Digital Image Formats

Digital graphics or images come in two general forms. They are what we call vector and raster graphics. We won’t need to compare or tackle both, as we are concerned with only one of them. Digital photographs are raster images — composed of pixels. But don’t feel relieved just yet. We still have a lot of formats to consider.

First, we have to divide image formats into three types. The first type is the uncompressed format. From what I’ve understood, uncompressed images, such as Microsoft BMP and DIB files, were widely used in the past because they can be processed more quickly, as there are no compressions or encryptions to deal with. This was important because of limited computer processing power. The drawback is that uncompressed image files were very large. We will not be dealing with this group of formats. This leads us to the next two. The next group is what we call lossless and lossy compression formats. Technical data on these two groups abound. But the most important thing we need to remember is that 1) both types decrease file size and 2) lossless compression does not sacrifice image quality as the file size decreases while there is a correlation between image quality and file size in lossy compression.

We will concern ourselves with only a handful of specific formats.

  1. Tagged Image File Format (TIFF) – a widely accepted lossless compression. These two qualities make TIFF an ideal format for storing digital images
  2. JPEG – perhaps the most ubiquitous image file format there is — the MP3 of raster files. JPEG is actually the acronym for its creator (Joint Photographic Experts Group). It is a lossy compression format that allows you to save image files in various compression rates. The downside is that a higher compression rate means losing data, equating to lower image quality. The trick in saving JPEG files, especially if it’s to be published online, is to find that sweet spot – a balance between file size and image quality. Lucky for us, the improvements in the compression algorithms, as well as the increase in available Internet bandwidth has given us the allowance for keeping quality high, without having to worry about file size as much as we used to.
  3. Portable Network Graphics (PNG) – this format had eventually replaced the older proprietary Graphics Interchange Format (GIF). It is now probably the most widely used lossless compression format used in the Internet.
  4. RAW – when you shoot, the camera’s sensor captures a large amount of unprocessed data, much of which is lost and processed when it saves the image in JPEG format. However, some cameras are capable of saving all of that data using what is called the RAW format. This data set may come in useful later on for post processing. I suppose the main drawback here, besides the large file size, is that each digital camera manufacturer (as well as software companies, like Adobe) has its own proprietary RAW format, which change as newer camera models are released. Graphics editing applications, like Photoshop, needs to be updated in order to be able to read RAW files from newer hardware.

Choosing which format to stick with is essentially a matter of how you work with your pictures. For just about all the photographers I’ve known, it boils down to either RAW or JPEG. Most of these people would prefer to use the former. After all, digital storage has progressively become larger and cheaper over the years. Finding a place to store thousands of 12MB files ¬†would have been a costly proposition several years ago. Today, not so much.

On the other hand, there are photographers who beg to differ. They argue that whatever data you need for a digital photo are already there in a typical JPEG file. Using the RAW format is unnecessary for all but a handful of exceptional cases. Sports photographers who need to shoot in high speed have also had to save in JPEG in order to compensate for write speed limitations their hardware may have.

The decision on what to use ultimately rests on you. So, do your research and give a lot of thought about your real needs. A choice will eventually dawn on you.