Understanding JPG & RAW File Formats

Whether you are familiar with digital SLR photography or not, you are very likely familiar with a JPEG or JPG. Most of the digital photos you have seen have likely been in the JPG format and as such it is quite a popular format for digital photos. But in digital SLR photography, there is an additional file format most often referred to as RAW.

In the world of digital SLR photography there is always the debate regarding which image format is better, JPEG or RAW. The fact is that neither is “better”. It comes down to a personal preference. Its important to understand what each format is since every digital SLR camera gives you the option of whether you wish your images captured in JPEG, in RAW or in both formats. So, how do you make that choice. Let’s first look at the JPEG format.

Sixty four BILLION color  tones!

Most digital cameras have the ability to record images using a range of over 64 billion different colors or tones. This is a combination of 4,000 different tones of Red, 4,000 different tones of Green and 4,000 different tones of Blue. Thus the term “RGB”. When you take a photo, the digital SLR will originally record the image using these 64 billion different possible tones. If the DSLR is set to record in JPG format, the camera will then convert the image and in the conversion will “only” use 16.8 million possible colors – 256 different tones of Red, 256 different tones of Green and 256 different tones of Blue. Once it reduces the range of colors it then compresses the image.

Basically, the JPG format is a compressed format and is commonly referred to as a “lossy” format because image information is being discarded in the process of compression. What happens during the compression process is that through a complex algorithm, a pixel by pixel comparison is made and similar or redundant pixels are discarded.  The interesting and most important aspect of the JPG format is that every time you open the image, make a change to it, then save it, the compression process begins again. Therefore over time the image losses more and more “information” each time it is saved and therefore degradation takes place.

All digital SLR cameras give you the ability to decided how much compression you would like. The more compression you choose, the smaller the image file will be and therefore the more images you can store on the camera’s storage device. Unfortunately there is no standard compression ratio among manufacturers with each having their own discrete steps of compression.

And then there was RAW!

So how does RAW differ from JPEG? Firstly, RAW is not really a format. More specifically it is a broad term applied to proprietary formats created for each individual digital SLR manufacturer. Each manufacturer’s RAW formatted image will have a specific file extension for that manufacturer.

Put simply,

RAW is the original uncompressed image that still retains its full range of tones and colors (64 billion different possible tones), without any pixels discarded.

The most important aspect of this RAW format is that it allows you, after the image has been taken (this is the cool part!), to change those settings that you originally made in the camera: white balance and exposure (to an extent), including sharpness, contrast and color saturation. Once you make those changes, you simply save the image in a JPG (or other format) and retain the original RAW image for another day!

Can you tell the difference?

So, which is better – JPG or RAW?  Here’s a test:

Image A

Image B

I shot the subject to the right in order to give color, texture, depth and contrast.  One image was shot in-camera as a JPG and the other image was shot in-camera as a RAW file then saved as a JPG with the same pixel dimensions and resolution. Can you determine which image is the original JPG and which is the original RAW? …. It’s not easy, is it!  Image A is the original JPG and image B is the original RAW.

There are a number of factors that go into choosing which format to shoot in, but don’t necessarily make “quality” the over-riding factor.  Ultimately it comes down to how much post-processing you wish to do since shooting in RAW involves using the camera’s software to open and process the RAW image into a usable format. The great thing about digital SLR cameras though is that you not only have the option to shoot in JPG or RAW, but you can also choose to shoot in BOTH at the same time.

If you wish to learn more about the advantages and disadvantages of shooting in either JPG or RAW read ……

The next article in this series is “Introduction to White Balance”

If are looking to start exploring digital SLR cameras, jump to the “Choosing a DSLR Camera” section.

Otherwise go back to Getting Started in Digital SLR Photography.

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