RAW versus JPEG

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The pros and cons of RAW versus JPEG file formats

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Introduction - Raw and JPEG defined

what is a RAW file?

When a digital image is captured, light falling upon each photosite (or pixel) of the image sensor is converted to an electrical signal corresponding to the intensity of the light. This signal is amplified and then converted via the camera processor into digital data. The resultant digital file is called RAW.

Most camera manufacturers have their own proprietary RAW file formats. These are generally incompatible with standard image display programmes or printers and therefore require further processing before being widely viewable as photographic images.

What is JPEG?

JPEG processing applies algorithms to the RAW data, which convert and compress the data into the more universally readable JPEG file format.

Certain image attributes are typically also applied during this process, such as white balance, sharpening, contrast and colour rendering and saturation.

When JPEG processing is applied at the highest quality setting (i.e. with minimum compression) there is practically no reduction in image quality despite the reduction in data.

Most budget compact digital cameras and camera phones apply the JPEG conversion “in camera” immediately, effectively overwriting the native RAW file.

More advanced compact cameras and Dslrs typically give the user the following options:-

  1. Convert immediately to JPEG – with predetermined image compression and enhancement settings.
  2. Save only the native RAW file for conversion and enhancement during subsequent post processing.
  3. Save a RAW and JPEG version of the file simultaneously.

RAW versus JPEG pros and cons

So, which format should you use? The following list of pros and cons will help you decide.

  • File size. An uncompressed RAW file is several times larger than a high quality JPEG. e.g. If a JPEG is 5mb, then expect it to be around 20mb in RAW file format. This limits the number of images that a memory card of a given size can store in RAW format compared with JPEG. However, as memory cards increase in capacity and reduce in cost, this is progressively becoming less of an issue. During capture tho' writing the larger RAW files may cause the camera processor buffer to reach capacity sooner – this may limit the number of shots that can be recorded in a single “burst”. This can have important consequences, especially when shooting fast paced sports for example.
  • Flexibility and Image Quality. RAW files contain more data – giving greater control and flexibility when fine tuning image adjustments in post processing. For example there is significantly greater scope to recover details in dark shadows or bright highlights with a RAW file. White balance, sharpening, contrast and colour saturation can also be applied non destructively in post processing rather than at the moment of image capture – where even if test shots are taken, assessment of the results is determined on the small and frequently low resolution l.c.d. Screen of the camera rather than on a larger and higher resolution computer screen which is likely to be in more favourable lighting conditions.
  • Work flow. By preselecting the basic image attributes and having these applied to a JPEG conversion “in camera” - the captured images are essentially ready for display or printing without need for further processing. However this convenience comes at the expense of flexibility and control over the final image appearance.

Which RAW processing software to use?

If your camera allows you to record in RAW format, then the camera will almost certainly be supplied with that manufacturers own proprietary RAW conversion software.

E.g. Canon provides its RAW processing software “Digital Photo Professional” to process its own .CR2 RAW format.

Opinion is divided as to whether better results can be obtained with the manufacturers software or a third party software such as Adobe Camera RAW. It is fact that certain attributes of the RAW file are withheld by camera manufacturers and it is argued that this limits the effectiveness of third party software.

Of course one clear advantage is that the camera manufacturers software is supplied free with the camera, whereas third party software has to be purchased. However, third party software such as Adobe Camera RAW

is included as part of other image editing software that many photographers will purchase in any case such as Adobe Lightroom and Photoshop.

My advice, assuming you have access to both types of software, is to try them both and see for yourself which gives favourable results in terms of image quality and ease of use and control.

archiving your images for perpetuity

A native RAW file is the digital equivalent to a film negative – and provides the most detailed and accurate record of the image as captured.

Furthermore, processing RAW files is non destructive. RAW processing simply attaches a set of instructions (normally in a separate file) that affect how the image is displayed. But the image file data remains unchanged, so it is always possible to revert to the original.

Processing JPEGS however directly affects the image data and once saved – the previous version of the image cannot be recovered. Each subsequent processing of a JPEG file will further compress the file size and thus affect image quality.

For example – if you crop a JPEG, the cropped part of the image is dispensed with – the pixels are effectively “thrown away”. When you crop a RAW file, the cropped portion of the image will be hidden from display, but the data is retained and so it is possible to revisit the image and “undo” the crop at any later time.

For this reason it is generally recommended to always save a RAW version of your important images (remember this decision has to be made PRIOR to image capture – you cannot shoot in JPEG and subsequently convert back to RAW!)

raw versus jpeg summary

RAW gives greater flexibility and control and potentially highest final image quality – but at the “cost” of greater file size and time consuming post processing effort compared to JPEG.

As with many aspects of photography, the ultimate preference boils down to personal choice.

other useful links from Raw versus JPEG

go to JARGON BUSTER digital photography terms explained

Compose Better photos

Ten top tips for taking digital photography

Digital photography exposure explained

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