An explanation by John Bellingham
(with info borrowed from various internet sources)
So, you’ve forked over at least $1000 (but probably $2000) for your first DSLR camera. You have more buttons, dials, and menus than you know what to do with, even after reading through the fat booklet that came with your camera and explains its usage in ten different languages.
It’s all you can do to understand ISO, shutter speed, and how less is more when it comes to aperture. This beast of a camera can produce files in a Raw format, whatever that means, but it also has the nice comfortable JPEG format that we all know and love.
Like most you probably happily shoot in JPEG for quite awhile – getting used to the myriad of options available to you. One day you look at that Raw setting and ask, “should I be using Raw for the best quality? What is Raw, exactly?”
An excellent question. First, let us define these two formats.
A Raw file is…
- Not an image file, per se (it will require special software to view, though this software is easy to get).
- At least 8 bits per colour – red, green, and blue (12-bits per X, Y location), though most DSLRs record 12-bit colour (36-bits per location).
- Uncompressed (an 8 megapixel camera will produce an 8 MB Raw file).
- The complete (lossless) data from the camera’s sensor.
- Higher in dynamic range (ability to display highlights and shadows).
- Not suitable for printing directly from the camera or without post processing.
- Read only (all changes are saved in an XMP “sidecar” file or to a JPEG or other image format).
In comparison a JPEG is…
- A standard format readable by any image program on the market or available open source.
- Exactly 8-bits per colour (12-bits per location).
- Compressed (by looking for redundancy in the data like a ZIP file or stripping out what human can’t perceive like a MP3).
- Fairly small in file size (an 8 megapixel camera will produce JPEG between 1 and 3 MB’s in size).
- Lower in dynamic range.
- Immediately suitable for printing, sharing, or posting on the Web.
- Processed by your camera.
- Able to be manipulated, though not without losing data each time an edit is made.
Since JPG compression is lossy compression, (the opposite of lossless), with every save you lose data. The loss is set up in a way that it tries to remove data the eye cannot quite see (two pixels with almost same colour and brightness). So every time you open a JPG, do something with it and save it as JPG again you lose data. That also means when you press the “rotate” button in windows, you already lose data (the image is opened, rotated and saved again).
These differences lead implicitly to situations that require choosing one over the other. For instance, if you do not have much capacity to store images in camera, then shooting in JPEG will allow capturing 2 or 3 times the number you could shooting in Raw. This is also a good idea if you are at a party or some other event after which you want to share your photos quickly and easily.
On the other hand, if capacity is not an issue at all (8 GB and 16 GB flash cards are getting cheaper every week, there are also 256 GB cards available) you might consider shooting in Raw + JPEG, just to cover all the possibilities. If you cannot or do not want to do any post processing, then you simply have to shoot in JPEG. Taking a picture in Raw is only the first step in producing a quality image ready for printing. If, on the other hand, quality is of the utmost importance (like when you are shooting professionally), and you want to get every bit of performance your DSLR can offer then you should be shooting in Raw.
Shooting in JPEG: When you shoot in JPEG the camera’s internal software (often called “firmware” since its part of the hardware inside your camera) will take the information off the sensor and quickly process it before saving it. Some colour is lost as is some of the resolution (and on some cameras there is slightly more noise in a JPEG than its Raw version).
The major actor in this case is the Discrete Cosine Transformation (or DCT) which divides the image into blocks (usually 8×8 pixels) and determines what can be “safely” thrown away because it is less perceivable (the higher the compression ration/lower quality JPEG, the more is thrown away during this step). And when the image is put back together a row of 24 pixels that had 24 different tones might now only have 4 or 5. That information is forever lost without the raw data from the sensor recorded in a RAW file.
If your camera can burst (shoot continuously for a few seconds) you’ll actually be able to shoot more shots using JPEG than Raw because the slowest part of the whole process is actually saving the file to your memory card – so the larger RAWs take longer to save.
Shooting in Raw: If you do shoot in RAW, your computer, rather than the camera, will process the data and generate an image file from it. Guess which has more processing power: your digital camera or your computer? Shooting in Raw will give you much more control over how your image looks and even be able to correct several sins you may have committed when you took the photograph, such as the exposure.
To take advantage of this you will certainly need to use some software on your computer to process the files and produce JPEGs (or TIFFs), the most common being Adobe Photoshop and Lightroom. Most of the time the automatic settings are
fairly decent, but you have the chance to change the white balance, exposure, contrast, saturation, and even calibration of the red, green, and blue guns or correct for lens aberration – all lossless.
If the white balance is off I have found that it is much easier to fix using the Camera Raw screen than loading the JPEG and manipulating that – the end result is much better as well. The richness, detail (sharpness), colour range and ability to adjust these settings end up being so much greater with a Raw file, even though what a Raw file looks like before processing is anything but rich and sharp.
Process Pros & Cons:
The Pros of RAW format:
- RAW is a digital negative holding all of the data captured by your camera providing you a foundational element to which to apply all of your edits to with no sacrifice of image quality.
- RAW file software editors allow you to quickly and easily change the output of your image such as adjusting exposure, white balance, noise reduction, image size (interpolation), saturation, contrast, levels, curves, sharpness,output resolution, bits/channel, etc.
- RAW file software editors allow you to load saved adjustment settings and some even enables users to batch process a group of files versus making changes to one file at a time.
The Cons of RAW format:
- RAW files take up more space on your camera’s compact flash card than other formats.
- RAW files require you conduct some degree of post processing via photo editing software to convert your image to an editable file type for editing, printing and/or online display.
- RAW file software editors have a learning curve, even if mild, and for the uninitiated can be intimidating at first.
- Batch processing and/or loading multiple files may tax slower machines and require more computer RAM to keepyour software running smoothly.
The Pros of JPEG format:
- JPEG is a file format that has been adopted as a standard and can be loaded in a variety of programs making display easy and simple.
- JPEG files take up less space on your camera’s compact flash card than other formats.
- JPEGs can be loaded easily by most all image editing software applications, requiring no intermediate steps.
- Most DSLRs enable you to choose what size JPEG files (S, M, or L) to save to your compact flash card when
shooting. This enables you to use smaller images that are easier to handle for email attachments, web display or as an alternate preview mechanism if your camera supports saving files in JPEG and RAW formats simultaneously.
The Cons of JPEG format:
- JPEGs are not a lossless file format. Each time the file is saved data is compressed, with some data being lost in the process. The net impact can be loss of colour saturation, colour range and sharpness.
- JPEG files reflect a one-time interpretation of your subject based on the settings of your camera (white balance, exposure settings and output resolution, etc.). Altering these settings and re-outputting a new file, as you can with a RAW file, is not possible. What you capture is what you get.
- Interpolating or upsizing an image initially saved as a JPEG can result in less than ideal results. Some 3rd party software applications can do this better than others, but you’re still dependent on using another software application to get the job done.
- With specific types of photographed scenes JPEG compression artefacts can appear in prints.
Considerations: When it comes to your photography, however, you are the ultimate decision maker on what is best. I recommend that, if you haven’t, you play with the RAW format. You certainly won’t harm yourself or your camera. In fact, a great test is to go out just to shoot something (even just in the backyard or around the block). Shoot several photographs under various lighting conditions using the Raw + JPEG setting on your DSLR (if it has that capability). Take them back to your computer and compare after processing the Raw files. Take into consideration your time in doing so and see if the gain is worth your extra time.
RAW vs JPG – the final discussion: The RAW vs JPG debate has raged on to the point where pretty much every photographer has been worn down, or left confused. It’s been done. But bear with me on this one. It’ll be quick,and convincing. Then we really are done with this. Here it is:
There is NO photographer on this planet that is good enough to get:
- correct white balance,
- correct exposure,
- correct brightness level,
- correct overall and local contrast,
- correct saturation,
- A good black point,
- Or anything else you’d like to add,
DURING the moment of capture, for EVERY situation they are likely to encounter.
You have no excuse to shoot in JPG (only) format, unless perhaps …
- You’re out on assignment in Afghanistan and need to wire your images through, or
- You’re shooting hundreds of portraits on location to be printed out immediately, or
- You really, really, really need the small file size of a JPG, or
- You shoot with the Fuji S2, that JPG machine, or
- Your phone’s camera is your choice of artistic expression, or
- Unless you have some other truly specialized need to shoot in JPG.
Other than that, there is no reason not to shoot in RAW. It has to be RAW. Always.
If you shoot in a studio, and have absolute control over the lighting, and colour balance, and have fine-tuned your incamera settings … then sure, shoot JPG. Knock yourself out. You are all set to shoot within one specific scenario. Great.
But let me emphasize my previous statement again: There is NO photographer on this planet that is good enough to get every aspect of the image quality correct during the moment of capture, for every situation they are likely to encounter.
This implies that you will have to do some kind of adjustment on your selected images in post-processing. And then you might as well use the file format that gives you the most latitude and control for your initial edit and adjustment … RAW.