Pixel

In digital imaging, a pixel, or pel, (picture element) is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled. Each pixel has its own address. The address of a pixel corresponds to its coordinates. Pixels are normally arranged in a two-dimensional grid, and are often represented using dots or squares. Each pixel is a sample of an original image; more samples typically provide more accurate representations of the original. The intensity of each pixel is variable. In color image systems, a color is typically represented by three or four component intensities such as red, green, and blue, or cyan, magenta, yellow, and black.

In some contexts (such as descriptions of camera sensors), the term pixel is used to refer to a single scalar element of a multi-component representation (more precisely called a photosite in the camera sensor context, although the neologism sensel is also sometimes used to describe the elements of a digital camera's sensor),while in others the term may refer to the entire set of such component intensities for a spatial position. In color systems that use chroma subsampling, the multi-component concept of a pixel can become difficult to apply, since the intensity measures for the different color components correspond to different spatial areas in a such a representation.

The word pixel is based on a contraction of pix ("pictures") and el (for "element"); similar formations with el  for "element" include the words voxel and texel.

PHOTOGRAPHY QUICK TIP – USE A TRIPOD

Tripods will ensure that your picture is free from camera shake, giving you a much sharper picture. Of course this depends on whether the tripod is sturdy and you get the focus correct.

Tripods can be quite cheap, but you will find the the cheap ones are fairly flimsy when extended to any height. It is well worth spending a bit on a good tripod as it is one of the accessories that will work with any camera and it can have a positive effect on your images.

Along with your tripod you will need a good head. Not the one on top of your shoulders, the head is the bit that connects your camera to the tripod and allows you to pivot the camera and secure it in place. Again a good quality head, whether it’s a ball and socket or pan and tilt head will be a big benefit to your photography. The last thing you want is to set your camera up for the perfect shot only to find the head slipping just as you are about to press the shutter.

There are alternatives to using a tripod, a beanbag placed on a wall or rock or some other solid object can support your camera just as well as a tripod and can be a little easier to carry, although it will still be fairly heavy. Beanbags are great for getting set up quickly as you can just chuck it on the floor, on a rock or wherever, plonk your camera down on it and start taking pictures. Tripods take a little longer to set up.

arriflex 16ST how to load film in a arri st

Aperture and Depth of Field

How to adjust the aperture

Most digital SLRs and some compacts have at least the following three shooting modes: Manual (denoted by a large M); Shutter Priority (a large S or Tv) and Aperture Priority (you've guessed it, a large A or Av). The last two of these will allow you to manually adjust the aperture. In Manual mode you will have to set both the shutter speed and aperture for an accurate exposure, while in Aperture Priority mode you only have to set the f-stop, the camera will set the shutter speed for you.
So let's assume you are in Aperture Priority mode. Where you will adjust the f-stop that is selected will depend on your camera and lens combination. For some cameras you will have to turn a ring which is right at the base of the lens, where it meets the camera's body. For others the setting on this ring will have to be at the largest number, and the actual f-stop selected via a dial or button on the camera itself. Finding the dial that adjusts the f-stop will often entail hunting around for something that changes a set of numbers on the cameras display in a seemingly irregular fashion. These will most often contain, f5.6, f8, f11, f16, f22, with one or two stops at either end of the scale.
If you are shooting in Aperture Priority mode and the selected f-stop is too large or small for the ISO setting you are on, the camera will display an error message such as "lo" or "hi". Heed this warning and adjust accordingly, or your pictures may be too light or dark. (Of course, the camera's built in light meter is fallible and in a future issue we will look at how to override it completely).

The aperture explained

In photography, aperture refers to the size of the opening in the lens of the camera through which light can pass. The size of this aperture is adjustable in nearly all the lenses that fit digital cameras. By adjusting the size of the aperture, the photographer can ensure that the correct amount of light reaches the digital sensor during any given exposure.
As such, it is one of the three elements used to provide a correctly exposed image. The others are the length of the exposure, called the shutter speed, and the light sensitivity of the sensor, called the ISO.
The aperture can be adjusted either manually or, in most cameras, automatically by the camera. When the diameter of the aperture is changed, a set of blades inside the lens narrow down or open up to allow more or less light to pass through the lens.
The act of narrowing down the aperture is often referred to as 'stopping down' while opening it up is called 'stopping up'.

Novices often find the word 'stop' connfusing, but it is easier understood when one realises that the aperture is, by convention, adjusted not over a continuum, but rather is set steps, or stops. One stop is equal to half the area of the one preceding it. So when you close down one stop, you are halving the area of the aperture, and when you open up by one stop, you are doubling it.
The stop selection dial (which selects the size of the aperture) is marked with an odd set of numbers as noted above, often starting at f5.6, followed by f8, then f11, f16 and f22. There may be one or two stops on either end of the scale. The concept works like this. The number indicates the inverted size of the aperture as it relates to the focal length of the lens. This is quite a mouthful, and not easily understood, but the point is that the larger the number, the smaller the hole, and therefore, the less light is allowed to pass through the lens. The smaller the number, the larger the hole, and the more light is allowed to be transmitted.
So, other things being equal, the brighter the light in which the picture is taken, the less light would be needed for an accurate exposure and the bigger the f-number one must use. Inversely, the dimmer the light, the bigger the hole that is needed, and the smaller the f-number that is selected.
Once you understand this, you are halfway to grasping all that is needed to become a master of the aperture.

Depth of field and the aperture

I did say halfway...
The aperture is more than just a tool used to adjust the size of the opening in a lens. It is perhaps the strongest compositional tool in the arsenal of the
photographer.
Something interesting happens when the size of the aperture is changed. When it is opened up, and

more light passes through the lens, the area which appears in focus on either side of

the distance for which the lens is focused becomes smaller.
Picture this: you are taking a portrait picture. You focus the lens on the subject's eyes. Behind him is a tree. If you set the lens at a large aperture (small number) the tree behind him will not be in focus. If you use a small aperture (large number) the tree will be in focus.
This byproduct of adjusting the size of the aperture is referred to as 'depth of field' and translates into the depth (or distance) of the area which will remain in focus for a given aperture and focus distance.
The creative utility of adjusting the depth of field should immediately be apparent. By changing how big a part of the photograph is in focus, you can control exactly which details show up, and which do not, allowing you to lead the viewer's eye anywhere you wish.

More about depth of field

The depth of field becomes greater with smaller apertures, and vice versa, that much is true, but things are a little more complicated than that.
Depth of field decreases the shorter the focusing distance, so if you are focusing on a subject that is very close to the lens, you will have less depth of field than if you are focusing on a subject which is far away.
This has tremendous consequences for macro photography and it is often very hard to even get a tiny part of the image in focus.
Further more, the depth of field for a longer lens is always less than for a shorter lens, even with the same f-stop setting and distance from the subject. So if you are shooting with a very long lens, you will be struggling for enough depth of field, more often than not.
Finally, the depth of field on either side of the point on which the lens is focused are not equal. The area further from the camera which will remain in focus for any given f-stop is larger than the area for objects nearer to the camera than this point.
There is an old photographer's maxim which says: 'Focus a third of the way in' but this is merely a guide, and as you come closer to the object, the area that remains in focus on either side of the distance for which you have set the lens, tend to converge, meaning that the area that remains in focus in front of and behind this point are closer in size.
It is also important to remember that in most cameras, the size of the aperture is not actually adjusted until the moment the photograph is taken. At the moment the shutter is released, the blades which make up the aperture swing closed to the desired setting, and the sensor is exposed to the correct amount of light.
This means that the image you see when you look in the viewfinder does not correspond to the final image. What you normally see, is what the photograph would be like if the aperture was left at its largest opening (smallest number). Most digital SLRs have a 'depth of field preview' button, which when depressed, adjusts the aperture to the required setting, which, provided that the setting is smaller than the lens' maximum, would mean that the image in the viewfinder would dim down a little and that a larger part of the image will come into focus, allowing the photographer a live preview of what the final image will look like.

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4 Rules of Composition for Landscape Photography

While I’m not always a fan of sticking strictly to the ‘rules’ or ‘guidelines’ of photography I think they can be well worth knowing and keeping in the back of your mind as you shoot (whether it’s so you can follow them or break them for effect). Here’s four ‘rules’ for landscape photography that might be helpful for those just starting out (ie they’re not meant as a definitive guide but rather a starting point) :
1. Diagonal Lines

Using diagonal lines can be a very effective way of drawing the eye of those viewing an image into it and to the main focal point.
The ‘lines’ need not be actual lines – they could be the shape of a path, a line of trees, a fence, river or any other feature in an image.
Converging lines (two or more lines coming from different parts of an image to a single point) can be all the more effective.



2. Geometric Shapes

By positioning key aspects of a landscape on points of a geometric shape you can help create a balanced composition. Perhaps the most common and easiest way to do this is to use a ‘triangle’ shape between objects in an image with three objects in a frame positioned with one to each side and one more central.
Using Geometric Shapes in this way isn’t something that I’ve done a lot of – but it is one technique to get balance in a shot and if you’re clever, to lead the eye into it (in a similar way to the diagonal lines rule above).
You can see this illustrated (to a point) in the photomontage image to the right.

3. The Rule of Thirds

The Rule of Thirds gets trotted out more often than any other in all types of photography and is one of the first rules of composition taught to most photography students. While sometimes it can feel a little cliche it can also be a very effective technique in landscapes (although keep in mind that breaking this (and other rules) can also produce dramatic and interesting shots).
Position key points of interest in a landscape on the intersecting point between imaginary ‘third’ points in an image and you’ll help give your image balance and help those focal points to really capture attention.

4. Framing Images

While adding points of interest to a foreground is an important technique for adding interest to landscape shots – a similar technique is to ‘frame’ the shot by adding interest to other parts of the edges of an image.
Perhaps the most common way of framing a landscape shot is to include an overhanging branch in the upper section of a shot. Similarly framing a shot with a bridge might work.

Rules are Made to Be Broken?

Of course while knowing the rules can be important – knowing when to use them and when to break them is a talent that great photographers generally have.
Practice these techniques – but don’t get so worked up about them that they kill the creativity that you have.
Let me finish with a quote about Rules of Photography from Photographer Edward Weston to help give us a little balance on the topic:
“To consult the rules of composition before making a picture is a little like consulting the law of gravitation before going for a walk. Such rules and laws are deduced from the accomplished fact; they are the products of reflection.”

Tips For Macro Photography – The Extreme Close-Up

Marco photography has always fascinated me because practitioners of the art/craft continually amaze me with the small details of our gigantic world. Much like a Seinfeld bit, Macro photography typically consists of finding an everyday object and photographing it at such close proximity that the perhaps mundane — now taken out of context — is startling and interest-piquing. Marco photography can be extra enjoyable and elucidating, as you’ll be pleasantly surprised by the myriad of minute details your camera records. Icicles hanging on a tree branch or side of house can become surreal when viewed through macro photography.

Avoid Camera Shake

When you shoot Macro, your Depth of Field is extremely shallow, so critical focus is paramount to get a more than good shot. And what’s the main culprit for soft focus in marco photography? You guessed it, camera shake. To avoid camera shake you’ll need to shoot at a higher shutter speed, use a tripod and/or a cable release. Also, never, never, never use the Auto Focus setting when doing Macro photography, because the computer can easily be tricked (not that it matters if you have a huge memory card, but why waste the time?). By manually focusing your lens, you have precision control of what tiny – but now huge – details will be the center of attention.

Composition

With macro photography, you can (and should) take your time to get the composition precisely perfect (or perfect for what you envision), so don’t hesitate to move up, down and all around the subject of your gaze. Unless you’re shooting a bumblebee or a humming bird, you have no time constraint, so using bracketing to get the best exposure to match the flawless composition. Bracketing, if you didn’t know, is taking at least three of the exact same photographer at different exposures (over, neutral and under) to get color accuracy & vibrancy, shadow & highlight detail and depth of field that you can compare and make the most dynamic selection.

Checklist

Here are some quick things to remember, sort of a checklist, for macro photography:
1. Simplify your image as much as possible.
2. Fill as much of the frame as possible with your subject.
3. Over-compensate for sharp focus.
4. Experiment with various angles to find the most aesthetically pleasing.
5. Be very aware of the background (which will be out of focus) and eliminate anything that will be distracting.
Macro photographs show you details of the world that are more often than not overlooked, because even the simplest subject can seem more than important and poignant when its surface details are being examined at such a high magnification. Remember, by looking closer – borrowing a phrase from American Beauty — you’ll see that you have a whole new array of subjects to photograph.