By Ron Ellis
In the digital world, scanning is nearly a thing of the past. In countless prepress departments older high-end scanners sit in the corner and collect dust. Most images are now delivered as digital files. And while these files are ‘ready to go’ and help automate workflows, they often need just as much correction and rework as the files created in the glory days of scanning. There are many different ways to send digital images, and many of them travel as jpg or tiff files. That’s not how most of these files begin their journey from the camera, but that comes later.
From a prepress perspective, a CMYK TIFF file is a usually the preferred way to save image files, however, most images are not created by prepress professionals. Often they are created by professional photographers, or by someone simply using a digital camera to take photos. Most often the result delivered by these cameras is an RGB JPG or TIFF file.
From time to time, however, you may receive a RAW file. For many of us the RAW file format is something mysterious. The camera RAW file format can be dangerous for inexperienced users, but there are times when prepress professionals have a reason to use it. Camera RAW is just what it sounds like — the raw unprocessed data captured by the sensors on the camera. This data is often awkward to use and work with. This RAW file format is custom-created by each camera manufacturer and is different for each one.
For example, the specification for a camera RAW format for a Sony, Kodak, or Fuji camera is different for each of these cameras. The actual RAW data we take pictures with in our consumer cameras is automatically processed by the chip in the camera to give us the resulting photo that we can take and use or print. On a professional camera, they can often process the file automatically or can save the RAW camera data. This raw data has no settings or adjustments, and cannot be opened without some type of software that is capable of opening the RAW file format.
For example, many photographers capture the RAW data and then process it for their customers using processing software such as Capture 1 or Adobe Photoshop. This software doing the conversion must use the proprietary software provided by the camera manufacturer to decode that particular RAW file format.
The raw file format is also data heavy, containing much more information than we typically need to have when we use the image. In the raw file format, the white point and other aim points have not yet been decided, so the image may be quite hideous looking when opened.
Many professionals refer to the RAW file format as the digital negative, because like a traditional negative you can use this file to improve the quality of the image.
What type of improvements can be made using the RAW file format? To start with, the RAW file format usually contains greater bit depth than that of finished images. The RAW image has not been adjusted yet, so the original unadjusted data is there and can be viewed in the histogram — and often the quality of the shot can be ascertained by looking at the quality of the histogram.
When processing the RAW file, the photographer will choose the settings that decide the exposure, aimpoints, and other settings that will decide the quality of the image. Even a good image may look poor in the raw format before processing, so this step is very important.
Among the benefits of the raw format is the fact that it has been altered, it hasn’t been compressed, sharpened or changed like many processed formats such as JPG. Data hasn’t been thrown out or lost yet, and no bad color correction decisions have yet been made. In the hands of a talented photographer or professional retoucher, the processing step can be used to make good images look even better. The computer and software that the photographer uses to perform processing has much more power and control than the embedded chip on the computer that is typically performing this conversion.
Additionally once a file is converted, the original raw data is lost forever. If the raw file is saved and archived, then the file can be reprocessed with different settings, allowing a significant amount of control and the ability to modify the settings of this ‘digital negative.’
White balance and aim points can be set on the raw file. Raw files also are 12 bit files, which means they have much more data being used for tonal definition than the average 8 bit JPG or tiff file. (Typically these defects appear as posterization.) This means there is much more data available for correction and processing before the final alteration.
All this power comes with danger as well. For the average digital artist, choosing the right setting is difficult. It is easy to fix the image too much, and blow out one or another part of the image.
Typically, the photographer processes the file, and this is usually the right person for the task because the photographer was at the shoot and knows that they intended the image to look like.
What file format should we as printers request from agencies and photographers when we work with them? Typically we would like to have an RGB or CMYK tiff file (RGB if we want to do the separation, CMYK if we trust them to do it) — and also the RAW file. Most high-end separators and printers will use the tiff file to make the first proof, and if there are problems will then go back and reprocess the raw file to get the desired effect.
The intent is always to use the TIFF, but if there is a problem it is nice to have the RAW to go back to.
About the author: Ron Ellis is a prepress consultant specializing in workflow training and integration. He has consulted on numerous CTP installations and he provides color management, integration, training, workflow development, and troubleshooting solutions to the graphic arts community. He can be contacted at 603-498-4553 or through his web site at www.ronellisconsulting.com.