Although there are hundreds of file formats available for images, most cameras produce either JPG (jpg or jpeg) TIFF (tiff or tif) or RAW. There are advantages & disadvantages to each file type – the choice depends on how you plan to use & store your images.
JPG ( Joint Photographic Experts Group) or JPEG is pronounced JAY-peg, and is the most popular file format for photographic images. JPG images are compressed, that is the file is made smaller when saved. JPG uses what is described as “lossy” compression – what ever information is discarded during the compression process is lost forever. The amount of compression can be determined by the photographer. Most cameras uses a quality description rather than a specific value to determine the amount of compression. Typical might be “Hi” = No Compression, “Fine” = 1:4, “Normal” = 1:8, or “Basic” = 1:16 in the case of the Nikon Coolpix 995, or using numerical values such as 1 – 12 (low to maximum) for Photoshop.
In either case, the more compression you use, the more artifacts show up in the image. The first image is minimally compressed (12 in Photoshop) – it is a 106.5 KB image. The second is the same image saved at the highest amount of compression (1 in Photoshop) – it is a 34.3 KB image. Both are physically the same size (400 X 268 pixels). By the way, the EXIF data is also attached to the images so the actual file sizes are a bit larger…
Notice how blocky the sky has become, and the chunks around the antenna on the van & around the truck. This is what happens when you heavily compress a JPG image. Remember it is lossy – you can never go back to the previous image. Because of this, JPG is a bad way to save your images for the future. It is fine to make the file smaller so you can sent it as an email or post to a web site where you have limited space, but since you have thrown away data, not a good way if you ever plan to use the photo in the future. If you must use JPG (for some cameras it is the only file format available) use the least amount of compression to save your original files. If you use an image editor to save your file as a JPG, be sure to review the image for quality to be sure it meets your needs. It is also a good idea to save the image using”save as” under another name so the original is still available. One last point. Each time you save a JPG the file is compressed. If you open a compressed file, work on it & save it again, you will add more artifacts each time. If possible, always go back to the original file rather than resaving a JPG.
TIFF (Tagged Image File Format) files are quite a bit larger than JPGs, however the advantage is they are either uncompressed, or if compressed, use lossless compression techniques, that is whatever was removed from the file when saved is put back when the file is opened. The TIFF format is often requested by publishers – almost any image editor is capable or reading the format and there will be no compression artifacts generated when saving the file. The disadvantage is the file will be larger. For example, the image above is 353.9 KB when saved as an uncompressed TIFF.
The RAW format is usually available when using high end point & shoot & DSLR cameras. Each manufacturer produces their own RAW format – it is usually not interchangeable between manufacturers or even between camera models made by the same manufacturer. A RAW file contains the data as it comes from the camera sensor. Since some digital cameras produce 12 or 14 bit data files and JPGs are only 8 bit, the RAW file contains more data than a JPG. Using an editor, the photographer can often save an over or under exposed image simply because more information has been recorded.
Another advantage of a RAW file is it has had the least “adjustments” possible made by the camera software. Many photographers compare RAW files to the photographic negative. By itself, it isn’t all that useful, but by using editors that are capable of reading the file, the photographer can often pull more information out of the image than what would be available from a camera processed TIFF or JPG. A typical RAW file will also contain a jpg that is used to preview the image, and data that describes many of the camera settings used when the photo was taken. Editors such as Photoshop, Lightroom, etc use this information to produce the “introductory” image, but using the RAW Converter & tools provided with an editor, the photographer can change any setting.
Some problems with RAW:
- When you purchase a newly released camera, you are dependent on the manufacturer’s editing software until (and even if) 3rd party editors provide updates capable of reading the format. In other words, if you use Photoshop, you may not be able to open files produced by a newly released camera directly in Photoshop for a few months while waiting for an update. Of course, you could open the file in the software provided with the camera by the manufacturer & save it as a lossless TIFF, then open it in Photoshop, but if you want to use Photoshop’s RAW processing capabilities, you will have to wait.
- Since the RAW format is proprietary to the camera manufacture you are depending on the manufacturer and your 3rd party editing software to support the format for as long as you wish to use the RAW files. Adobe (the manufacturer of Photoshop, Photoshop Elements & Lightroom) has a solution – you can convert your images to Photoshop RAW or DNG files. Of course, you are then depending on Adobe to support that format…
- RAW files are useless without an editor. Some will have an embedded JPG file, but it is used as a thumbnail & generally not useful as a final image.
- RAW files are large. Again, taking the example above, the original RAW file is 15.3MB. Of course this is a full size image (3873 X 2592 pixels) since it is directly from the camera sensor, but a same size JPG with minimal compression from the same image would be around 3.8MB. If you take lots of pictures, you will need a large hard disk to save your images.
So why use RAW? Well, as mentioned, it can be considered a negative. Since it may be a 12 or 14 bit file, will likely have a wider dynamic range than an 8 bit JPG or TIFF, and, since most editing software provides more control over an image than the in camera software, will often let the photographer obtain results that would be impossible directly out of the camera. An underexposed RAW image can often be saved where the same JPG turns to mush when attempting to to fix it. If the photographer chose the wrong white balance & saved the image as a JPG, it will be very difficult to fix the balance. If saved as a RAW file, the editor, not the camera sets the white balance, so the problem is easily corrected. My preference is to shoot & save RAW files, however if JPG is all you have available, my suggestion is to save the files at full size & minimal compression, then use an editor to resize both the file & image size to meet your needs, use “save as” for the edited files, and save the original JPG for next time you need the image.