Advanced Tutorial 7

Advanced digital cameras can be set to create images files, stored to a memory card, in the universally shareable JPEG format, or as a RAW file. So, what is the difference between the two and what advantages are offered by opting for RAW files and then post-processing your images on a computer?


Shooting in RAW or JPEG?

The majority of digital cameras automatically save still images using the JPEG file format, as this is an easy format to handle and universally compatible with many display devices. However, as it is a ‘compression’ format, there is sometimes a requirement or desire to work with the original, uncompressed raw data.

Much is talked about the benefits of shooting RAW rather than JPEG, but there are positives for both formats – so which should be your preferred shooting option?

What is RAW?

Put simply, RAW is the file format used by modern digital cameras to retrieve the data from each pixel of their image sensor. The data is held in a format of binary code that has yet to go through any of the camera’s image processing, hence it is called ‘raw’ data. At this stage, the data cannot be viewed on the camera’s screen; it can only be viewed on a computer by loading the file into a software package called a ‘RAW developer’. The software converts the binary zeros and ones into Red, Green and Blue values, for each pixel location, allowing the coloured image to be displayed.

Being able to see, immediately, images that you have just shot is pretty fundamental to digital photography however, so even if you set ‘RAW only’ as your shooting format, the camera will still create a JPEG thumbnail image for viewing on its screen. Most cameras offer a ‘RAW and JPEG’ shooting option, meaning the RAW file and a full-blown JPEG are both saved to the memory card.

Compression Quality Menu

Compression Quality Menu

Compression Quality RAW & JPEG selected

Compression Quality RAW & JPEG selected

The creation of RAW and JPEG images

Creating a JPEG file involves applying a number of processes in order to conform to the format’s specifications, requiring complex logarithmic calculations and much processing power. There is no doubt that the huge processor resources of a home computer greatly outweigh those contained in the camera itself, so it follows that when a camera creates a JPEG it will not be as accurate a representation of the original subject as a computer can achieve.

Processes such as ‘demosaicing’, ‘gamma correction’, colour saturation and sharpening are all applied according to your camera’s spec; finally, ‘Dynamic Range’ is clipped in order to create the 8-bit (256 levels) depth limit of the JPEG format.

RAW processing on a computer allows all of this to be managed by the RAW developer software and allows you to fine-tune further parameters, including exposure, white balance and noise reduction. Once you are happy with your corrections, a new image can then be saved as a JPEG – or any other image file format you select.

Any corrections made via the software are stored as control values and do not change the original data. Therefore, no matter how many changes you make, how many new images / files you create, the original data remains intact.

Any ‘lossy’ compression method involves data loss – compromising the original data, in order to create a smaller file size. It is inevitable that some original data will be discarded and, once a compressed file has been created, it is not possible to retrieve it. An area where this is most noticeable when comparing RAW and JPEG files is in the Dynamic Range (DR).

The native DR of high-end cameras is always greater than the 8-bit used by JPEGs. When DR is limited, so is the ability to capture details in brightly lit or shadowed areas. RAW images maintain the native DR, offering the ability to retrieve details that may be otherwise lost in dark areas due to underexposure, or vice versa for overexposed areas.

Compare these images below to see the improvements made after developing a new JPEG from a RAW file.

(The images have been slightly cropped from the original):

JPEG Original(crop)

JPEG as captured in camera (Cropped)

JPEG from RAW(D)

RAW converted to JPEG after software correction (White Balance, Exposure Bias & Perspective shift)

The drawbacks of RAW shooting

So with the superior image control that RAW shooting offers, why is it not used all the time?

Here are some of the disadvantages that need to be considered:

  • RAW files are much larger than JPEG files – three or four times as much data. Although storage is getting cheaper, file transfer speeds could also be an issue.
  • Your camera and memory card-processing speed will limit burst shooting rates. Because of the larger file size of RAW, your camera will significantly slow down while the image is captured.
  • RAW files require a lot of manual input to post-process on a computer. Some skills may be required that go beyond regular JPEG manipulation.
  • RAW files cannot easily be shared, as specific developing software is required to view them.
  • RAW files are unique to each camera model, therefore new software or plug-ins have to be developed for each model that is released. It may be a while before your preferred photo manipulation software package supports a new camera model.

How to view or edit the files

All camera manufacturers supply RAW developer software with their cameras, in order that the images can be viewed on a computer immediately.

Most of the time, the supplied free software is pretty basic – it may not offer all the editing features normally found in the more sophisticated packages.

The large software developers normally release plug-ins for their popular photo-editing packages offering RAW development support for new camera models within a few months of their release.

Whichever development software you choose to use, the RAW image needs to be ‘developed’ into a useable file. This generally means the image is saved as either a compressed JPEG or in the uncompressed TIFF file format.

The LUMIX Advantage

LUMIX G cameras come supplied with a sophisticated ‘non-destructive’ RAW development software package, called SILKYPIX Developer. Non-destructive means that no matter how many times you apply corrections to the RAW file, the change process is saved to another file and the original RAW data is preserved. Here is just a small sample of the image control parameters that SILKYPIX offers: Tone Curve, Colour Saturation, Colour Picking Tool, White Balance, Contrast, Exposure Bias, Sharpness / Noise Reduction, Lens Aberration Correction, Rotation and Digital Perspective Shift, Trimming and Printing.

Such additional complication may be off-putting, but time spent post-processing will reward you with the exact results you seek in your photography. Images can be developed separately or as a batch, and developed files can be saved as a JPEG or TIFF. The other advantage of using the manufacturer’s supplied RAW developer is that the conversion logarithms are optimised for the manufacturer’s own camera and lens software.

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Written by Steve Lucas for Panasonic ©