Raw
What are RAW format images?
RAW is a native camera image format that records the light exactly as recorded by the camera's sensor. It is different from JPEG in the following respects:
- RAW is the "raw" data from the CCD - quite often in RGBG format, whilst JPEG is "processed" into a viewable image.
- RAW data is uncompressed so the full resolution of the original image is preserved. JPEG images are compressed to save storage space, so the full resolution of the original image is lost.
- Many camera CCDs record more than 8 bits of information per pixel and colour. 12 bit sensors are common and RAW files contain this info. JPEG files use 8 bit RGB values so information is lost here too.
You can think of RAW images as similar to unprocessed film - you can still process it any way you like. JPEG is like processed film (negatives or prints), the processing has already been applied and any further processing will produce a lower quality end result.
There is no single RAW format; every manufacturer has their own version. Photo processing software usually can read RAW files from different cameras, though it may not honour all settings or be correctly calibrated for that camera. e.g. Adobe Camera Raw software requires custom calibration for each camera.
Recently, ADOBE have introduced the DNG or Digital Negative file format. This is a standardised RAW file format that many camera manufacturers are supporting that can be imported into PhotoShop without further calibration. Some cameras allow RAW files to be saved in DNG or the manufacturer specific format.
In short, you use RAW because it allows you to get the best image out of each frame you shoot. But that power also requires extra effort to get them looking their best.
Shooting in RAW
When you shoot in RAW the image saved to the camera's memory card is exactly what its sensor recorded. This is important to know because it is not the same as the image you see on the preview LCD at the back of the camera. The image you see on the back LCD is basically what you would get if you shot in JPEG instead; it applies in-camera settings to "process" the image into a viewable format, as described in the introduction.
In-camera settings are things such as White Balance, contrast, saturation, etc. When you shoot in JPEG these settings are used to define the saved image's appearance. When you shoot in RAW these settings are saved along with the sensor image data, but they are not used to define the saved image. The camera uses them to display the preview, but they don't "destroy" the basic light information. In RAW you can change these settings later in your editing software if you want.
Disadvantages of RAW
RAW files take up a lot of space on memory cards - typically about 10 times the space of a JPEG file. Also, images for inclusion on VW will almost always be submitted in JPEG format. If you do not want to do extensive image processing after taking the photos, then RAW files are probably a hassle. You'll also need a newer computer and faster processors to convert huge RAW files. Having the latest DSLR with a ten year old computer might not work as great as you think. You may need to let your old computer run batch processing overnight to convert the images on your card.
Commercial Photographs
If you expect your photos will be sold for publication in books, then RAW files will be required. As a rough guide, most commercial images are expected to be uncompressed (so no JPEG) of at least 8 megapixel resolution - this is sufficient to print an A4 sized image at 300 dots-per-inch. Many magazines simply raise this limit as DSLRs keep getting more and more resolution to limit the suppliers to those willing to purchase the best cameras available at the moment. For many commercial uses, if your camera supports it, also use Adobe rather than sRGB color-space, but be careful here as some do and some do not. Know your customer's requirements.
Importing RAW files
The software that came with your camera is able to import RAW images. When you view the images on your PC the software takes the in-camera settings saved with the sensor data and uses them to process the image, exactly the same way as the back LCD preview on the camera itself. When you export images from such software it also uses the in-camera settings to process the exported image too.
Other image processing software can also import RAW files. In Photoshop you need the plug-in module Adobe Camera Raw; in Lightroom this is embedded already. The difference with third party software (like these) and software that came with your camera is that the camera's bundled software applies a built-in settings profile while third party software lets you choose your own.
A settings profile is the same as in-camera settings, except that you record it on your computer instead of your camera, and it is more flexible and precise.
Because camera bundled software already has a settings profile set within it, importing RAW files is easy and the images appear exactly the same as they did on the LCD panel. The software also reads the in-camera settings and adds those settings to its own to process the image. This simplicity means that first time import is easy, but it is really hard to change afterwards.
Third party software uses a settings profile that you set up initially. First timers often report that when they import RAW images that they appear dull and lifeless; this is because the default settings are not calibrated for the camera. After you adjust these settings the imported RAW files can look far more vibrant than the preloaded settings used by the camera software. It takes considerable effort to set up and maintain these settings. But you use them because they allow you to process the RAW file to a greater degree of accuracy and vibrance than you ever could using in-camera settings alone.
Editing in RAW
Some software (e.g. Lightroom) allows you to adjust the settings profile of an image even after import. This means you can fine-tune each image to capture the best white balance, saturation, contrast, etc. RAW editing is really just an extension of RAW importing.
After editing, saving to a format that is lossless is recommended (e.g. PSD, TIF). Saving to RAW is unlikely unless provided by the camera manufacturer. Save as... a JPEG to a second file if edits are complete.
