A
ACR
Adobe Camera Raw: ACR is an image processing engine that is a common plug-in for Photoshop and Bridge. Lightroom uses the same basic ACR code as Photoshop and Bridge, but with extensions to used for the Digital Asset Management capabilities in the Lightroom catalog. For a more thorough description of ACR, check out this Adobe web page.
API
Application Programming Interface: a set of rules and tools that lets different software programs talk to each other. Operating systems have APIs built into them that can be used by normal application programs to provide the OS services to the application. This could be for things like reading and writing files, creating an application window on a screen and sending data to an application such as a database manager, running in the background.
D
DAM
Digital Asset Management: software used to store, organize, and share digital files like photos, videos, and documents. For more information on DAM, check out these pages from IBM and Wikipedia.
DCT
Discrete Cosine Transform (DCT). JPEG compression uses the Discrete Cosine Transform (DCT) to convert image data into the frequency domain, allowing for efficient data compression. This process involves dividing the image into blocks, applying the DCT to each block, and then quantizing the resulting coefficients to reduce file size. If your looking for more information, check out this page from Wikipedia.
demosaicing engine
A demosaicing engine is a digital processing algorithm that converts the data from the camera sensor to a full color image. It is also called color reconstruction, CFA interpolation or debayering. If you would like a more complete definition, check out this article from Wikipedia.
E
EXIF
Exchangeable Image File Format: A standard for storing technical metadata within a digital image file and audio files. The data stored can include such things as camera settings (aperture, ISO, shutter speed, lens focal length, etc), capture & location data (date/time, GPS location, etc), and device information (camera maker, model, etc). If you would like a more complete definition, check out this article from Wikipedia.
H
HDD
Hard Disk Drive: An HDD consists of several metal platters (mostly aluminum) coated with a very thin magnetic material. The platters are stacked onto the drive shaft of a motor that, for most consumer grade disk drives) spins at 5,400 or 7,200 revolutions per minute (RPM). The platters are sealed inside a metal case that also holds the read/write heads on arms that can be moved across the surface of the platters. Each head can read the contents of a single platter and write data to the platter. Currently available consumer-level hard disk drives come in sizes from 4TB to 24TB. If you would like a more complete definition, check out this article from TechTarget or this one from Wikipedia.
Huffman encoding
Huffman encoding is a method used for lossless data compression that assigns shorter binary codes to more frequent characters and longer codes to less frequent ones, making it efficient for reducing the overall size of data. This technique is widely used in various compression algorithms, such as ZIP and JPEG.
I
Internet Engineering Task Force (IETF)
The Internet Engineering Task Force (IETF), founded in 1986, is the standards development organization (SDO) for the Internet. The IETF makes voluntary standards that are often adopted by Internet users, network operators, and equipment vendors, and it thus helps shape the trajectory of the development of the Internet. But in no way does the IETF control, or even patrol, the Internet. Here is their web site.
IPTC
International Press Telecommunications Council: IPTC is a global standards body for the news media that defines popular data formats, such as metadata for photographs. This metadata is imbedded in the image file(s) and covers global data, such as photographer name, copyright information, title/caption, keywords and location where the image was taken. Check out the IPTC web site for complete details.
ITU-T T.81 / ISO/IEC 10918-1 (1992–1994)
The International Standard Organization standard for the JPEG image file structure. Their website can be found here.
J
JPEG
Joint Photographic Experts Group. Their website can be found here with a general information page here.
L
Libjpeg
A free and open source C software library that was the first standardized image compression method. The library includes three major core feature sets: 1) compression/decompression: full baseline and progressive codec support for jpg files; 2) APIs: standard libjpeg C API along with simplified memory-to-memory TurboJPEG wrappers; and 3) Utilities: command-line tools for converting files and performing lossless transformations like rotations, cropping and grayscale conversion. There are a number of forks of the basic library, including libjpeg-turbo (high performance, 2-6 times faster encoding & decoding) and Moz.JPEG (for optimizing jpg files to load faster on web pages while maintaining overall image quality.
M
metadata
This may sound silly when you first read it, but metadata is data about other data. For photographers, metadata usually refers to the information stored within image, video and audio files. Much of this information is put there as the camera creates the image file. It can include such things as the make, model and serial number of the camera, the make and model of the lens, the photographer’s name & copyright information, and lots of data about the exact specifications of the image, including shutter speed, f/stop, ISO, focus distance, exact lens focal length, whether a flash fired, what sequential image number this image is in all of the images shot with a camera, the image dimensions, a video length, and audio file length. Much of this data is standard across many (and sometimes all) camera manufacturers, but most vendors include brand and even model specific information that on only applies to their cameras or even one specific camera model they produce. Metadata is not a photography-unique term and is also used to describe data store in other types of files, including web pages and document files. Metadata is used by digital asset management systems, such as Lightroom, to help organize images and to make it easier to find a single, specific image within a large collection of images. Metadata is also called metainformation. If you would like a more complete definition, check out this article from Wikipedia.
MIME
Multipurpose Internet Mail Extension: Created in 1992 to extend the capabilities of email. MIME compliant email could now carry pictures, video and formatted documents (attachments). This is now used to identify all files sent on the Internet.
N
NAS volume
Network Attached Storage volume: Almost every computer has some internal storage used for programs and data. This is usually one or more HDD’s or SSD’s physically housed inside the case that houses the computer. This is call internal storage. It may also have external HDD or SSD disk drives attached via USB cables to the computer. These are external storage. They are still directly attached to the computer and stored next to the computer and have data transfer rates nearly as fast as the internal drives. NAS storage can be thought of as very similar to external USB attached storage space, except that is not connected directly to the computer. Rather, it is accessed over the network. This is the same network that you could use to access the Internet, or a printer located somewhere else in your house or connected to another computer in your house. Accessing the data from a NAS device is not as fast as accessing data stored on internal or external disk drives, but usually works quite well for large volumes of lightly accessed data. Think of the half a million images you have in your archives that you shot more than a year ago. You want to keep them all, but you only access them infrequently. NAS devices hold multiple disk drives that can be combined to provide a very large amount storage. The minimum number of disks a NAS device can hold is two and the maximum varies by vendor & model, but the largest consumer-grade NAS’s can hold 16 drives. So, a 16-drive system full of 24TB disk drives would yield 360TB of space, if built as a single RAID-5 set (don’t ask, that will probably be another article). That space can be divided into ‘volumes’. This allows for different types of data to be kept on the device, but separate and with specific total space so they don’t grow too big, and to provide security so that only the correct users and/or computers can access each type of data. NAS devices virtually always provide some level of redundancy (various RAID levels) that internal and external disk drives don’t give (at least not without some extra software or special controller card. This redundancy provides for continued access to your data, even when a disk drive fails within the NAS unit. If you would like a more complete definition, check out this article from Wikipedia.
NVMe
Non-Volatile Memory Express: is a fast storage protocol that connects solid state drives directly to a computer’s CPU using PCIe lanes. This provides extremely fast speeds (3,500 MBs to over 14,000 MBs) and very low latency transfers. Functionally, most systems see these as an SSD, but significantly faster and smaller than a standard SSD. The NVMe devices are normally an M.2 form factor, basically a small circuit board, roughly the size of a stick of gum (and many are only half as long as a stick of gum) that plugs into the motherboard of the computer. They are so small that most motherboards now have two slots to plug them in, even on laptops. If you would like a more complete definition, check out this article from Wikipedia.
O
OS
Operating System: The basic software that runs a computer, controls the hardware and runs the applications that the user uses. The most widely know operating systems used by the general public are Windows, macOS, Linux, Android and iOS. If you would like a more thorough definition, check out this article from Wikipedia.
P
preview cache
As you browse through your images in Lightroom, it builds small preview images of each of your source images in your Lightroom catalog. To save time later, Lightroom stores these preview images in it’s “preview cache“. That way, the next time you go through the same directory, it can save the time to generate the preview images and just show the ones it already created. The preview cache is a single directory, in the same location with several levels of sub-directories underneath it. As you add more images to your catalog and browse through them, it keeps creating more and more preview images. More images means more space for the preview cache. It is possible to fill up the storage device that holds your catalog. Lightroom does provide ways to clear out your preview cache.
Q
Quantization
Quantization is the process of mapping continuous or high-precision values to a smaller set of discrete, lower-precision values. It is a core concept across machine learning, signal processing and physics. If you would like a more detailed description and examples of quantization, check out this article by MathWorks.
R
RAID
Redundant Array Of Independent Disks: RAID uses a layer of software, or hardware, or both, to take a group of disk drives and combine them together using one of several techniques, to form what looks like a single, large disk drive that includes redundancy so that the failure of a single disk drive does not result in the loss of any data and no down time. Your data is still accessible, although with a slight to significant performance hit. Most versions of RAID also allow you to replace the failing or failed drive with a new, working disk drive without any outage. Once the system finishes rebuilding the data on the failed drive, the performance will go back to its previous level. There are seven commonly used levels of RAID. They are all described in this article from Wikipedia. Some provide better performance, but normally at the expense of needing more disks and/or disk space. Others utilize less disk space, but with potential performance degradations and one maximizes the space available, but at the expense of redundancy. There are also a significant number of hybrid and proprietary RAID levels available on selected systems.
raw file
Some image formats have been standardized across all platforms. This includes jpg’s, tiff’s and png’s. Virtually all digital cameras will produce jpg files. However, jpg files are stored in a “lossy” format. That is, some of the detail available in the camera have been sacrificed to compress the images so they require less storage. Almost all vendors on most of their cameras also provide their own proprietary format, call a raw image file, that keeps all of the detail that the camera’s sensor has, but at the cost of more space. However, when you get to editing a raw file in any image editing program that supports raw formats, your ability to edit that file into a highly detailed, better quality image is greatly increased. The choice of using jpg or raw format is up to the photographer and will depend on the types of images they shoot and what they intend to do with those images during the editing process. Some cameras can also save both a jpg & raw version of each image taken.
S
SAN storage
Storage Area Network storage: A storage area network is very fast, specialized network for connecting a pool of storage to one or more servers or pcs. It function much like a NAS, in that the storage space within the SAN can be divided into separate chunks to allocate to separate servers or pcs. It biggest differences are speed and cost. Instead of using the same network connections that are used for Internet and other access to a server or pc, it uses a dedicated, fiber connected network that is only used for passing data between the servers/pcs and the SAN device(s). This requires special cards in the server or pc to connect the fiber. The SAN device, like a NAS device, holds many disk drives to form the pool of storage. And like most NAS devices provides disk drive redundancy. However, the SAN device can also provide networking redundancy by connecting multiple fiber connections (coming from separate controllers within the SAN device) to separate controller cards in a server or PC. This provides additional capacity and speed between the devices and redundancy so that the failure of a single card (at either end) or a cable does not prevent access to the data on the SAN. As you can imagine, all of the speed, storage capacity and redundancy comes at a cost. A low level SAN setup will cost 10X or more what an equivalent amount of NAS storage will go for. Very few individuals have their own SAN storage array(s). They are really meant more for medium to large companies. But if you happen to have the money and technical skills required to setup and administer a SAN (or can afford to hire someone to do it for you) you can’t beat them.
sidecar file
A sidecar file is a small file, normally composed of normal text, that stores the editing instructions, tags, keywords, titles, copyright information, etc. for another source file. The base name of the source file & sidecar file will be the same, but source will have a normal extension, like .nef for a raw image from a Nikon camera and the sidecar file will a different extension. The most common sidecar extension is .xmp, used by all Adobe products and many produces from other companies. For some products, the only place this information is kept is in the sidecar file. So deletion of a sidecar file will cause all of the edits to be lost. Lightroom Classic keeps all of this information in the Lightroom catalog and optionally in a sidecar file for camera raw images, if the option is turned on to create/update sidecar files. The default is to not create sidecar files.
SSD
Solid State Disk drive: An SSD is a storage device, like an HDD, but instead of using spinning metal oxide platters with read/write heads to store the data, it uses flash memory, specifically NAND chips) that retain the data, even when the power is removed from the device. Since there is no rotational delay or transfer delay, they are significantly faster than HDD’s and don’t have the varying response & transfer times like HDD’s. Unlike HDD’s, they make no noise when running, use less power and are much more durable. Older versions of SSD’s were built in the same size as disk drives, mainly the 2.5 inch SATA HDD’s and either could be used with the same connections. Newer SSD’s also come in the M.2 NVMe stick shapes. SSD’s are more expensive then HDD’s of the same size.
storage cloud sync
Adobe provides Lightroom cloud storage as part their Lightroom plans. The amount of storage depends upon the plan. Sync automatically backs up your image library to the cloud storage and syncs your edits across the desktop, mobile and web versions of the app. This is a good video that describes how the Adobe Cloud works with Lightroom Classic.
X
XMP file
An xmp file (.xmp is the extension on the file) is a small text file used to hold information related to a single raw image file with the same name, but a different extension, such as .nef or .cr2. Adobe Lightroom and Bridge use these files to hold your ‘development’ information, tags, ratings and keywords, in addition to it being stored in the Lightroom catalog. An xmp file for Adobe is their version of a sidecar-file. For Lightroom, the xmp files are optional because the information is also stored in the Lightroom catalog. Bridge does store your editing information in an xmp file, so deleting them will cause Bridge to loose its’ editing information for a raw file.
Z
ZIP (file format)
ZIP is an archive file format. A ZIP utility program can combine one or more files or directories of files, into a single archive file that is compressed using a lossless data compression algorithm. The individual files can later be extracted from the ZIP file. This file format was created in 1989 and first implemented by the PZKIP file utility program from PKWARE, Inc. The ZIP format is still used widely around the world and the file format is supported natively within many operating systems, such as Windows, macOS, Linux and Android. If you would like to learn more check out this article from Wikipedia.
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