the years: suspension, brakes, doors, roofs, windows, roll down glass windows, intricate transmissions with multiple gears and later automatic transmissions, seats, seat belts, the instrument panel with (now-a-days) countless tell-tale displays, luxury and convenience things like the air-conditioner systems, radio tuners, full fledged multimedia and navigation systems, safety features like ABS and airbags, and in more recent years lots of electronic jugglery like stability programs, traction control systems and what not.

The earliest vehicles were rear wheel drive, and for a long time, it was the tradition to have the engine up-front under the hood and drive the rear wheels. And if I am to believe the words of the editor of my favourite automobile mag (which I do), it still is the ideal way because "After three months with the 320d, I now know why the power needs to go to the back and the front should be left to do the steering and not battle with the power transmission." This traditional longitudinal front-engined rear wheel drive way of building cars has now been mostly cast aside, sometimes resulting in legends like the rear engined 911s from Stuttgart, mid-engined beasts from Maranello, but sadly for the most part leads to the sea of transverse front-engined front wheel drive cars that we see today swarming all around us like buzzing bees threatening to swallow the few remaining bastions of sanity.

Prejudices aside, the transverse front engined way of building cars is economical and also weighs less because all of the drive train is contained under the front hood. That is perhaps why it is so famous today. The conventional layout is still religiously stuck to by a few and for good reason. Their reputation & identity lies with it. Though with the rising concerns about the environment and the governments taking sterner than ever looks at the miles per gallon figures, it might be a losing battle for these few.

Coming back to the technical stuff, cars have been traditionally propelled by petrol engines, that magical liquid that you get from black gold - crude oil. Referred to as gasoline by the people living in the land of a thousand dreams, this fuel now has some serious competition from the likes of the diesel engines, which for decades were foul smelling, smoke spewing, noisy, overweight chunks of metal, fit only for marine, stationary and truck applications. These days however, so much has changed that unless you pop open the hood of a car, you will not be able to recognise one from the other by performance and sound. So much so that one of the pinnacles of motorsport is so thoroughly dominated by "oil-burners" that the organising agency is trying to amend the rules in the favour of the spark-plugged variety.

Coming to the next thing after the engine that sends all those horses and Newton-meters to the wheels is the transmission - also referred to crudely as the gearbox. From the preselector gear transmissions of yore, through the sliding mesh and synchromesh manual transmission on the manual side to the "hydramatic" and "tiptronic" to the latest fancy dual clutched variety on the automatic side, the transmission has also seen perhaps as much advancement in technology as the the engine has. From simple device designed to provide varying levels of torque as per the vehicle speed and load requirement from the engine, to a highly tuned and integral part of the vehicle upon which huge aspects of performance and luxury depend, the transmission has come a long way.

They used to have a drive shaft earlier in almost all vehicles, but now-a-days the differential built into the transmission case eliminates the need for that. The differential gear however is here to stay, lest the vehicles spin their wheels bald on turns or worse, under steer so severely that the roads would have been planned in a totally different way.

From sticks that you could lower to the ground to cause some resistance to motion and leather bands that could be pulled to tighten around the wooden wheels of wagons, brakes have come a long way today, what with the cross drilled ceramic discs and ten piston calipers. If you go ahead and calculate the amount of stopping power today's brake systems have, you would wish for some magical device of the size similar to the brakes that could generate even half in absolute number the braking power.

Anyway, I could perhaps go on and on about the things that make up a car. Heck I haven't even touched the system that I actually deal with in real life in the car company that I work for, but it would perhaps be fitting to leave that aside for some other day.

Jargon for the photographer

Well, as the psycho sits in-front of his computer monitor, thinking about the many many things that can be put down in today's post, photography once again draws his attention.

So here's today's post, filled to the brim with all sorts of terms about photography.

1. Shutter-Speed:
Well, shutter speed is not a technically correct term, as every speed is usually measured in "per unit time" terms, but, shutter-speed is measured in "time" terms.

It is the duration for which the shutter of the camera remains open to allow the light to fall on the film/sensor to create an exposure.

Some of the typical shutter speeds are 1 sec, 1/2 sec, 1/4 sec, 1/8 sec, 1/15 sec, 1/30 sec, 1/60 sec, 1/125 sec, 1/250 sec, 1/500 and 1/1000 sec. On modern cameras, this scale is extended on either side for more control on the photographic technique.

The shutter speeds are also sometimes mentioned as the reciprocals of the time in seconds for which the shutter is open. This way, a bigger number does indicate a faster shutter speed, e.g., 1000 (1/1000 of a second) is a much faster shutter speed than 60 (1/60 sec). (This shutter speed is also related to how some lenses are called "fast" - but we'll get to that when discussing Aperture and F-Number).

There are various photographic technique terms related with shutter speed, such as stopping motion, motion blur (& panning), long exposures, blurring etc. Another related topic is Image Stabilization, especially for hand held exposures in low light conditions where the shutter speeds are slow.

Another Jargon term related to shutter speed is X-Sync, but we'll discuss it later.

2. Focal Length, Field of View & Crop Factor:
In a photography system, the focal length is usually referred for the focal length of the "Lens" that isn't just a piece of glass but is actually an optical instrument made of multiple glass pieces.

The Focal Length (in photography) is the distance from the rear nodal point (virtual point at which all light rays from outside seem to converge before emanating towards the sensor/film) to the image plane, where the film/sensor itself is placed, when a subject at infinity is in sharp focus.

The term focal length does not have to do much with the focusing of the image, but actually is closely related to the field of view. The field of view is the angle measured horizontally, vertically or diagonally that is seen by the film/sensor of the outside world being photographed.

A shorter focal length lens has a FOV, and is thus called a wide lens. This is because the image plane being very close to the rear nodal point, the film/sensor subtends a very large angle at the nodal point and thus can also see this same large angle of the outside world.

Conversely, a longer focal length lens has a very narrow FOV. Such lenses are called tele lenses or long lenses.

If you hear someone speaking the words "normal lens", it is a lens that has a 35 mm equivalent focal length of 50 mm. It is called such because this focal length produces images of same magnification and perspective as the human eye.

The "35 mm equivalent focal length" thingy might be slightly confusing - as the FOV depends both on the sensor size and the focal length of the lens, and because the 35 mm film system has been really popular for a long long time, most of the manufacturers of digital cameras (whose sensors are usually much smaller than the 35 mm film frame size of 36 mm x 24 mm) give the equivalent focal length so that photographers can easily estimate the approximate FOV. A small sensor needs a smaller focal length to give the same FOV. Thus, if a sensor is 18 mm x 12 mm in size, a lens of focal length 25mm will give the same FOV as a 50 mm lens on a 35 mm system film frame. This particular camera manufacturer will state that its 25 mm lens has a 35 mm equivalent focal length of 50 mm. A multiplication factor of 2 is used here, and this is also called the "crop factor" of this particular camera system. (My Panasonic DMC-FZ50 camera uses quite a small sensor, and thus its zoom lens of 7.4 mm to 88.8 mm focal length has a 35 mm equivalent focal length of 35 mm to 420 mm, the crop factor being about 4.729).

For larger formats (film size larger than a 36 mm x 24 mm frame), the crop factor/focal length multiplication factor is a number smaller than 1. A normal lens for such systems has a focal length larger than 50 mm.

3. Aperture & F-Number:
The aperture is the size of the opening that determines the amount of light going through the lens to fall onto the film/sensor. One more thing to be kept in mind is that the amount of light does not only depend on the size of opening, but also the Focal Length of the lens being used. For example, a 25 mm aperture on a 10 mm focal length lens will admit the same amount of light as a 50mm aperture on a 200 mm focal length lens. Thus, the more popular term used in the realm of photography is relative aperture - and this is quantified by the F-Number, which is the ratio of the focal length to the aperture diameter. A 50 mm focal length lens with a maximum relative aperture of 1.4 can be designated as 50 f/1.4.

One thing to remember very clearly here is that the smaller the F-Number, the larger the aperture.

Successive sizes of relative apertures are called aperture stops - or F-stops. Now, as we have already seen that the shutter speeds are in multiples of two. thus to maintain a parity in the system, the total light falling onto the system at two successive aperture stops must have a ratio of two - and thus the F-Number must have a ratio of the square root of 2. This is simplified to 1.4 in photography systems, and thus you can see F-Number stops of 1.4, 2, 2.8, 4, 5.6, 8 and so on. Each successive F-Number stop halves or doubles the amount of light it allows to pass, and thus to maintain the same exposure, the shutter speed is also to be adjusted by one stop.

Now, a F-Number of 1.4 allows a LOT of light into the camera, and thus, in bright light conditions, one can use a very fast shutter speed to get a good exposure. Thus, a f/1.4 lens is called a fast lens. A lens with smaller F-Number is always a faster lens than one with a larger F-Number.

There is another property of lenses called "depth of field", which is directly related with aperture, but it being a slightly advanced topic, we'll discuss it some other day.

4. Prime Lens & Zoom Lens
A lens with a fixed focal length (fixed FOV) is called a prime lens in camera terminology. For long, the only lenses that were available on the market for cameras were prime lenses, and even today, the best pieces of glass are primes.

A lens that can vary its focal length is called a Zoom Lens. These are becoming more and more popular these days, and with advances in technology are now beginning to tread on encroach on prime territory.

While not better in versatility than zoom lenses, they are clearly superior in terms of optical quality - exceptional sharpness and non existent distortions; they are often much faster than zoom lenses; they also are available for focal lengths the zooms dare not touch. With a faster prime, you can stop motion, or get good snaps in low light. Other than that, because of the sharpness and distortion advantages, the resultant image quality is also better.

Zoom lenses on the other hand are so much more versatile. You need not move to frame your shot perfectly just twist the zoom ring, and in some cases, perfect framing absolutely cannot be achieved by moving if there are some obstacles or unreachable places. Though traditionally slower and optically inferior to Primes, Zoom lenses are popular just because of the versatility they offer. Lens makers are proud to office the best zoom ratio - the ratio of the wide end to the tele end of focal lengths - these days the number often being greater than 10 in the do-it-all.

One specific trait of zoom lenses is that their maximum relative aperture (F-Number) varies with the focal length. A typical Zoom Lens might be designated 18 - 50 mm f/3.5-5.6. This means that the F-Number of the lens is 3.5 at its 18 mm wide end, but goes to 5.6 at its 55 mm tele end, thus being over a stop slower.

With advances in technology, the zoom lenses have over the years advanced in optical quality, and the best ones are now reasonably fast too (f/2.8 throughout the focal length range - though the zoom ratio is usually limited to 3 on such lenses) but you still cannot get a f/1.4 or a f/1.2 zoom, and perhaps never will.

There is a lot more to write about photography and photographic equipment, but for the day this should suffice.

Tools for Drawing with Light

Ah yes, the tools of drawing with light, or in simpler terms, cameras.

As some of you might know, cameras and photography are my newfound passions, and as a result, in the recent few months, I have done a good amount of web-scanning on cameras. While that reading has been primarily on Digital SLR cameras and their lenses, in this first post I should perhaps refrain from going into that specialized topic. SLR's, Digital SLR's and Lenses will be the subject of future posts on this blog, so will be photography. But as of now, lets deal with cameras.

Well, for some, a camera is used to turn moments into permanent memories (well, as permanent as this universe allows), and for some, it is the brush to paint on a chemical canvas. And technically, a camera is a device to capture and reproduce some visible part of the universe, whatever it may be.

These days, there are primarily two types of cameras available. The ones that use chemical based film to capture the images, and these have been around for more than a century and a half now, and the ones that use a digital sensor. The second type have been gaining in popularity over the last decade, and their numbers are snowballing now.

If I start to discuss the chemical film and digital sensors now, it will be ages before I will be able to get back to the topic that I am actually writing on, so I will for now get back to what the rest of the camera needs to do, and will take up these two things sometime else.

While over the ages, there have been countless new features and technologies added to cameras, the basic principle, as with perhaps all things has remained the same. A closed box with an opening or a lens at one end to allow light to enter and create a image. (And use that film or sensor to capture this image).

The type of camera that has only a small opening at one end and no lens is referred to as a pin-hole camera. The light simply passes through the small hole and forms an inverted image on the back surface of the (almost always) cubical box that is the pin-hole camera.

For the camera that have them, the lenses take upon the job of creating an inverted image of the scene in-front inside the camera. One important thing to note here is that each lens has an focal length and this focal length is the distance behind the lens where the image (of objects at infinity) is formed inside the camera. The film or the sensor needs to be placed here to get a sharp and defined image. For objects that are closer than infinity, the distance between the lens and the image plane (the place where the image forms and the film/sensor is placed) needs to be altered. And this process is called "focusing". On modern cameras with modern lenses, that actually are complex devices themselves with multiple pieces of glass that can move to focus, and on zoom lenses, even vary the focal length so that the field of view whose image is formed and captured differs, this process no longer requires the actual lens to be moved - just one or more glass piece of it. And the focusing now on most cameras is done automatically - using distance sensors and servo-motors and what not. Focusing speeds faster than that of the human eye have been achieved in professional lenses, and it can only go faster and more accurate than ever before.

Well, lets get back from that focusing detour and continue with the camera. If the light always fell on the film/sensor, it would actually create nothing but a totally white image. Thus, the amount of light that falls on the film/sensor needs to be controlled, so that a photograph that looks usable and good is formed. To do this, there are quite a few mechanisms available on the camera and also a lot of assisting aids.

The first and foremost of these things is the shutter. As the name suggests it is an object used to "shut" out the light. It allows the light from outside to enter the camera for a fixed duration that is usually a fraction of a second.

Another way of controlling the amount of light is the size of the opening at the front of the camera. It is called the aperture and is usually defined by the aperture number of the f-number, which is the ratio of the focal length to the aperture diameter. Some simple geometrical maths says that for a fixed f-number, any focal length would require the same amount of shutter open time for the same exposure, provided that the ambient light intensity remains the same. And this is why the f-number is a very important parameter. The catch here is that the smaller the aperture number is, the more is the light that passes through (it is inverse square root ratio) and smaller is the shutter time that can be used(faster movement of shutter), thus giving the name to large aperture(small aperture number) lenses of "fast lenses".

There is another way of allowing the shutter speed to be slower or faster, but that is to do with film types and sensor sensitivities so we'll deal with it some other day.

To guess the combination of aperture size and shutter speed to get a good exposure is not something everyone can do, and this is how we reach at what even the "pros" - who often say that the camera is the least important thing required for taking a photograph - say is a most crucial thing - the "meter". Short for light meter, this (now) tiny device measures the light intensity and suggests the shutter speed for a set aperture - or vice-versa. Modern meters are TTL - through the lens - judging the amount of light coming from the actual scene that you are going to photograph and thus more accurate, and are now usually linked electronically to the camera's automated shutter speed and aperture setting systems to give you a point and shoot system - no need of fiddling with the settings to get a good shot. There are a lot many new jargon-words attached with the metering systems of these days, that if used properly provide good tools to utilize the camera that bit more effectively.

Another very important thing that I almost missed out telling about is the viewfinder. What good is a camera if you cannot estimate what it is going to photograph? The viewfinder is that which lets you see the thing that the camera is supposed to be seeing - and in case of TTL viewfinders - what it is actually seeing, to help frame your shot. The non-TTL viewfinders have a parallax error that gets pronounced with closer objects being photographed, and thus are not the ideal solution. The TTL viewfinders are harder (read costlier) to achieve, and while traditionally are found only on costlier SLRs (Single Lens Reflex) cameras (we'll discuss these in good detail some other day, don't worry), these days electronic TTL viewfinders and screens are very popular on the digital cameras. It is an optical TTL viewfinder still that is elusive, because it is the best.

There are other things like the film advance system (for the film-roll cameras) - both manual and automatic, some sort of displays to show what the camera is going to do the next time you press the shutter, some buttons for direct functions etc. etc. On modern digital cameras, there are increasingly larger color LCD display screens that show the images, menus for settings, previews, and also lots of buttons to navigate the menus and set the settings.

Well I guess for today this is a good thing to read about cameras, and I guess I will be writing a LOT more about cameras, types of cameras, lenses, digital camera technology, photographic films, photography and camera jargon, camera and film formats, silver halide, megapixels, depth of field, bokeh, primes, zooms, superzooms, point-and-shoots, full-frames, rangefinders, 35mm...

The list goes on, and so do writing opportunities, and someday I hope to have written enough about cameras and stuff that I have no more to say.

Let Us Begin "storing"

Because this is the very first post of this new blog about things that I have known, I will stick to the topic that has been deeply rooted inside of me for so long now that I can't even remember how I ever got interested in it.

I'll stick to computers. And because I know a good amount about them, I'll further refine the search parameters to hard disk drives.

A fair bit of people will know that the first ever commercially available hard disk drive was made by IBM in 1956, and was called the IBM 350. this 60 inch long, 68 inch high and 29 inch deep monster had a capacity of about 4.4 megabytes. Compare that to a typical 3.5 inch format drive (4 in by 1 in by 5.75 in) of today that can store about 250000 times more data, and you will know how far we have come in the last 50 years or so.

For the personal computer, the first ever Hard Disk was made by Seagate, the company which is today the leading manufacturer and supplier of PC hard disk drives in the world. Introduced in 1980, it was called the ST-506, was 5 megabytes in storage size and fit into the 5.25 inch form factor popular at that time for floppy disks (We'll discuss floppy disks some other day, despite the fact that they have now entered oblivion with many other types of more flexible and reliable storage technologies emerging).

The HDD is a magnetic device, and despite the reduction in size and the huge increase in storage capacity, the underlying technology principle has remained same. It has however seen countless technical revolutions, and most these days quote the terms like magnetoresistance, Giant magnetoresistance (GMR), perpendicular recording and so on. We'll leave these for another day and for now concentrate on the basic technology.

Each HDD has a spinning spindle with a number of platters (disks made of non-magnetic material but coated with ferromagnetic substance - thus making the device primarily magnetic in operation), onto which directionally magnetized zones are created by the write heads, and the data thus stored in forms of binary bits, zeroes and ones depending on the direction of magnetization, is read by the "Read" heads by detecting the magnetization direction. The platters spin at very high speeds, usually higher than your car engine speed. And there are multiple platters, each with two usable surfaces and two sets of read-write heads to use 'em.

The growth in the storage capacities of disks hasn't been by adding more or larger platters as we can see by comparing the sizes given above. It has been made possible by shrinking each magnetized zone smaller and smaller into the electron microscope territory. Those big buzzwords you read about the technologies are all the ways to do precisely this and still get away with it.

And the spindle spinning speeds, they have gone from a respectable 1200 rpm on the original IBM 250, to 15000 rpm on the fastest available disks today. That's statistic alone is enough to get one's head spinning.

Approaching the end of today's lesson, it'd perhaps be best if I list the stats of the newest HDD that I have in my computer (a January 2007 piece), so that a few years hence I may laugh madly at it.

Hitachi Deskstar 7k320. 7200 RPM, 320 GB

We'll get back to HDD's some other day, when i'll perhaps touch upon somethings left aside today, and also post a glossary of related technical jargon.

PS. Next stop on this station - Cameras.