Understanding RAW

In my travels I often discover many people don’t understand RAW files vs. JPEG files.  There are reasons for shooting in either or both and I’d like to discuss both.

Let me start with an analogy!  When we shot film we would get it processed and get our prints back (usually in a 4″ x 6″ format).  Think of the digital world this way:  FILM NEGATIVES = RAW and 4″ x 6″ PRINTS = JPEG.  If the lab handed you back your 4″ x 6″ prints and threw the negatives away and when you wanted to get enlargements you had to use your prints instead of your negatives what would you do?

Of course many of you have NEVER shot film and asked for it to be processed into 4″ x 6″ prints.  So let’s elaborate further.

RAW vs. JPEG

Today’s digital world is no different.  When you want to process your images you want to start with the original image capture where possible, this is the RAW file.  When a camera records an exposure of an image it ALWAYS captures it in its native RAW file format.  This raw image capture from the image sensor is a result of recording the amount of light that each pixel or photo site records.  What is different is how you have asked your camera to STORE the image results onto the memory card.  Advanced cameras (DSLRS, and some Point & Shoot) will allow you store the results as RAW while virtually every camera will allow you to store the results as JPEG.  If your camera is capable of storing images in a RAW format and you tell it to store them in as JPEG you are asking the camera to do a conversion to JPEG and throw away the RAW file (the same as asking for the 4″ x 6″ prints and throwing away the negatives).  It should be noted, ALL cameras start out by capturing the image in RAW but not all give you the option of storing the data in this format.

Image File Bit Level

Another but not so subtle difference is how each format captures the amount of data in the file.  RAW files are generally stored in either 12 or 14 bit format while JPEG are ONLY stored as 8 bit files.  Why is this important?  JPEG 8 bit files allow you to capture up to 256 levels (2ˆ8) of brightness per color channel where as RAW is captured at 12 or 14 bit providing either 4,096 or 16,384 bits of data respectively (depending on camera).  So you can immediately see why RAW is beneficial, it’s capturing significantly more data than JPEG.

JPEG Processing in Camera

So when you set your camera in JPEG here is what is really happening:

• The sensor captures the image in RAW and processes it into JPEG and throws away the RAW file.  This process occurs regardless of whether your camera is capable of storing the image in RAW or not.
• The camera applies whatever image processing you have asked it to.  For instance many cameras have several image settings (or called Picture Style) called “Vivid”, “Monochrome”, “Standard”, “Smooth Skin Tones”, etc.  You may also be able to set the Quality of the image.  When you set your camera to any of these modes the camera will process the image and “bake” those settings into the final JPEG image.
• Contrast settings are applied to the image.
• Color Saturation settings are applied to the image.
• The camera then stores the final result as a JPEG to the memory card.  This basically means the camera will process the 12 or 14 bit RAW image to an 8 bit image and store it as a JPEG file.
• NOTE: JPEG files are stored as compressed files to save space on your memory card and computer.  By definition most compressed file formats (including JPEG) are a lossy file format.  JPEG file formats look at the file and will throw away repetitive color information.  There are several levels of JPEG compression so the level of data (and image) loss varies depending on the level of JPEG compression.

RAW Processing in Camera

This is simple relative to JPEG processing.  When you shoot in RAW the processing is virtually non-existent.  The image is recorded on the sensor and immediately stored on the memory card.  NO image processing is performed and any camera settings (white balance) are stored as a reference only.  What the the camera is doing is saving information such as camera settings and tagging it with the image.  It is NOT actually applying those settings to the images themselves.  What the camera sees and records on the image sensor along with the additional settings are saved on the memory card as a RAW file (CR2 for Canon, NEF for Nikon, etc.)

Why I shoot JPEG

So why do I shoot JPEG?  The simple answer is I very seldom do.  Because JPEG files are smaller than RAW files I will shoot JPEG if I want a very fast frame rate in my camera and I’m afraid of filling the camera buffer.  For example, on a Canon 1D Mark IV can shoot 121 Large JPEGS vs. 28 RAW at 10 frame per second (fps).  So if I’m afraid of filling the camera buffer with more than 28 RAW in a few seconds than I will shoot JPEG.

This seldom happens!

If I were a newspaper photographer that didn’t need high resolution images then I would shoot JPEG.

Again, because JPEG are smaller than RAW, if I needed to quickly send images to a newspaper or magazine publisher I would shoot JPEG due to their smaller file size.

Advantages:

• JPEGS are quick and easy to use
• No special software required to process your images
• Smaller file size

Why I shoot RAW

Simple, I want the HIGHEST QUALITY image possible, PERIOD!  A RAW file contains the exact image information captured by the camera sensor, no less, no more!

Any camera settings set are ignored by the RAW file format.  They are simply tagged to the RAW file but are not applied to the image itself.  (i.e. white balance is tagged as a reference but is not “baked” into the image).  This means the white balance (and other settings) can be changed in the the RAW processing software used.

I can determine myself what contract, saturation, white balance, etc. settings I want to apply to the image.  This gives me ultimate freedom to apply my creatvitiy to the image as I recall it.

Of course the biggest reason is as I mentioned earlier, there is simply more data in the image to work with during processing (256 bit vs. 4,096 or 16,384 bits of data).  All you need to do is start cropping your image or pushing it for color information to understand the impact of this.

Other advantages:

• All conversions are done on a fast powerful computer at your convenience.
• You can get more image data available from the sensor.
• You do not lose any image data as a result of compressions (JPEG)
• You have more flexibility in image processing than the “baked” in camera processing of JPEG.

Final Thoughts on RAW vs. JPEG

And finally, because RAW files take more space and memory cards and disk space is CHEAP.  Don’t throw away that valuable image information.