Noise

In digital photography terminology, noise is the digital equivalent of film grain. It shows up on digital photographs as small coloured blotches, usually in the darker areas of an image. Noise often goes overlooked in snapshots, but becomes very obvious if enlargements are made.

Noise is worse in digital photos taken in low light. It can be removed to some extent by software, but a better quality digital camera will usually produce less noise in the first place.

Whereas film grain can add atmosphere to a photograph, digital noise is generally considered to be unattractive. Digital photographers looking for a “grainy” effect aim to start with a clean image (i.e. free from digital noise), and then add the grain effect afterwards using software.

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Sensor

The electronic chip that records the image in a digital camera. They come in two main types. CCD (Charge-Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) are the most common. CCDs are used almost exclusively in compact cameras, CMOS sensors are used in larger, and more expensive DSLRs.

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Pixel

A small dot in a digital photography image. Thousands of pixels make up a digital photograph.

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TIFF 

In digital photography terminology a TIFF is a type of lossless file format. Stands for Tagged Image File Format. Because they are lossless files the image data is stored whole (nothing is thrown away*). This results in large file sizes, but also good quality photographs.
* TIFFs can be compressed to save space, but not as much as JPEGs. When they are un-compressed the software reverses the original compression process; the original large file is the result.

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Resolution

In digital photography terminology, resolution is a measure of the number of pixels there are on a sensor. The resolution of digital cameras is measured in “megapixels” – millions of pixels. It works by a simple bit of maths – multiply the number of pixels along the bottom of the sensor by those up the side. For example, a sensor with 3000 pixels along the bottom, and 2000 up the side equals 6,000,000 pixels in total. That would make it a 6 megapixel camera.

Theoretically it is possible to change the sensor in a digital camera (say, to upgrade a 5 megapixel sensor to a 10 megapixel sensor). In practice though, so much of the camera would have to be replaced it makes this impossible to do.

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RAW

RAW files are the actual data taken directly from a digital camera’s image sensor. They have not been processed by the camera at all. This means they are the purest image file possible in digital photography. Often, quite correctly, the terminology “digital negative” is used to describe them.

Different camera manufacturers have different names for their own RAW files. For example, Canon uses the digital photography terminology “RAW”, Nikon uses different digital photography terminology – “NEF”. They are incompatible with each other. Whereas every computer can show JPEG images, RAW files need specific software. This is always supplied by the manufacturer when you purchase a digital camera. It is also easy to obtain on the internet too.

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JPEG 

In digital photography terminology, JPEG is a type of lossy file format. Stands for Joint Photographic Experts Group. It is the most common file format used in digital photography. When the image is saved, the camera strips out data (parts of the photo) that the human eye probably won’t notice. This is called “compressing” the file. It keeps the size of the file down so that more images can be stored on the camera’s memory card.
The level of compression is set by the photographer and will affect image quality. The more the image is compressed, the more data is thrown away (and a small file size is the result). Less compression = less data thrown away = larger file size.

jpeg
The danger is that if a file is compressed too much (i.e. lots of data is thrown away), the quality of the image suffers. The photos look “blocky” and “pixelated”.
On digital cameras the highest quality setting (usually called “Best” or “Fine”) results in less data being lost, and a good quality image is produced. The lowest settings (usually called “Low” or “Economy”) results in more data being lost, and a poor quality image is produced.

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Lossy (Lossless files)

When a digital camera takes a photo, the image data is stored on a memory card as a computer file. If the data is stored fully, the file is called a lossless file. These files are quite large in size. The most common type of lossless file in use are TIFFs.
To cut down on large file sizes, the camera can throw away parts of the data that the human eye probably won’t notice anyway. These files are called lossy. The most common type of lossy file are JPEGs. Caution should be taken when using JPEGs if image quality is important.
NB: mp3 music files work in a similar way. The original, complete music file, is stripped down leaving only the bits that the human ear is sensitive to left behind.

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File

In film photography photos are recorded onto light sensitive film. This is developed with special chemicals and a negative is produced. In digital photography photos are stored as a digital file. You need to decode the file in order to view it. There are different types of file formats used in digital photography. Some are lossy and some are lossless. The most common lossy file format used in digital photography is JPEG. The most common lossless file format used is TIFF. Increasingly becoming common are lossless RAW files.

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DSLR

Stands for Digital Single Lens Reflex. This is the digital equivalent of a SLR camera. The difference between this and a traditional SLR is that a DSLR doesn’t need film. The photograph is recorded on a digital image sensor and saved onto a memory card.

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