The ABC’s of JPEGs, TIFFs, PNGs, and all those other extensions…
If you’ve taken a picture on a digital camera in the last 10 years, you’ve noticed when you load those images onto your computer, or print them out at the local drugstore that there are “file type” extensions like .jpeg or .tiff or .dng or .png and a whole host of others.
You’ve maybe even wondered “What the hell is the difference between a .JPEG and a .jpeg or a .gif or .tiff or…or…or…or…
Well wonder no more… This looks like a job for “Theoretical Thursdays” at Ikon Photographs! It’s where we do our best to demystify the science behind the art of photography…(That’s catchy, we should use that…)
At a glance, there are a few different file types…There are MANY more image file formats, but for the sake of clarity and keeping things relatively simple, we’re going to talk about the ones that you’re most likely to come into contact with. Let’s take a look.
Oh…Don’t get “Lost”…
Before we look at those file types…Let’s talk a minute about “lossy”…because it plays into the file formats… To keep information files somewhat manageable, computer engineers came up with two separate “algorithms” (formulas) for storing info…
–Yep, we started talking science and you started nodding off…
Images and Music are very similar in the world of digital information…
If you’ve ever dealt with music files, you might have heard about “lossy” and “lossless”…With images it’s somewhat the same case...
Lossless compression algorithms:
These reduce file size while preserving a perfect copy of the original uncompressed image. Lossless compression generally, but not always, results in larger files than lossy compression. Lossless compression should be used to avoid accumulating stages of re-compression when editing images.
Lossy compression algorithms
These preserve a representation of the original uncompressed image that may appear to be a perfect copy, but it is not a perfect copy. Often lossy compression is able to achieve smaller file sizes than lossless compression. Most lossy compression algorithms allow for variable compression that trades image quality for file size.
EARTH TO DAVE!
GET TO THE FORMATS!
Everyone is probably the most familiar with the term “jpeg”. But did you know…
JPEG (Joint Photographic Experts Group) is a lossy compression method; JPEG-compressed images are usually stored in the JFIF (JPEG File Interchange Format) file format. The JPEG/JFIF filename extension is JPG or JPEG. Nearly every digital camera can save images in the JPEG/JFIF format. JPEG applies lossy compression to images, which can result in a significant reduction of the file size. Applications can determine the degree of compression to apply, and the amount of compression affects the visual quality of the result. When not too great, the compression does not noticeably affect or detract from the image's quality, but JPEG files suffer generational degradationwhen repeatedly edited and saved. –That means, the more times you open a JPEG and do something with it and resave it, it loses more and more quality!
GIF (Graphics Interchange Format) is limited to an 8-bit palette, or 256 colors. This makes the GIF format suitable for storing graphics with relatively few colors such as simple diagrams, shapes, logos and cartoon style images. The GIF format supports animation and is still widely used to provide image animation effects. Its LZW lossless compression is more effective when large areas have a single color, and less effective for photographic or dithered images.
The TIFF (Tagged Image File Format) format is a flexible format that normally saves the file in a variety of “bit depth” –meaning how much ‘stuff’ is in each “bit” of information. The “tagging” refers to a variety of tagged or specifically coded information within the file itself. The tagged structure was designed to be easily extendible, and many vendors have introduced proprietary special-purpose tags – with the result that no one reader handles every flavor of TIFF file. TIFFs can be lossy and lossless; some offer relatively good lossless compression for black and white images. Some digital cameras can save images in TIFF format. TIFF image format is not widely supported by web browsers. TIFF remains widely accepted as a photograph file standard in the printing business. That means, if you can get your image into TIFF format, do so...Especially if you are going to get it printed.
RIF refers to raw image formats that are available on some digital cameras, rather than to a specific format. These formats usually use a lossless or nearly lossless compression, and produce file sizes smaller than the TIFF formats. Although there is a standard raw image format, (ISO 12234-2, TIFF/EP), the raw formats used by most cameras are not standardized or documented, and differ among camera manufacturers.
Most camera manufacturers have their own software for decoding or developing their raw file format, but there are also many third-party raw file converter applications available that accept raw files from most digital cameras.
Digital Negative (DNG) is an open lossless raw image format written by Adobe used for digital photography. It was launched on September 27, 2004. The launch was accompanied by the first version of the DNG specification, plus various products, including a free-of-charge DNG converter utility. All Adobe photo manipulation software (such as Adobe Photoshop and Adobe Lightroom) released since the launch supports DNG.
DNG is based on the TIFF/EP standard format, and mandates significant use of metadata. Use of the file format is royalty-free; Adobe has published a license allowing anyone to exploit DNG, and has also stated that there are no known intellectual property encumbrances or license requirements for DNG. Adobe stated that if there was a consensus that DNG should be controlled by a standards body, they were open to the idea.
The PNG (Portable Network Graphics) file format was created as a free, open-source alternative to GIF. The PNG file format supports eight-bit paletted images (with optional transparency for all palette colors) and 24-bit truecolor (16 million colors) or 48-bit truecolor with and without alpha channel - while GIF supports only 256 colors and a single transparent color.
Compared to JPEG, PNG excels when the image has large, uniformly colored areas. Even for photographs – where JPEG is often the choice for final distribution since its compression technique typically yields smaller file sizes – PNG is still well-suited to storing images during the editing process because of its lossless compression.
PNG provides a patent-free replacement for GIF (though GIF is itself now patent-free), and can also replace many common uses of TIFF. Indexed-color, grayscale, and truecolor images are supported, plus an optional alpha channel. PNG is designed to work well in online viewing applications like web browsers and can be fully streamed with a progressive display option. PNG is robust, providing both full file integrity checking and simple detection of common transmission errors.
The Exif (Exchangeable image file format) format is a file standard similar to the JFIF format with TIFF extensions; it is incorporated in the JPEG-writing software used in most cameras. Its purpose is to record and to standardize the exchange of images with image metadata between digital cameras and editing and viewing software. The metadata are recorded for individual images and include such things as camera settings, time and date, shutter speed, exposure, image size, compression, name of camera, color information. When images are viewed or edited by image editing software, all of this image information can be displayed.
The actual Exif metadata as such may be carried within different host formats, e.g. TIFF, JFIF (JPEG) or PNG. IFF-META is another example.
So…Next time you are asked about a “file format” for images…Bookmark this page! So that you can go back and say…Hey! I know what a .DNG is!!! I’ll send it to you as a .TIFF but only if you look at the .EXIF data!
Ok, so maybe we didn’t “demystify” much in this edition of Theoretical Thursday, but we sure did give you a lot of info…
Thanks for reading!!!