Why do they have to make things so complicated by throwing in words like megapixels!
It's not as bad as it sounds though - basically the higher the number, the better the quality of photos you can expect.
One megapixel = One million pixels
Pixel is a single point in a graphic image. Graphics monitors display pictures by dividing the display screen into thousands (or millions) of pixels, arranged in rows and columns . The pixels are so close together that they appear connected.
The chip inside the Digital Camera is responsible for the number of MegaPixels.
A 2 megapixel point-and-shoot camera is fine for holiday snaps and will allow you to print up to 5 by 7 inches but you should look to go to at least 4 megapixels for 8 by 10 inch prints.
The "effective" megapixel number quoted for cameras is the number you are looking for here.
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ZOOM
With zoom you can switch between close up and a faraway point. There is a very important thing to think about when buying a camera and that is the difference between optical and digital zoom.
Optical zoom lens
An optical zoom is a true zoom. Its focal length actually extends and retracts. An image is magnified by the lens itself. An optical zoom produces the best quality images.
A zoom lens is used to magnify an image 3X, 4X, 10X and more. If you want to zoom in close to distant objects, buy a camera with the longestzoom you can afford. Very long zooms are prone to camera shake , particularly in low light. To help prevent this, some digital cameras have image stabilization.
Digital zoom lens
A digital zoom is not a true zoom. It is a simulated zoom that enlarges the central portion of an image. The actual length of the lens does not change. A digital zoom pre-crops the center area of an image. Resolution is reduced, giving the appearance of zooming in. It is similar cropping with photo editing software . A digital camera may have an option to turn off the digital zoom.
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Movie Mode
Many cameras now offer a movie mode which allows you to capture short video clips.
Beware though as although these can be great fun the quality is never anywhere near as good as a camcorder.
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Picture Modes
Most digital cameras now come with a whole host of Picture Modes which allow you to do such things as take portraits, night shots, close up "macro" shots, etc.
As you get used to the camera and digital photography in general you may well find your self using some or all of these so they are worth considering.
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Memory Cards
Digital camera storage/memory cards are digital camera film, that's where the digital camera stores photos you take. The advantage is of course you can use them over and over again and a lot more photos can be stored (depending of course on the capacity of the card).
Most cameras now take some sort of memory card. This is the digital equivalent of film and allows you to store images on a removable card that you can plug straight into a card reader on a PC or photo printer .
There are numerous types of card available including Compact Flash (CF), XD Picture Card , Secure Digital (SD), Smart Media or Multimedia Card (MMC) memory.
You should budget for getting a larger capacity card (128MB or 256MB) than the one that comes with your camera (if you get one at all). Just make sure you get the correct type as others will not be compatible.
You can buy brand name memory cards or cheaper, generic ones however again you get what you pay for. The generic ones will work fine but may have a slower data transfer rate which means there may be a delay between taking shots with your camera. Fine if you subject is sitting in front of you with a cheesy grin but not much use if you are trying to get an action shot of little Johnny doing the 100m sprint on Sports Day!
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Liquid Crystal Display (LCD) Monitor
The screen on the back of a digital camera, known as a LCD monitor , can be used to frame shots instead of a viewfinder . In fact, with the improved visibility and size of LCDs the last few years, some digital cameras no longer have viewfinders. The LCD is also used to preview images right after they are taken, to view menus and settings and to review recorded images when the camera is in play mode.
LCDs display a 100% view of a framed shot. It can not be depended on for complete color accuracy and it can be difficult to view in bright light. To help compensate, the brightness and contrast of an LCD can be adjusted. LCD hoods are available that reduce glare and help improve the visibility of the monitor in outside lighting.
Some digital cameras have "articulating" LCDs that can be swiveled and tilted in various directions. They are useful macro photography and for framing shots taken at difficult angles.
A LCD consumes a lot of battery power so there is usually a power saving function. The LCD can be programmed to shut off automatically after a specified period of time.
LCD sizes:
The wide-spread LCD size is 1.8", but there are numerous of smaller and bigger LCD size like:
1.5"
1.8"
2"
2.2"
2.5"
2.8"
3"
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AF System
An Autofocus Assist Lamp assists a digital camera focus when taking photos in low-light. The lamp is usually positioned near the lens barrel. When the shutter-release button is depressed half-way, a light beams from the camera to illuminate an area where the camera focuses on the subject. Use an AF Assist Lamp within the recommended range, which varies between cameras.
Some digital cameras have an infrared AF Assist lamp . Because infrared light is invisible, a subject won't be startled as they may be by a visible light.
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Flash
For most indoor photography, where there is relatively little ambient light, you either need to expose the film for a longer period of time or momentarily increase the light level to get a clear picture. Increasing the exposure time doesn't work well for most subjects, because any quick motion, including the movement of the camera itself, makes for a blurry picture.
Electronic flashes are a simple, cheap solution to this inherent problemin photography. Their sole purpose is to emit a short burst of bright light when you release the shutter. This illuminates the room for the fraction of a second the film is exposed.
In this article, we'll find out exactly how these devices carry out this important task. As we'll see, a standard camera flash is a great demonstration of how basic electronic components can work together in a simple circuit.
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Self timer
The self timer allows the camera to take a picture unattended. With it you can take a picture of yourself. Once the timer is set, you usually have about ten seconds to get into the picture. A flashing light or a tone signals when the picture is about to be taken.
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Interface
Once you've got the images stored in your camera on the memory card you need a way to get them into your computer! There are several ways to connect digital cameras to a PC as well as external card readers.
Serial - The earliest digital cameras had a serial interface, but no current cameras use this since it is so slow
USB 1.1 - USB was the first widespread high speed method of data transfer from cameras. It is theoretically capable of transfer speeds up to 11 megabits/second (note mega bits not mega bytes )
USB 2.0 - A development of USB but much faster - up to 480 megabits/second. USB devices are compatible with USB1.1 ports on a PC, but will only work with them at the lower data rate.
IEEE 1394 (Firewire) - Though this is an older interface than USB, it was originally only really used much on Apple computers. It's capable of high speed transfer (400 megabits/second) and it's now found on some PCs or it can be added to them via a plug-in card. More common on digital video cameras than still digital cameras.
Just about all cameras can connect to a PC, but it's sometimes easier to remove the memory card from the camera and insert it into a dedicated card reader. Even if your camera only has USB 1.1. if your computer has a USB 2.0 you can use a USB 2.0 card reader for faster transfer. Card readers are cheap, anywhere from $15 to $40.
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Battery
The main issue with digital cameras is battery life.
Lithium batteries will tend to last longer but rechargeable NIMH (nickel metal hydride) are the next best thing.
Make sure the camera comes with a battery charger and buy a few spares and keep them charged if you plan to use your camera a lot.
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Aspect Ratio
The aspect ratio of a camera is the ratio of the length of the sides of the images. For example, a traditional 35mm film frame is approximately 36mm wide and 24mm HIGH. This has an aspect ratio of 36:24, which can equally well be expressed as 3:2. Some digicams use the same aspect ratio for their digital images. For example most digital SLR (single lens reflex) cameras have a 3:2 aspect ratio. However, video monitors typically use a 4:3 aspect ratio. For example a monitor with a 800x600 display has a 4:3 aspect ratio. With this in mind, most consumer level digicams use a 4:3 aspect ratio for their images.
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Sensor Size
The size of the digital sensor element (which is equivalent to the size of the negative for film cameras) is pretty small in all consumer digicams - typically around the size of a fingernail (and a small fingernail at that!). As I said above, a 35mm film frame is 24mm high by 36mm wide but most digital cameras use sensors very much smaller than this. Here are some typical digicam sensor sizes. The "name" of the sensor is based on specification for old TV tubes used in the 1950s. Nobody is quite sure why it's being used for modern digital sensors since the "sizes" don't really relate in any consistent way to the actual physical size of the sensor. However these names are widely used, so it's best to know what they are. They are often listed in digital camera spec sheets.
"Name"
Aspect Ratio
Width (mm)
Height (mm)
1/3.6"
4:3
4.0
3.0
1/3.2"
4:3
4.5
3.4
1/3"
4:3
4.8
3.6
1/2.7"
4:3
5.3
4.0
1/2"
4:3
6.4
4.8
1/1.8"
4:3
7.2
5.3
2/3"
4:3
8.8
6.6
1"
4:3
12.8
9.6
4/3"
4:3
18.0
13.5
EOS 10D
3:2
22.0
15.0
Most of the current small 5MP digital cameras use 1/1.8" sensors which are about 7mm x 5mm. They have an area 25x smaller than 35mm film and about 9.5x smaller than a small sensor digital SLR like the Canon EOS 10D. You might wonder why sensor size matters and that's a pretty complex issue. The bottom line is that, for a given pixel count, the larger the sensor (and hence the larger the area of the individual pixels) the better the image quality and the lower the noise level. While large sensor cameras like the EOS 10D can operate at the equivalent of ISO 3200 (though the image does get noisy), many consumer digicams with small sensors cannot operate above ISO 400 before the noise becomes excessive.
Another factor in quality here is that small sensors tend to be of a different type than large sensors. Small sensors, and the sensors used on all consumer digital cameras, use a scheme which can read the data from the sensor in real time using a scheme called " interline transfer " and the CCD electronics control exposure rather than a mechanical shutter. Large sensors used on more expensive Digital SLRs are often of a different design known as full frame - which doesn't refer to their size, but their design - and which require the use of a mechanical shutter. They don't read out and the display the data in real time, only after the exposure so they can't give real time LCD displays or record video. The advantage of this scheme is that the whole pixel area can be used to capture light while interline transfer CCDs use part of each pixels to store charge. Since smaller pixel areas generate more noise and interline transfer CCDs are not only smaller to start with but use some of their pixel area for charge storage, their noise level is significantly higher. So the smaller interline transfer sensors in consumer digital cameras yield lower quality images than those used in higher end DSLRs, they can do more "tricks" like recording video clips and giving a live image display on their LCD screen. The lack of a mechanical shutter also makes the cameras cheaper and simplifies construction.
Small sensors mean that short focal length lenses are needed to give the same field of view as cameras using larger sensors or 35mm film. So, for example, a typical consumer digicam may need a 7mm lens to give the same view as you would get using a 35mm focal length lens on a 35mm camera. This has consequences on depth of field and means that most consumer digicams have a vary large depth of field. Great if you want everything in focus, not so great if you want a blurred background.
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White Balance
With film you can buy "daylight balanced film" for shooting outdoors or "tungsten balanced film" for shooting indoors under normal domestic lighting (not fluorescents!). If you use daylight film under tungsten light the images will be very yellow. If you use tungsten film in daylight the images will be very blue. With film you have to correct for the "color temperature" of the light using filters or by the right choice of film.
With digital you can pick your white balance to suit your light source, so that white looks white, not yellow or blue. Normally there is an automatic setting and the camera decides what white balance setting to use. However if you know what your light source is you can usually set the camera to it and this may give better results. Most digital cameras have settings for sunlight, shade, electronic flash, fluorescent lighting and tungsten lighting . Some have a manual or custom setting where you point the camera at a white card and let the camera figure out what setting to use to make it white.
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Sensitivity
Sensitivity settings on digital cameras are the equivalent of ISO ratings on film. Just about every digital camera will have settings with a sensitivity equivalent to ISO 100 film and ISO 200 film. Many will have an ISO 400 setting, but above that the images from cameras with small sensors gets pretty noisy. The more expensive digital SLRs with much larger sensors have much higher sensitivity settings. At ISO 400 they are virtually noise free and some can go as high as ISO 3200 or even ISO 6400! Very few cameras have ISO setting lower than ISO 100 because noise levels are so low at ISO 100 there would be no real advantage in a slower setting. Quite a few digital cameras have an "auto" ISO setting, where the camera will pick from ISO 100, ISO 200 and sometimes ISO 400, depending on the light level and the mode in which the camera is operating.
