What is in a file format?
All files have extensions that tell us what they are. In photography file format types tend to be either compressed, lossy files (*.jpg, *.GIF, *.PNG files etc.) or RAW files (CR2, NEF, TIFF etc). Actually these are both of the same generic file type – Bit Maps or Raster Images.
File format types – Vector images
The vector file format types are useful for creating precise diagrams. The lines and shapes are each produced with editing tools that make mathematical models for them. The pixels which display the lines are under the control of the math-models and display colours (black, white, red etc) so you see the shapes they make. The diagram is precise, crisp and clean.
The precision, measurement and scalability of the model comes from the predictable formulae. However, to save the file for use on the Internet requires another of the File format types. Vector files need to be converted to raster files.
File format types – Raster images
The mathematical-model type of diagram is more difficult to produce in an image editor for processing photographic files. For photo edits we use an image editor for painting, cloning and shading and erasing and so on. These types of image editors create what is known as a raster image or bitmap image. These raster images use file format types suited to art, free hand drawing/painting and image processing.
The raster files are ‘bitmaps‘. These are created from arrays of sensors. Each tiny sensor spot on our cameras’ digital image sensor is a ‘photosite‘. It’s a collection point of data (bits of data) for the light coming into the camera. There are millions of these sensors (mega-pixels of them).
Add up all that data and display it on a screen and the pixels on the screen show us an image (a bitmap). Each tiny bit of data collected at a photosite is translated to a bit of data that represents it on screen in a pixel. The image reproduces the real world.
Editors can do both raster and vector processing
The two file format types, ‘raster’ and ‘vector’, are not inter-changeable. They have to be converted from one to the other. This needs to be done using one of the tools in the editor you are using. It may mean saving the file in the new format and then re-opening it. It may need to be re-opened in another editor for further editing.
Some editors can create both File format types. But the two types of image data need to be kept separated. In most editors this is done by creating “layers” for each format type. Some layers form vector lines and graphical objects. In other layers the data the makes up raster objects. This means they can retain the special properties that make them useful. For example, precise lines in vectors and, say, variable hue/tone for brush strokes in a raster image.
Mixed editing allows us to do artistic work or process photos. And, within the same image, we can put in precise graphical and geometric components.
In the final display…
In the end both file format types give up most of their editing properties. The full format of each type tends to have very large files. Too large to use easily on the Internet. When we save these files for display we reduce the editing ability. This reduces the file size.
In vector files we “rasterize” the vector components to convert to image files. These in may still be too big for Internet use. They may need to be made smaller.
Raster files in full format can be reduced by taking out a lot of editable data in the file. That reduction (compression) makes them easier to use on the Internet. So in the end the file format becomes the *.jpg, *.GIF, *.PNG files etc. that we know so well. The reduced data means the new format, (eg. *.jpg) is not easily edited without affecting the visible quality of the image.
If all this seems a little technical think of it this way…
A spread sheet program is suited to doing maths, processing numbers and doing statistics. On the other hand a word processor is suited to writing text, manipulating words, using natural language and laying out pages. Both use numbers and letters. Both use mathematical tools and writing tools.
The unique forms of the word processor and spread sheet make each suitable to a particular purpose. A spread sheet works in a mathematical way (with some wordage). Word processors are more about language but use of number when needed.
Vector graphics and raster graphics have almost the same distinctions. They do it with art (in say, ‘PhotoShop’) and draughtsmanship (in say, ‘Illustrator’ or other draughting or drawing editor). Spread sheets and word processors have their own file format types too.
Glossary entries about file format types
Entries in our Glossary explain file format types in more detail…
Definition: Raster Image :: artistic and photographic images.
Definition: Vector Image :: precise diagrams, graphs and geometric pictures.
Rastor images vs. Vector images – a comparison table.
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