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What is the best image storage format to use? This is a question that many a beginning photographer faces once they graduate into the world of the DSLR. What I love about the DSLR format is the flexibility these cameras allow. There are more options on these cameras than most photographers will ever use. One of the most basic of these is selection of the file format to save your photographs in on your memory card.
The choices you are faced with are RAW image format, JPEG in various flavours and TIFF. Each has its own distinct advantages and disadvantages
This is the native language of your camera, if you will. Each camera manufacturer has it’s own proprietary format for writing all of the image information that is captured onto the memory card.
The RAW image file contains all of the data from the image sensor, which is not yet processed and in no way ready to be printed or even edited on your computer. RAW image files are often referred to as digital negatives, fulfilling the same role in digital photography as negatives did in film photography. The negative was not directly usable as an image but contained all of the information captured by the camera. It had to be processed in order to be viewed as a print. Similarly, a RAW image must be processed before it is usable.
In order to process RAW image files, they must be downloaded into your computer and converted into another format. The usual program used for this are Adobe Camera RAW or it can be done directly on import into programs like Apple Aperture. These programs regularly update their library of RAW format codes from each camera manufacturer so that the exact dialect your camera speaks is computer readable.
One of the side bonuses of RAW format is that, along with the unprocessed format, a JPEG version of the image is also stored in the file. This makes it easy for you to view your photograph on your camera or for your image processing software to give you a preview of the photograph in the file.
RAW format files are very large and take up the most space on your memory card. They also take some time to process after the shutter is closed, so once the camera buffer is filled, there will be a slight delay while the camera writes the remaining data to the memory card. This can limit the maximum number of frames per second (FPS) that can be captured.
JPEG is an image storage format created by the Joint Photographic Experts Group and is familiar to anyone who has ever saved an image on their computer. It is a compressed file format designed to preserve the maximum amount of information by compressing the file into as small a storage package as possible. JPEG is also what is termed a “lossy” compression format because of the way it does the compression.
In order to compress a file, JPEG (and other compression algorithms) look for redundant sections of data in the file that can be thrown away (and replicated later when the file is opened). The problem with JPEG is that each time an image is stored beyond the initial writing of the JPEG file, some of the original information is lost. So if you make a JPEG of a JPEG of a JPEG, etc., each subsequent copy will be a poorer quality image than the original.
One of the things that most JPEG writers allow is a choice of the amount of compression that can be performed on the file when it is stored. On Nikon cameras this is reflected by terms as saving the file as Fine, Normal or Basic. Each version of JPEG has more compression and, hence, less of the original information actually encoded. Each version also has a different file size when saved, with Fine being the largest file.
On my Nikon D300 using an empty 4GB memory card I am able to save 360 images in Fine format, 719 images in Normal format and around 1400 images in Basic format. Because of the smaller file size of JPEG files, a higher sustained write rate from the camera buffer can be achieved and a higher FPS can also be sustained during a photo session.
JPEG files are almost immediately viewable by any camera or computer and can be printed directly from the camera. This is because the images are processed by the camera before they are stored. White balance, contrast, and other processing choices are pre-set in the camera menu and written to the file. Using JPEG storage removes much of the image processing choice from the photographer and gives it to the camera to make.
TIFF ( Tagged Image File Format) is a popular image storage format, widely supported by most image processing an manipulation programs and is computer viewable, just like JPEG. Where TIFF differs is that it is not a compressed image file, and so has none of the image quality degradation issues that JPEG suffers from.
Just like JPEG, the camera settings determine the nature of the image stored, although there is more latitude for subsequent editing of a TIFF file than there is for a JPEG file. In this respect, TIFF provides the best compromise between RAW format and JPEG if an immediate printable file right out of the camera is desired. The downside of TIFF files is that they are larger than the equivalent RAW file. Because of the file size, FPS rates are similar to that of RAW image shooting.
I find different types of photography need different treatments. I almost exclusively shoot in RAW format, except when I am shooting fast paced sporting events where I go to JPEG. The reason I do this is for the higher FPS I can shoot at in JPEG than in RAW and for the storage space on my cards. I will typically shoot 10 to 100 times as many images at a rodeo than I will at a portrait session so this is an issue.
The key to getting good JPEG images out of camera is to realize that the camera will be processing the image, so special attention should be paid to the image processing settings in the camera. Then good technique should result in more keepers than stinkers. A little experimentation will allow you to set up your preferred image treatment and then you can go blow your brains out at a high FPS rate.
I have not yet found an application where I would choose TIFF format over RAW or JPEG. RAW files have the maximum amount of processing flexibility in my editing software.
It is not a religious conviction you are making in choosing one format over another. Each has its utility and I will use the one that best serves my need. How about you? What is your most used format for your images? Let us know in the comments.
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