Google Photos Blog - News, Tips and Tricks from the Picasa team

RAW in a nutshell

Tuesday, January 29, 2008 10:43 AM



If you have a higher-end digital camera, you’ve probably seen an option to capture images in RAW format instead of the more-familiar JPG. You might also have noticed that the release notes for recent Picasa releases often refer to “additional RAW support” for new camera models.

So what’s it all about? The RAW image format is a newer alternative to the venerable JPG file format, and offers some technical advantages. If you’re the sort of photographer who’s always looking for the best possible image quality, and often spends time in a photo editor to make your images look absolutely perfect, you may well find that RAW is worth a try.

That said, many photo enthusiasts will argue that JPG already delivers what most photographers need, and that mucking about with RAW is generally not necessary. It’s certainly true that JPG is more convenient, and it has near-universal support – two important considerations.

So which format should you use? It really depends on the user. To help you make a better-informed decision, here’s a three-minute primer on RAW.

RAW vs. cooked

To run with an obvious metaphor, the difference between RAW and JPG is like the difference between an uncooked take-n-bake pizza and a piping-hot pie from the same pizza place. When you order a take-n-bake pizza, you theoretically have more control over the finished product, since you’re the one fiddling with the oven. And should you want to make little adjustments to your pizza beforehand – like redistributing pepperoni slices before cooking – you can do so without making a mess of the cheese and other toppings.

And so it is with camera RAW. A RAW file gives you data from your digital camera’s sensors exactly as it recorded the scene, before the camera ‘cooks’ any post-processing into the image file. This gives you more freedom to adjust and correct the image. With a RAW photo editor, you can change things like white balance, brightness, and contrast without negatively impacting image quality. Once you've adjusted your RAW photo to be pixel-perfect, you'll still need to convert it into a compressed JPG to share it on the web.

A camera-native JPG file, in contrast, is processed by your camera, which decides what the appropriate white balance and color saturation should be, based on your camera settings. The color bit depth is reduced, the picture is compressed, and so on, giving you a picture that’s immediately ready to view and share on the web. Unfortunately, the JPG compression process is fundamentally irreversible, so subsequent changes to things like white balance will have negative effects on image quality. (JPG compression is particularly hard on the blue channel, so if you mess around with white balance too much, you’ll get color or spatial artifacts in your photos.)

Trade-offs

RAW produces the camera’s highest-possible-quality image but delivers it to you in an unprocessed state. This means you have to process it on your computer. Now, presumably you’re going to do a slightly better job than your camera would have done, but hey, it’s still work that a machine could be doing for you.

It’s also worth pointing out that you’ll need the right tools for the job. Although Picasa’s RAW support will do a great job of helping you organize and share RAW-formatted files on your computer, Picasa doesn’t support super-sophisticated editing of RAW files. For this, you’ll need to use either the software that came with your camera, or purchase advanced photo-editing applications, like Aperture or Lightroom.

Additionally, each camera manufacturer has their own version of RAW: Nikon users know it as .NEF (Nikon Electronic-Image Format); Canon users have CR2 (Canon RAW 2); Olympus uses ORF (Olympus RAW Format); while Panasonic just uses RAW. Finally, Adobe has an open standard called DNG. The fact that there’s no single, universal RAW specification makes it harder for photo editors and other applications to support every variant of RAW.

Lastly, don’t forget size and portability. RAW files are much larger than even the highest-quality JPG your camera will produce, taking up more of your camera’s and computer’s storage space. They’re also slower to work with. And if you want to share a RAW file on the web, you’ll have to convert it to JPG first.

My $0.02

When shooting keepsakes and casual snaps, shoot in JPG mode but remember to pay attention to the camera’s white balance setting. You’ll be happy that the files are smaller, look pretty enough to save in an album, and that you didn’t spend hours processing them. If the images are important enough to warrant the post-production time (say, a wedding or a once-in-a-lifetime trip) or if you find yourself in a difficult lighting situation, shoot RAW. You’ll get the best possible quality, and you’ll have a little more freedom when editing. But remember, the advantages of RAW only come into play when you’re willing to sink a little time into processing the images.