Pixel, Megapixel and Resolutions.

The first number you see in a digital camera description is its megapixels rating. A pixel (short for picture element) is one tiny colored dot, one of the thousands or millions that compose a single digital photograph. (1 megapixels = one million pixels.) This term is one thing you cannot avoid to at least hear of, since pixels are everything in computer graphics. The number of megapixels your camera has determines the quality of your pictures’ resolution (the amount of detail that appears). The higher the megapixel rating on a camera the better the resolution is. A 5-megapixels camera, for example, has better resolution than a 3-megapixels one. It also costs more. How many of those pixels you actually need depend on how you’re going to display the images you shoot.

If Your Pictures Only for Computer

Many digital photos never get further than a computer screen. After you transfer them to your computer, you can distribute the images by email, post them on a Web page, or use them as desktop pictures or screen savers.

If such activities are the extent of your digital photography ambition, you can get by with very few megapixels. Even a $100, 2-megapixels camera produces a 1600 x 1200-pixel image, which is already too big to fit on the typical 1024 x 768pixel laptop screen (without zooming or scrolling).

Getting Down Further, For Printing Purposes

If you intend to print your photos, however, your megapixels needs are considerably greater. The typical computer screen is a fairly low-resolution device: most pack in somewhere between 72 and 96 pixels per inch. But for a printed digital photo to look as clear and smooth as a real photograph, the colored dots must be much closer together on the paper150 pixels per inch or more.

Remember the 2-megapixels photo that would spill off the edges of a laptop screen? Its resolution (measured in dots per inch) is only adequate for a 5 x 7 print. Enlarge it anymore, and the dots become visible specks. Your family and friends will look like they have some unfortunate skin disorder. If you want to make prints of your photos (as most folks do), keep the following table in mind:

Megapixels	Pixel Resolution	Print Size @300 ppi	Print size @ 200 ppi	Print size @ 150 ppi
3	2048 x 1536	6.82″ x 5.12″	10.24″ x 7.68″	13.65″ x 10.24″
4	2464 x 1632	8.21″ x 5.44″	12.32″ x 8.16″	16.42″ x 10.88″
6	3008 x 2000	10.02″ x 6.67″	15.04″ x 10.00″	20.05″ x 13.34″
8	3264 x 2448	10.88″ x 8.16″	16.32″ x 12.24″	21.76″ x 16.32″
10	3872 x 2592	12.91″ x 8.64″	19.36″ x 12.96″	25.81″ x 17.28″
12	4290 x 2800	14.30″ x 9.34″	21.45″ x 14.00″	28.60″ x 18.67″
16	4920 x 3264	16.40″ x 10.88″	24.60″ x 16.32″	32.80″ x 21.76″
35mm film scanned	5380 x 3620	17.93″ x 12.06″	26.90″ x 18.10″	35.87″ x 24.13″

These are extremely crude guidelines, by the way. Many factors contribute to the quality of an 8 x 10 print including lens quality, file compression, exposure, camera shake, paper quality, and the number of different color cartridges your printer has, among other things. You may be able to print larger sizes than those listed here and be perfectly happy with them. But these figures provide a rough guide to getting the highest quality prints.

Cropping

The other important advantage that a camera with multiple megapixels gives you is the ability to create high-quality prints of select portions of your photo. Say you’ve taken a great shot of your kids, but they occupy just a smidgen of the overall picture. No problem if your camera’s got a lot of megapixels under the hood. Just crop out all the boring background and keep just the juicy parts. If you try that same maneuver with a picture that comes from a 2 megapixel camera, you’ll end up with a photo filled with unsightly pixels.

Exposure

In photography, exposure is the total amount of light allowed to fall on the photographic medium (photographic film or image sensor) during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance.

Exposure time is controlled in a camera by shutter speed and the illumination level by the lens aperture. Slower shutter speeds (exposing the medium for a longer period of time) and greater lens apertures (admitting more light) produce greater exposures.An approximately correct exposure will be obtained on a sunny day using ISO 100 film, an aperture of f/16 and a shutter speed of 1/100th of a second. This is called the sunny 16 rule: at an aperture of f/16 on a sunny day, a suitable shutter speed will be one over the film speed (or closest equivalent).

Ultimately there is no such thing as “correct exposure”, as a scene can be exposed in many ways, depending on the desired effect a photographer wishes to convey.

SLR

Definition: Standing for single-lens reflex, these are higher-end digital cameras revered by serious photographers. The digital versions of SLRs work in this manner: the shutter retracts so an image can be recorded. One of the prime benefits of using a digital SLR camera is that lenses are interchangeable.

Also Known As: digital SLR, single-lens reflex, digital SLR camera

Examples: I decided to buy the latest SLR so that I can change out lenses on my camera

Canon EOS Rebel - XTi is a beginner level Digital SLR sold under $1000.

Optical Zoom

Definition: This is a type of zoom on digital cameras that replicates what a 35mm zoom does, by actually magnifying the subject of the photo.

 

Examples: The optical zoom lens produces a better quality image than the alternative digital zoom

Megapixel

Definition: One-million pixels, a unit of measurement in an image. This number will determine the quality of the image. Think of it as the number of dots in your picture. A low density of dots will result in a poor image.

Examples: Images from my one megapixel camera will really only look good in an email, but I get great enlargements from my five megapixel camera.

 

F-Stop

Definition: This is the number assigned to determine the aperture, or size of the lens opening. A high f-stop number means a small amount of light is allowed in, which would be used to avoid an overexposed image. A low f-stop number means a large amount of light is let in, as you might use to shoot at a high shutter speed without getting a dark image.

 

Examples: I used a high f-stop setting to avoid my image being too bright and sunwashed.

 

The f-number f/#, often notated as N, is given by

where f is the focal length, and D is the diameter of the entrance pupil.

Digital Zoom

Definition: Enlarging of an image that requires the camera to double the size of the pixels. Due to the doubling of pixels the image begins to become fuzzier and fuzzier as you enlarge.

 

Examples: I try to avoid using digital zoom because the image suffers.

CCD

Definition: In essence, this is the electronic version of film for a digital camera. Standing for charged coupled device, this refers to the chip used to record image information. Light hits the CCD when a photo is taken, and then the analog CCD converts the information to digital. This is one of the two main recording devices used in digital cameras.

 

Examples: The CCD on my digital camera is what records the images when I shoot a picture.

 

Photography at A Glance

Photography has become pervasive in our society. Each of us sees hundreds, if not thousands, of images every day. The vast majority of images are those taken for personal enjoyment. These images either capture the moment or provide a form of self-expression. Many other images are used to lubricate the wheels of commerce. They appear in ads and on magazine covers and packages. Other images in magazines and newspapers are used to convey news or to make an editorial point. No matter what purpose images are put to, it is the images themselves that are transcendent. The way they have been captured is secondary. However, changes in technology can open new opportunities and approaches that change the way images look.

For example, the introduction of the 35mm Leica back in the 1930s made it easier to capture fast moving action and images became more spontaneous and fluid, a far cry from the more formally posed images required by much larger and more ackward cameras.

The vast majority of the images you see are still captured with traditional cameras and film. However, this is changing rapidly as digital cameras are accepted in more and more areas of photography. Already they have made major inroads into catalog photography and photojournalism. They are now well on their way to becoming a major factor in photography for self-expression. In time, they are destined to dominate photography.

Although photographic technology has changed dramatically since its invention in 1840, the principles of good images have remained fairly constant. The images taken in 1840 by Henry Fox Talbot and Daguarre are as well composed and interesting as any images taken with the most modern equipment. However, although technology doesn’t make good images any easier to capture, it has made profound changes in others areas of photography. Digital photography in particular has made it possible to capture an image and then instantly distribute it around the world. Digital photography has also closed the darkroom and opened up an entirely new way to edit and present images. A digital camera, a notebook computer, and a high-speed Internet connection makes each of us a node on an ever-expanding network of photographers and viewers.

The speed at which the current change is happening is almost frightening, for it means that photographers constantly have to adapt to new technology. What stops this transition from being completely terrifying is the payoff in increased capability. Yes, photographers have to work harder to keep abreast of changes in equipment, but at least you’re rewarded with superior performance. Although film photography diehards bemoan the impact that digital has had on the medium, the reality is that digital photography has rekindled interest in photography for many people. Even better, in the hands of dedicated users, the technology provides incredible potential for learning and improvement. The ability to review an image immediately after its creation while there is time to analyze it and improve upon it is immensely valuable. This alone is worth the price of admission.

Barely a decade after they first entered the average consumer’s consciousness (and price range), digital cameras started outselling film camerasa shift of culture-jarring proportions. By early 2006, a staggering 92 percent of cameras sold were digital cameras. Film photography giants like Nikon, Canon, and Olympus are now major players on the digital market, and they’ve been joined by manufacturers coming from the electronics side, like Sony, HP, Casio, and Samsung. The makers compete for your dollars by offering dozens of digital camera models with a dizzying array of features. Fortunately, if you understand just a few important digital camera basics, you can evaluate and take great photos with almost any camera you pick up.

 

Aperture

Definition:

The size of the lens opening, which regulates how much light passes through the lens to hit the CCD. Aperture is measured in f-stops. A higher number equals a smaller amount of light. Some digital cameras (such as digital SLR cameras) allow a user to manually adjust the aperture setting.

 

Examples:

Since I was using a fast shutter speed, I used a larger aperture to get sufficient light.

 

 

The difference of aperture setting: f/32 - narrow aperture (left) and f/5 - wide aperture (right)

Aperture Area:

The amount of light captured by a lens is proportional to the area of the aperture, equal to:

Where f is focal length and N is the f-number you set in the camera.