JPEG vs RAW, and why Pixii is a DNG-first camera
Short version : RAW is a digital file format developed for maximum-quality image processing, while the JPEG image format is optimized for display. Now let’s dig deeper to explain the important differences and our technical choices.
In the left corner, JPEG
In 1986, most Pixii users were still children, and computers couldn’t display graphics or pictures. Only text. The Joint Photographic Experts Group (JPEG) was the first to propose an image format that was compressed enough to be displayed using the limited hardware available at the time. Many have followed, but this first-mover advantage has made the clever image format largely universal today.
At the core of JPEG is the concept of compressing the file as much as possible without introducing too many visible artifacts. The level of compression can be set by software, allowing to optimize the quality/size compromise for every specific application.
In the right corner, RAW
A RAW file is comparable to the latent image present on a film before it has been developed. It cannot be displayed on a computer - your editing software creates an image that can, from the RAW file, you are not viewing the RAW file itself - and is only used for post-processing.
Uncompressed (or losslessly compressed, in some cases) and unprocessed, the RAW file contains a digital rendition of what the sensor captured. It is a digital file, but not an image. RAW files must be imported to editing software, which allows them to be processed and exported to an image format that can be displayed or printed.
Pros and Cons of both formats
Here is a series of criteria that can allow you to choose the best format for you, and the respective strengths and weaknesses of both.
Image quality
RAW: The best possible image quality is always obtained in RAW files.
JPEG: Image quality can be very good if the image requires no further editing and compression is kept reasonable.
It makes little sense in practice to buy “the best” camera, “the best” lenses and shoot in JPEG. RAW files can have a bit depth of 12 bits or more, where the JPEG format limits it to 8 bits per channel. The color space used by JPEG allows 16.8 millions distinct colors to be displayed, which is excellent for display, but nowhere near enough to edit. In practice, RAW color spaces such as Adobe RGB and ProPhoto RGB offer a far wider gamut.
Dynamic range is also much more restricted in JPEG than in RAW (typically 11 stops, compared to 13 or more), so shadows are more easily buried and highlights more easily clipped. And when that clipping occurs, it is typically more brutal and ugly because of the lower amount of data present in the file. Sunny blue skies can be very tricky, often impossible, to reproduce correctly in a JPEG image, for example.
The original JPEG photo is a bit under exposed.
But even with a slight adjustment of exposure or white balance, JPEG starts to show its limits.
The histogram of the 2nd, edited version, shows a comb effect indicating that the file is beginning to break up.
Artifacts
RAW: In theory, uncompressed files introduce no artifacts. If such artifacts as moire are present in the image collected from the sensor, they will be transferred to the file, but not be created by the format.
JPEG compression is not well suited to sharp contrasts between adjacent pixels. So photos of printed text or geometric patterns will contain many visible and unwanted signs of the compression. In practice, this is often dealt with correctly, but the artifacts are still there and visible to critical observers.
Other artifacts are present in the JPEG format, too. You can find a complete description of them here. You can find software that will help with removing them. But if you’re going to start editing, why not use the far superior RAW format?
Colors in a RAW file captured with the original Pixii Camera.
Size (compression)
RAW: True RAW files are uncompressed or losslessly compressed. Anything else uses the name RAW, but is not really RAW. So, true RAW files are big (typically 20-200Mb each).
JPEG compression can be user set in editing software, either by selecting the compression factor itself or by setting a ‘quality’ parameter. But the stated average is typically a factor of 10, meaning that JPEG files are usually about 10 times smaller than the RAW files they were exported from.
Even with high-speed Internet, the web needs photographs to be as small as possible. Cloud storage is expensive, Google SEO shuns slow pages, as do users. So, even if RAW files could be displayed, JPEG would win this round every time.
JPEG also makes sense in some cameras for faster continuous shooting. Or for a smaller backup device.
This - heavily lossy - JPEG compression, however, is what makes the JPEG image unsuitable for post-processing. Even something as simple as a strong White Balance adjustment can introduce unwanted issues, but it’s the succession of edit steps that will always seriously degrade the image (through a phenomenon akin to digital generation loss).
Convenience
RAW: Most manufacturers tend to create their own proprietary format, which is a shame. Only DNG is an open format that can be used on almost every editing software. This is why Pixii has elected to use DNG.
JPEG: While the ‘pure’ version of JPEG is not that easy to use, variants have emerged and all are compatible with virtually any image display, browser, social media or device you can imagine.
Again, note that JPEG images are more convenient, if you are going to use them as they are. Sharpness is set in camera and near impossible to alter. White balance also is set in camera. A RAW file has no set white balance setting (the file has a wb field "AsShotNeutral" typically). It is only displayed as the camera was set in editing software by default, but can be changed after the fact. Not so easily with a JPEG image. So JPEGs do not allow for mistakes or any desire to add your own touch in post processing.
Note that when you take a picture in JPEG format, the camera automatically applies adjustments to it and acts as a black box when doing so. Presets aside, you have no say in the matter, which feels like a shame in a creative pursuit such as photography.
JPEG images are more convenient, RAW files are more flexible. Plus, you can generate a JPEG from a RAW, but not the other way around.
An analogy with film photography
When a film has been exposed to light, a chemical reaction starts to happen that is made visible when the film is developed. Before that developing, the image is invisible. It is called latent. A RAW file transcribes the number of photons received by each pixel on the sensor. It cannot be displayed and can be compared to the latent file that cannot be displayed until developed (chemically, in the case of film, by software in the case of digital).
During development, the film’s global contrast and brightness can be altered via changes in temperature, duration and agitation. Likewise, the global characteristics of the RAW file can be altered by an importation profile (the digital development phase) that alters white balance, exposure, contrast, HSL values …
Pixii RAW monochrome mode
Finally, the film can be printed under an enlarger, with local exposure and contrast adjustments made through techniques such as dodging and burning, among others. Likewise, local adjustments can be fine tuned in PP (and the global adjustments corrected) by hand or by presets, before exporting to a display format or printing.
In a way, capturing images in JPEG with presets applied in camera provides instantly usable results similar to using instant cameras. Note that this is no criticism. It takes only a moment’s look at William Wegman’s sublime large format Polaroids to see how stunning the results created by this approach can be.
So, why bother with RAW ?
The point is that, once the JPEG/Instant film image is created, it can only be altered with difficulty. As you can see on the images above, it doesn’t take much processing to bring a JPEG image to its limits. The result would be suitable for phone display or social media, but not for large screen viewing or printing.
Some users enjoy a get-it-done-in-camera approach, never touching a post-processing app after the shot is made. They are happy with Instant cameras, phones or JPEG output from high-quality digital cameras.
In contrast, we have designed Pixii for the photographers who like shooting as much as they enjoy revealing and fine-tuning their images in post-production. Getting it right, in this logic, means capturing as much information as possible to process the file to their personal taste.
This is why Pixii is first and foremost a RAW camera. This is our way of thinking: we prioritize RAW and we develop JPEG only as much as needed to provide a way to check photos, like on a phone, to make sure framing and focus are correct, for example.
However, for the same reason, we are making sure our JPEGs do reflect the advanced color profiles embedded in the RAW files. We try to make them as good as possible to represent the inner quality of the RAW file. But we do not try to interpret the image with added sharpness or tone mapping techniques and our full resolution JPEGs may feel less impressive than on other cameras. This is where we feel that the photographer should step in and take creative control.
Our philosophy lies with the open-format RAW called DNG. RAW files were designed to carry all of the sensor data to the editing software. This is where our R&D effort is spent. For example, we currently hold the DxOMark record score for APS-C cameras which is typically evaluated with RAW files.
Our dedication to RAW has also led us to create the world’s first color camera capable of taking a true RAW monochrome file. A plain B&W JPEG was losing too much of the sensor’s dynamic range, so we thought we could just compute the image illuminating the sensor, without the Bayer filter. And voilà: thanks to computing and RAW capture, Pixii photographers can shoot real monochrome digital negatives. And get to enjoy two cameras in one.
With RAW, we give the photographer access to the full camera sensor potential. And there is even more to explore!