This page is a simple introduction to some digital photography basics, designed to give "newbies" some starter information.
People new to digital photography seem to get all sorts of confusing advice about what file types they should use in their camera and to further process on the computer. Some information you may get can be correct, some misleading and some just a waste of space. The trouble is that it is you who has to do the hard work to find out what is best for you. Here's a few words that may help your decision. There's many file types out there but the following list does seem to cover most situations for cameras.
JPEG or JPG files ("jay peg") are the most likely file type to meet in any camera. The advantage is that the file type can be quite small for the image information it may contain. The disadvantage is that selecting too high a compression factor (and too small a file) will start destroying the image.
Often cameras will provide maybe 3 different JPEG file compression rates, in most cases the name may be obvious as to the quality expected. "Fine" or "SHQ" or "best" or some name like that will give the biggest JPEG file and the best quality. The camera often comes with a default setting of some middle level of quality and compression. This middle setting is usually quite OK if just wanting to print postcard size for the family album. If wanting to print larger to maybe 8"x10" size then that compression level may exhibit problems in the print. Selecting a less compressed mode and a larger JPEG file size will help overcome that problem, but at the expense of less images per memory card.
You can put an empty memory card in the camera and then select all the different file types one by one and the LCD (or sometimes viewfinder) will usually show the number of shots remaining, that is, approximately how many shots of that type you will get on that card. Make sure though that you are always using the highest resolution as lowering the resolution (the number of megapixels output) can also make files smaller, but then only suitable for smaller print sizes.
So JPEG files are convenient in that they usually can fit quite a few onto a memory card and take less time to write to the memory card and to transfer to the computer. The bigger problem starts in the computer if you decide to further improve and manipulate that JPEG image. Each time a JPEG file is read from the disk, altered in some way, and written back to the disk, it gets re-compressed again. Each re-compression will lead to further loss of image detail, like copying a video tape to a video tape, it gets worse as you go further. This effect can be lessened by choosing a high quality JPEG with very low compression at file re-write time - there's usually an 'options' button in the photo edit software that helps you there at write time. Or you can choose to save the file in some other format that doesn't hurt the data any further. See TIFF.
TIFF or TIF files do not compress the data at all, every pixel has the full information in it for all colours, so the file size can be quite big which means less images per memory card and much longer write times to card and read times when transferring to the computer later. For all normal photography the TIFF mode is to be avoided, the very slight (if at all detectable) quality loss in a high quality JPEG is by far preferable to TIFF.
When handling the bigger TIFF files in the computer, there is no image degradation when writing and re-writing the file during edit processes. So the best method is to shoot with JPEG files and load those JPEG files to the computer and then when loading an image to edit, make sure you 'Save As' and select the TIFF file type (uncompressed mode if there's a choice). That way further manipulations of the image will not lower the quality. Later when satisfied the image is good and finished with, the file can again be saved as a high quality JPEG to help save storage space.
TIFF is not a wise way to set the camera as the file size and write times disadvantages outweigh any slight image quality advantages. Many cameras do not have the TIFF file choice, and its use in cameras seems to be fading out.
RAW files are mainly only available from digital SLRs and high end compact cameras. The RAW files come with many different proprietary names (like ORF in Olympus and NEF in Nikon etc) but all RAW type files are the real data straight from the digital sensor with no manipulation by the camera's on-board computer. The RAW file can be loaded in the computer and then special software supplied by the camera maker (and increasingly by third party suppliers) can be used to "develop" the image. Applying noise reduction, colour temperature selection, saturation, contrast, sharpness and various other settings that are usually done in the camera and usually altered or selected via the camera menus. The same RAW file can be used over and over with different settings to see if it improves. Usually a better job can be done by the software in the computer than the necessarily short-cut type of software in the camera that is designed for speed more than anything else. Most cameras allow RAW files to be recalled later and processed in the camera itself to produce JPEG files or whatever. That way camera settings and effects can be directly compared to the way the computer software handles the same RAW files.
RAW files have only the original CCD or CMOS sensor data so all the individual pixels are there with their original information. The usual Bayer filter layout on the sensor means that an 8 megapixel sensor will have 4 megapixels of green pixels, 2 megapixels of red pixels and 2 megapixels of blue pixels. And that is what the RAW file contains (plus camera settings data and a small jpeg version of the file for convenience in viewing programs). If you could print a RAW file directly it would look very green due to the abundance of green pixels. So the software in the camera or the computer has to do colour interpolation to sort out a sensible Red/Green/Blue content for every individual pixel even though that same pixel may have started out as containing only Red information (due to its own individual filter) in the camera.
RAW files are smaller than TIFF files so are better to use if there is a choice between RAW and TIFF. Some cameras that produce RAW files can also be made to output RAW + JPEG so the JPEG can be used for quick checking of the image in camera or in portable storage devices and then later the RAW file can be 'developed' in the computer to its full potential. Then again, some cameras produce such good JPEG files that it is mostly unnecessary to use RAW files except for potentially difficult situations.
The big advantage of RAW is that the data from the Analogue to Digital converter either in or attached to the image sensor is accessed, this means you are getting usually more than the 8 bits per colour of data that you get from camera JPEG or TIFF files. The RAW file may variously contain 10 or 12 or maybe 14 bits of data per colour, meaning that this data provides more discrete levels recorded for each colour. Not more colour range but more intermediate levels. While 8 bits of data per colour provides 256 different levels from fully saturated to fully black, 10 bits will provide 1,024 different levels from fully saturated to fully black. That means in the RAW file it is possible when using Curves and other manipulations to obtain more detail in shadow and highlight areas than you would under the same manipulation conditions with an 8 bit file such as the JPEG of the same image.
RAW files can be kept forever for later processing by even more advanced future software or better re-processed when you learn more about RAW file manipulation, thus getting even better results out of the same file.
Summary - RAW is good.
Adobe have recognised that the RAW file situation is a mess and have advocated that companies start using DNG files as RAW type files. DNG stands for Digital NeGative. The name 'negative' is a bit misleading as the image is not negative in any sense, it is just a mess of raw pixel information. If that takes off, all cameras providing RAW type files will output the DNG files type which then will be more easily recognised and decoded by all the participating software. The DNG file with its in-built file information will replace maybe a dozen or more types of RAW files out there that are all mostly incompatible with each other. Adobe supply a free RAW to DNG converter program amongst the downloads on their site. Windows version found at http://www.adobe.com/support/downloads/product.jsp?product=106&platform=Windows the last time I looked. If you decide to convert all your RAW files to DNG, then the original RAW converting software suipplied with your camera may not be able to use them. Programs like Photoshop CS2 and Lightroom will handle them OK of course as that is Adobe software.
When you get to the photo edit program of your choice, you usually find that it can save files in a large variety of ways. If manipulating and adding image layers and correction layers, you will find that the program wants to save the file in its own proprietary format that may not be readable by other programs but does preserve layer and other program specific information for further editing later. If wanting to send the image to a printing lab then it is best to select TIFF or low compression JPEG for that. In doing so all the layers etc in the proprietary files will be 'flattened' or merged to make the TIFF or JPEG file and there's no way that layer information can be retrieved for further manipulation from the TIFF or JPEG unless a copy of the file is kept in that program's own format.
As an example, Photoshop uses xxxxx.psd files, Paint Shop Pro uses xxxxx.psp files and while Paint Shop Pro can read most Photoshop files, you will find Photoshop is not so versatile and will not read Paint Shop Pro files. There's many situations like that, but if you stick to TIFF or JPEG files then there will be minimal problems in sending files to others or using them for printing.
JPEG now has a JPEG2000 version which has better quality lossless compression, but not many programs handle those yet. TIFF also has a lossless compression method, but again, many programs refuse to recognise it.