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.