Intent: this is the first thing to consider when you are taking pictures and choosing the photo file format.
What are you going to be doing with your photograph? Do you plan on sharing them with friends on the web? Do you want to make prints? Do you want to adjust them in an image editing program? In order to make a good decision, you need to know how each photo file format works and what to expect from your image.
JPEG (.jpg) stands for Joint Photographic Experts Group and was developed so that image files could be easily shared on the Internet without worrying about compatibility issues. One standard made things easy and it has become the most widely used photo file format on the web. However, jpeg files are what is called ‘lossy’ meaning they lose information with compression. They also lose information every time they are opened and resaved. This is not a good photo file format if you plan on doing any image editing. They are small files and take up less space on your camera so you can capture more photos on your card than if you were shooting in RAW. A lot more. You can usually choose JPEG quality, too. If you look in your camera manual, it will show you the difference in pixels for all formats and the sizes. Today’s cameras usually show a JPEG print range from about 4×6 for the lower pixel count (and smaller file size) up to 11 x17 and beyond.. Your camera will make colour adjustments to your JPEG file as well as add some sharpening. Also, you will be able to share on the web or print directly from your camera or phone. If you can get more photos on the card, print large photos immediately and share right away, why would anyone want to use RAW?
RAW makes minimal adjustments to the image in camera. The image is exactly as shot and there is a lot more leeway in image editing. In fact, with this photo file format, you must adjust your settings after the image is shot. If you want full control over your photo, this is the photo file format to use. There is no compression and therefore no loss. There is a lot more information in the image so if you are enlarging the photo or want the ultimate quality, shoot in RAW. Be aware that you will have much larger file sizes so fewer photos will fit on your card.
What file format is RAW? It isn’t actually a format. For instance, if you are shooting in RAW on a Sigma, your file extension will be .X3F. Nikon is .NEF. Canon is CRW and CR2. You get the picture. Now this could run into trouble down the road if the company changes the format and no longer recognizes the old one. You would not be able to open your original. To avoid this problem, a universal photo file format was developed for RAW images. It is called DNG which stands for digital negative. There is no information loss and your photo is sure to open no matter what happens to the original camera RAW format file extension. If you use Adobe Lightroom 3 you can convert to DNG when importing.
PNG stands for Portable Network Graphic. It is lossless, which means your file will not deteriorate if you work on it and resave it a number of times. This format handles gradients beautifully and also handles transparent areas in an image, something that JPG cannot do. The files are larger than JPGs so will take longer to load. If you use an older versions of Photoshop (CS3 to CS6), there is a plugin that reduces the size of PNG files and makes them easier to use for the web. Find it here.
Photo file formats in a nutshell:
- Want snapshots of the party you can upload on Facebook right away? Save your space and shoot small JPEGS.
- Want wall art? Shoot RAW.
- Want something in between? If you want to work on it with imaging software, shoot RAW. If you just want some decent prints of your vacation, go higher quality JPEG.
- Need to use transparency? Use PNG.
- Wondering about GIFs? They are not for photography but work just fine on line art and simple graphic shapes with clean edges.
So there you have it. The mystery of photo file formats demystified.