The zoom effect in a digital camera is similar to, yet different, from that of a conventional camera. In a conventional camera the zoom effect is the result of optics. It brings distant subjects closer.
However, in a digital camera there are two kinds of ‘zooms’. The first is similar to that of a conventional camera and is known as the optical zoom. The second is the digital zoom, and is more interesting. It ‘simulates’ optical zoom by enlarging a portion of the image — that is the digital zoom selects a portion of the photograph and blows it up.
The zoom effect should not be confused with photo editing, where an image editing software is used to crop and blow a picture on a computer screen. Another misconception associated with digital zoom is that it is very handy in capturing long distance images. Nothing can be more misleading. It is optical zoom that matters more in a digital camera.
In fact, today the digital camera manufacturers have started using a new term – total zoom. This term only confuses the customer for there is nothing like total zoom. At best, it can be used to indicate the fact that a digital camera has both kinds of zoom – optical zoom and digital zoom.
Another zoom effect that has been developed recently is the “smart zoom”. This zoom maintains the image quality by avoiding interpolation of the image. However, smart zoom works only if you select an image smaller than the full available image size.
The zoom that should be used for comparing cameras is optical zoom, and not digital zoom or total zoom. A camera’s quality depends upon the value of optical zoom; a camera with higher optical zoom is better than a camera with lower optical zoom.
Sometimes optical zoom is compared to resolution while buying a digital camera. Nothing can be more absurd. These are two different values and have no common link. Resolution is used to indicate the number of pixels in an image while optical zoom is used to define the lens power. It can neither increase nor decrease the resolution.
There is also a tendency today to disable digital zoom. Some photographers prefer to crop and enlarge an image on a computer screen. They don’t trust the camera to do it for them. This is not a good practice because it reduces the effectiveness of your camera.
The following terms are used in digital photography:
Aperture: The opening that lets light travel to the camera’s interior where the sensor is placed.
Digital zoom: The process of blowing up a part of the picture. This function that is performed within the digital camera leads to a loss of picture quality.
JPEG: The term used to describe the compression of a digital image. This compression ratio was fixed by the Joint Photo Experts Group to reduce the picture size. However, the reduction leads to a considerable loss of picture quality.
Megapixels: An image that is made up of one million pixels.
Memory: The storage space provided within digital cameras to store pictures.
1 MP camera: This is a camera that can shoot an image which is made up of one million pixels.
Optical Zoom: This is used to change the focal length and magnification of the lens.
Pixels: It is a contraction of the term PIcture Element with a numerical value between 0 and 255. Each pixel is made up of three color channels.
Pixel Count: This is the number of pixels that go into making each image.
PPI: This is the acronym of pixels per inch, and is used to describe the picture quality. The higher the number of pixels per inch the better is the picture.
RAW/NEF: This is an uncompressed image as shot by the camera. The RAW picture format has been introduced by Canon. Nikon calls this format as NEF.
Sensor: The digital strip that receives light. It performs the same role that the negative does in the conventional camera.
Shutter Speed: The duration for which the camera’s aperture opens to allow the light to stream in.
TIFF: This is the short form of Tagged Image File Format. There is no loss of information in this format. But the file sizes are very large.
White Balance: The setting used to ensure white light. A digital camera normally has settings for sunlight, shade, electronic flash, fluorescent lighting and tungsten lighting. You need to adjust them before shooting.
