Digital File Types

 

 
The Basics from Your Digital Camera

Digital photography has reached a remarkable level of beauty and sophistication. The output from today's digital cameras are capable of reproducing an amazing range of color, subtleties of tone and detail. This is even more remarkable given the fact that, at their essence these images are nothing more than collections of million of sterile little zeros and ones. This week I want to briefly discuss how those digits are stored in image files and how the choice of the file type can affect the results of the final image.

The Basic Choice, Lossless vs Lossy 
There is a long list of image file types that are available, but only a few which are routinely used to record images within todays digital cameras. Most commonly these include JPEGs (.jpg), TIFFs (.tif) and various versions of RAW files. The choice of file type centers around two factors, image quality and file size and as is true for almost all of photography, the decision involves compromise. The highest quality image files (TIFF and RAW) record the photographic data with what is referred to as "Lossless"
algorithms that retain all of the information from the sensor. The resulting images are of higher quality, with optimal tonal range and less noise and they are less subject degradation during editing or copying. The only disadvantages of lossless images are their requirement for editing to reach their full potential and their substantial size. TIFFs and RAW images fill memory cards quicker and take longer to save. The longer save times becomes a significant issue when capturing bursts of images such as when shooting wildlife or sporting events.

JPEG Have Trouble with High Contrast Situations

The opposite of "lossless" are those file types that achieve smaller files by compressing and discarding the data. These are somewhat

JPEGs struggle to Salvage Detail in Shaddows

comically referred to as "lossy". Within digital cameras, JPGs are the primary example of this compressed format. JPEG algorithms reduce file size by throwing out data and reducing the tonal depth. Depending on the level of compression, the results are files which are much smaller, allowing quicker recording of bursts of images and room for more pictured on the memory cards, but there is a significant price to pay for the compression. JPEGs and other Lossy file types have poorer tonal range with higher noise and artifact. They stand up much less well to aggressive editing or repeated copying. Depending on the image's intended usage, this loss of quality may not be important, but, as we will see, it is important to understand how the choice of original file type affects your ability to reach your photographic goal.

Those are the basics, now let's look at the individual file types.

Lossless Files

Doing It in the RAW

Capt. Zerubbabel's Rest

Many, but not all digital cameras have the capability of recording images in "RAW" format. RAW files record the "naked" data from the sensor without any loss of tonal depth or color information. They are totally unedited within the camera, although the image that you see on the LCD screen is actually a JPEG rendered within the camera to allow for quicker display and a better sense of how the final image might look. RAW images are like film negatives. They contain the maximum amount of information from the sensor, providing the greatest capability to undergo editing and adjustments of brightness and color balance. RAW files are substantially larger than compressed formats, but given the inexpensiveness of memory and the greater processing speed of modern cameras, this is not a major disadvantage.

Capt Zerubbabel Snow returned to Chesterfield after fighting in the Revolutionary War
He died in 1795 and lies next to his father, John Snow, in the West Burying Grounds.
"Winter is Coming !"

 Perhaps the RAW file's greatest disadvantage comes as a consequence of its greatest advantage. The down side of the format's ability to be manipulated is that RAW files must be edited to reveal their true beauty. Unedited "raw" RAW files appear flat with low contrast and washed out colors. All the glorious potential is there but it must be brought forth in post-processing. For me this is he most exciting part of working with RAW files. It is akin to the darkroom magic of watching prints slowly appear from the developer bath, but if you want to snap the picture and be done, then RAW is not for you. All I can say is that if the quality of your images is important to you, then learning to work with RAW images is unarguably worth the effort.



Whose RAW is It Anyway?
There is no single RAW format. Each camera manufacturer has their own proprietary format and provides the software required to
edit it. Lightroom, Photoshop and many other photo editing programs can read

Spring Sentinel, Keene, NH

most of these formats, but every time Canon or Nikon comes up with a new camera or wrinkle in their format, the software companies have to scurry to catch up. The persistent question is, if a camera company disappears or looses interest, will support for their RAW files vanish as well. For this reason Adobe has created their own open source RAW format called Digital Negative ".dng". My standard workflow involves archiving the proprietary RAW files in a separate directory and then converting the files to DNGs that I use as my working images. It may sound complicated, but, happily, Lightroom can do it all automatically as I upload the files from my memory card.

TIFF
Tiff files might be more appropriately discussed among the various "output" file types, used to store and transmit images after processing, but some cameras have the option of recording images

Persistent Maple

in this format. TIFF (Tagged Image File Format) files are often used to store images since the image files are Lossless. Like RAW files, they retain all the information on brightness, contrast, color balance and saturation, but unlike proprietary RAW formats, TIFFs are universally accessible to essentially all editing software. TIFFs come in 8 and 16 bit versions with the same quality advantages in the 16 bit files. When used to save files edited in Photoshop, TIFF files have the ability to retain most of the layers created by that program, but this capability comes with a cost in file size. TIFFs can be gigantic, but this is less of an issue when the file is coming unedited directly from the camera. For me TIFFs are primarily useful when I want to send an easily readable, full resolution, edited image to a friend or client. When I want to record losslessly in the camera, I stick to RAW.

Lossy Files
 
JPG
JPG stands for Joint Photographic Expert Group and is the most

Central Square Gazebo, Keene, NH

common file type, found in essentially every digital camera. Again it uses a lossy algorithm to record image data into compressed files. JPEGs undergo processing within the camera including "Baking in" the color balance based on the camera settings. The resultant images can often look better than unprocessed RAW images, but this preprocessing limits the ability to make adjustments during editing in Lightroom or Photoshop. The level of compression of the JPG file can be adjusted, but in all cases the resulting images are reduced in tonal depth, usually from the RAW 12-16 bits to only 8. 8 bit images have only 256 tonal gradations for Red, Green and Blue as compared to more than 64,000 with 16 bit images. This difference may not be apparent in small images

RAW or JPEG, Makes Little Difference on the Web

designed for sharing on the internet, but it becomes strongly evident when they are manipulated in Photoshop or other programs, resulting in loss of detail, color banding and restriction of the ability to enlarge the image. Despite the loss of quality, JPEG is a popular format because the images come out of the camera requiring little if any processing to get an acceptable picture and because the image files are much smaller making them easier to store and to share.

The Quality Shows with Bigger Images

Size Matters
A full resolution, 21 megapixel RAW file coming from my Canon 5D Mark II is 25.8 megs in size compared to only 6.1 megs for a 21 megapixel maximal resolution JPEG. This means that more than four times as many JPEGs than RAW files can be stored on any memory card. It also means that, with the JPEG files, I can shoot a burst of 78 images before the camera will be forced to pause in order to buffer the data. In RAW I am limited to only 13 images in a burst. The choice of higher levels of JPEG compression has further impact on both the file size and image quality. At the highest degree of compression the file size drops to one megapixel, but, at a resolution of only one meg, image quality severely suffers.

Dancing Lady.  When trying to anticipate the action, JPEGs allow longer bursts of images.
For only the second time in years of shooting Stonewall Farm's "Dancing of the Ladies",
I caught a lady in full kick.

 

 

 

The Choice
It really comes down to what you want to do with the image after it leaves the camera. Modern digital cameras are remarkably sophisticated and, in unchallenging situations, do an excellent job

Many cameras can record image in two formats

recording images in JPEG. If your only goal is to grab that picture of the ham sandwich you had for lunch, and transmit it as quickly as you can, to as many people on the internet as possible, then JPEG is the way to go. If your goal is to go beyond the mere FACT of the image, and explore the remarkable quality and capabilities of modern digital photography, then RAW is the ONLY choice. And, when the situation arises, during post-processing, you can always compress that delicious RAW ham sandwich into the tiny JPEG that it truly deserves.

Jeff Newcomer
partridgebrookreflections.com