There are many formats that photos can be stored in. Some are designed to preserves all the available information and others are designed to make files smaller while retaining most of the information. Most cameras are set to save the photos as JPEG files, which is a very common format that is designed to make files smaller by compressing the data, sometimes making the file 10% the size of the original. This is important when you are storing a large number of photos on a computer, emailing the photos, or posting them on facebook or other photo sharing sites. However, this compression comes at a price. Some of the information captured by your digital camera has been thrown away when saved as JPEG format. Also, when you take the photo in JPEG format, the camera applies some automatic edits before saving the file, including exposure, color, contrast, saturation and sharpening. You can't easily undo these automatic edits if the file is saved in JPEG.
The alternative is to use a lossless format which keeps all the original information captured by the camera sensor. Raw files are just that - raw unprocessed image files directly from the camera sensor. None of the information has been lost and no processing has been applied to the file. It is in it's original "raw" state.
The downside of raw files is they can be very large. The ones that come out of my Canon 5D Mark ii are about 24 megabytes. They can fill up a memory card pretty quickly and take a long time to download to a PC. These raw files cannot be displayed or edited without some special software with raw converters, such as Adobe Lightroom or Photoshop.
On a recent hiking trip I overheard a group of photographers in the Raw vs. JPEG debate. One made the statement that you really don't get much benefit from using the Raw format and JPEG was just as good. I just went about my business shooting the scenery in Raw format without jumping in and telling them they really weren't right. The best way to illustrate my point is by example.
Here's an unprocessed raw file from our trip to Korea.
|Unprocessed Raw File|
This is what you typically see when there is too much contrast in the photo. The sky is "blown out" where you can't see any detail. The structure on top of the wall is dark where you can't see details in the shadows. The information in these areas is still there in the raw file and can be pulled out in a photo editor that supports raw format.
|Raw file after editing|
Here's the end result after editing the raw file. You can see the clouds in the sky and the details in the structure that didn't appear to be there. If I had taken the photo in JPEG format much of this information would have been discarded in the compression process. I didn't take a JPEF format of this photo, but I can simulate it by converting the raw file into JPEG format.
In the photo below I started with a JPEG file and applied the same changes that I did to the raw file to see if there is really a difference.
|JPEG after editing|
This is just one example. The more extreme the shooting conditions the more valuable the raw format becomes.
Not all cameras support raw format. All DSLRs and some mid-range compacts do. If you decide to try raw format, then remember you will need a software package to read and process the files.
More photos from our trip to Korea are available online in the Travel Gallery