What is Camera RAW Files

raw files

Both Digital Single Lens Reflex (DSLR) and some digital point-and-shoot cameras provide users with the option of shooting in either a jpg or RAW file. A jpg is a standard and universal format for digital images;

RAW files are not as standard and universal. Many professional photographers shoot in RAW. So, what is a RAW file, why do professionals use it, and why should people consider shooting in RAW?

What are RAW Files

RAW files are images that have not yet been processed and are not printable without further tinkering. A RAW file must be imported from the cameras memory card to photo processing software.

Each camera manufacturer has image processing software that can convert the RAW file to a jpg or TIFF. Adobe also offers a variety of popular products for processing and editing images that work with RAW files; Photoshop and Lightroom are two.

One issue with RAW files is that, each camera manufacturer has its own RAW file format. This requires either obtaining their specific, proprietary software in order to process the images or locating third-party software that is compatible.

For example, Photoshop will usually need to have updates installed so as to be able to view RAW files from a camera manufactures latest camera.

How RAW Files Work

The colour or brightness data from each pixel is saved onto the memory card. No data is lost but fewer images fit onto the card, and each shot takes longer to save.

For instance, a Canon G9 takes 4000 x 3000 pixel images. With a 4Gb card it takes 1250 high quality JPGs, but only 190 images saved as RAW files.

The advantage of the RAW format is that when it is opened on a computer, the photographer can make changes to the settings for exposure, white balance and saturation, which would not be possible on a JPG without downgrading the image quality. Software may allow more complex adjustments, like correcting barrel or pincushion distortion from the lens, or selectively lightening the darker areas of an image.

Why Shoot in RAW?

The advantage to using a RAW file is it contains more information and has a higher range of digital information than what a jpg would contain. If the scene is to dark, with a RAW file it will be possible to obtain more detail out of the shadows. If the scene is to light, it will be easier to process the image and bring out detail, if it is available.

The best way to think of RAW files is as a film negative. The negative holds all the image details. It can’t be used to view the image directly but the negative is used to create the final print.

The final print can be thought of as the jpg. If making copies of that print, it would be better to use the negative over the final print; the same relationship exists between RAW files and jpgs.

RAW Means More Computer Time

JPGS are a universal format and can be downloaded straight to a printer, viewed on a computer, emailed to friends or posted on websites. RAW files are more labour intensive.

RAW files can’t be used for printing straight off the camera. They have to be downloaded onto a computer. It reads the pixel data and displays the image. Different camera makers have slightly different way of encoding the pixel data. It has to be read with their software, usually supplied with the camera. Image processing programs like Adobe Photoshop can have a plug-in from the camera manufacturer to read the raw file.

Once the image is corrected, it can be saved as a TIFF which is a standard format that preserves the pixel data. It can be corrected again without problems if it is saved as a TIFF. Or, to save disc space, it can be saved as a high quality JPG if no more correction is needed.

Disadvantages of Shooting RAW

As motioned, each camera manufacturer has its own version of RAW for each camera. It can be true, however, that this can vary from similar cameras within the manufactures line. For example, when Canon launched the 5D Mark 2, third-party manufactures had to do updates even though they were compatible with the first version of the 5D.

As technology evolves, it is possible that later versions of software won’t be compatible at all with older cameras’ RAW files. Users might have RAW files that they will eventually be unable to process.

Just like people who still have musical 8-tracks can’t find stereos with 8-track players anymore, people may one day be hard pressed to find compatible RAW processing programs. Adobe is attempting to offer an archival file format known as Digital Negative (DNG) in order to solve this possible problem.

File size can be another issue for RAW images. Since each RAW image holds so much information, the file size is much larger than it would be if it were a jpg and cameras takes a few macro seconds longer to process it with each click.

Photographers need to have larger memory cards and more space on computers for the files. On top of that, since the image has to be converted to a jpg for printing, users have to store and track two files of the same image, the RAW file and the jpg.

When shooting large scenes such as nature or scenes with a high contrast between the darks and the lights, shooting in RAW will provide a photographer with more options and control in the development of the final print, making the additional file size and processing time worthwhile.

Yet, if shooting just friends and family during the weekend barbeque, where the lighting is well set and the images will most likely just get loaded to a website for printing in 4×6, shooting in RAW might be more than is necessary.

RAW Image Files Compared to JPEGs

green grass near the gray road

The Pros and Cons of Two File Types in Digital Photography

Most digital photographs are recorded, stored, manipulated and shared as JPEG files, easily recognized by file names ending with .jpg and named for the Joint Photographic Experts Group that designed their format in the early 1990s. JPEG (pronounced jay-peg) files have become almost universally accepted.

JPEGs are fine for most purposes. They usually give a pretty good visual image; their relatively small size makes them easy to store and share; and their near-universal acceptance makes them easy to distribute and access.

How JPG s Work

The data from the camera sensor is processed by a mathematical formula devised by the Joint Photographic Experts Group. The sensor contains 10, 12 or more million pixels, each sending a numerical message to record either brightness or red, blue or green colour. That’s a lot of data. Compression reduces the amount of data. An outline idea of the process:

  • information that is less important to the human eye is discarded
  • the data is grouped in 8 by 8 pixel areas
  • colour and brightness are recorded for these pixel areas

The result is a much smaller file size. As well as doing JPG compression, the camera applies settings like white balance, saturation and sharpening. These can be set by the user. For instance, if shooting under incandescent light, choosing the correct white balance setting produces natural pictures without a yellow colour cast. Shooting flowers or landscape, the user can increase saturation for a more vivid effect.

A disadvantage is that if the photographer wants to make further corrections on a computer, the image gets degraded every time it is opened, altered, and re-compressed. Square marks due to the pixel grouping can appear.

Benefits of JPEG Image Files

The main advantage of this format are that it not only saves you lots of storage space on your camera’s memory card as well as your computer’s hard drive, but it is also very compatible with nearly any image viewer that can be found. Of course, there are trade-offs for the photo-enthusiast interested in using this format.

The Limitations of JPEG Files

But JPEGs have two important limitations. First, from the moment they are created in the camera they contain only some of the information that most camera sensors are capable of recording. Camera manufacturers often include various program modes that give the photographer some control over which information is kept and which discarded, but that control is quite crude and not much can be done once the conversion to the jpeg format is made.

The JPEG file’s second limitation is its “lossy” method of data compression, meaning that the information the file contains is compressed in such a way that some data are lost, and more may be lost each time the file is edited and re-saved. Users can control how much is lost by setting high or low compression levels and by saving or stripping out some of the file’s “metadata” that summarises things like the date and camera settings when the shot was taken.

What JPEG Loses in the Translation from the Image Sensor

The biggest trade-off is that the compression scheme throws out lots of bits of information in order to get the image’s file size smaller. Now, throwing out bits isn’t necessarily bad, but the algorithms used by the JPEG format do this in such a way that the information it tosses is truly lost and unrecoverable.

In general, for the web, 4×6, or sometimes even 8×10 prints of properly exposed pictures, the in-camera JPEG images should be fine. But the loss of data becomes really apparent if you reopen the same image many times for editing and re-save it, or if you try make a really large print from an image that has a high compression ratio.

How a JPEG Image is Different from a RAW Image

An in-camera JPEG image file is data from the camera’s sensor that has been processed by the camera, and is nearly analogous to being a printed image. Like a photographic print, this image file is more limited in the capabilities for improvement.

On the other hand, a RAW image file is typically data straight from the camera’s sensor, or possibly with minimal processing of that data, and is more like a photo negative which needs to be developed prior to making a print. Thus the RAW image file will be much larger.

Now, while RAW image files are much larger and take a bit more time to write out to the memory card, they provide nearly all of the information available to the camera from the digital sensor. Having all of this information in your image file gives many capabilities that aren’t available from a JPEG image file.

What You Can Do with a RAW Image that You Cannot Do with a JPEG Image

For example, if the white-balance is not quite right in the image, for example if it has a red or blue cast to it, a RAW file provides the ability to change the filtering on the interpretation of the data to mask out the color cast from the ambient lighting.

While this can be done to some extent with a JPEG image, the flexibility in the RAW image gives much more power to fix the color casting in a picture. You can easily make a picture with a really red cast from incandescent light bulbs into one which looks quite natural.

Advantages of RAW over JPEG

However compared to JPEGs, the great advantage of working with RAW files is that photographers have far greater creative control over the process of converting the data recorded by the sensor into a readable format; in other words, in deciding which information from the sensor is to be kept and which discarded when constructing the final RGB file.

As a very rough analogy, RAW files may be compared to JPEGs in the same way as traditional film negatives may be compared to transparencies.

Why use RAW files like NEF, CR2 Instead of JPG?

Point-and-shoot compact cameras usually save images in JPG files. (also called JPEG). Digital single lens reflex cameras and high-end compact cameras can also save images as RAW files. Canon, Nikon, Sony, Sigma, Panasonic, Olympus and Pentax all make cameras that can save RAW files. The RAW files have different file suffixes like CR2, NEF, X3F depending on the camera manufacturer.

The difference between JPG and RAW is that the JPG is compressed to save space on the memory card, but the RAW file holds all the information from the sensor. Compare how the two formats work to decide which is better to use:

The Trade-off between Quality, Time and Hard Disc Space

The photographer using RAW files has greater creative control to optimize images. Retouching to remove litter from a landscape or lines from a face is better starting from RAW. Less experienced photographers may appreciate the ability to correct exposure and white balance after the event.

Professional photographers may save time and hard disc space by shooting high quality JPG. Wedding photographers often use JPG as they are working in a controlled environment where lighting and white balance are predictable. They gain faster workflow and less hardware costs

Fixing More than Just White Balance

There is also much more flexibility in correcting exposure when developing the RAW image than after it is in JPEG format. You usually have a lattitude of up to three “stops” of exposure with RAW image files – this is a much greater lattitude than is available in a standard JPEG image.

For example, if the JPEG image has clipped highlights or shadows, that data is forever lost. However when processing a RAW image file it is usually possible to recover details in those highlights and shadows to add more depth to an image.

This can be very important for images with a large range between highlights and shadows, allowing the details in both to be provided in the final image.

RAW Advantages Outweigh the Disadvantages

Even though processing RAW image files takes additional storage capacity, as well as process steps and time in working with pictures, the overall benefits of the final output can often be well worth the effort.

The choice of whether to shoot pictures in RAW or JPEG is determined on how much effort post-shoot one wants to put into the pictures.

And while initial forays into processing RAW image files may be a little confusing and daunting, becoming comfortable with processing RAW image files can open up many new options, also save pictures which otherwise would have been lost.

Choosing a compact camera or DSLR

The latest digital compacts take great pictures, even in economy price brackets. Camera choice depends on how it is to be used. For instant printing without involving a computer, or for display in a digital photo frame, or posting on a website, a camera that just shoots JPG files will fit the bill.

On the other hand, cameras that have the option to shoot RAW or JPG are becoming increasingly affordable. Then the photographer can set the camera to RAW for maximum creative control, or JPG for speed and convenience.

RAW Image Processing Software

Typically, RAW processing software has precise controls for the white balance, hue and saturation, and even the exposure can be adjusted during post-processing. While it is true that programs like Photoshop have similar controls that can be applied to JPEG files, the wider range of values for each pixel stored in the RAW file allows for greater and more accurate adjustments without risking the appearance of posterization and other unnatural effects.

Having a wider range of values available allows for more subtle colour gradations, and is especially useful in areas of highlights and shadows, where a great deal of detail can often be recovered within a RAW file that would have been lost in a JPEG image. This in itself is enough to persuade many photographers to adopt a RAW workflow.

Until a few years ago the availability and accessibility of software was a constraint on working with RAW files, but not any more. In 2008 Apple’s Aperture and Adobe’s Lightroom are probably the leaders in the field, but other good choices are available and worth a look.