Portal:Technology
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Introduction
Technology plays an integral part in modern photographic processes. From the sensors capturing light falling on them, through the computers processing that data to the printers producing the final image - all of these processes are governed by a variety of different technologies. The following sections detail the more significant technologies, and their ramifications on the way we work.
Image Capture
Sensors
In this digital age, the imaging sensor used by cameras plays the central role in forming the images being captured. The technologies that make this possible are covered in the following articles:
- Types of Sensors
- CCD - One of the oldest designs, charge-coupled devices are still one of the leading types of image sensors.
- CMOS - A newer type of imager that allows engineers more flexibility in designing the sensor than the older CCD design.
- LBCAST - Similar in design to CMOS sensors but using a different type of transistor in their underlying design to help decrease noise levels.
- Foveon X3 - A proprietary technology that allows image sensors to read all three colours in a single photosite.
- Filtration
- Bayer Pattern - Allows inherently monochromatic image sensors to capture and interpret colour information.
- Infrared Filter - Filters infrared light out of the exposure so as to reduce its effect on the final image.
- Anti-Aliasing Filter - A special filter that adds a small amount of blur to captured images in order to prevent aliasing artifacts.
- Sensor Technologies
- Microlenses - Tiny lenses placed above each photosite in order to maximize the sensitivity of the imager.
- Electronic Shutter - Used in some types of image sensors, electronic shutters eliminate some of the limitations imposed by mechanical shutter assemblies.
- Readout Channels - Independent lines that allow image data to be pulled off of the sensor. High-end cameras generally have multiple channels to speed up the rate at which this can occur.
In-Camera Processing
When image data has been captured by the sensor, it must be read out and processed by the camera's microcontroller. The following articles cover the processing stages in this process:
- Readout Process
- ADC - The Analog-Digital Converter is a critical component in the readout process that takes the analog signal generated by the image sensor and converts it into a digital signal for processing.
- Demosaicing - The process used to take the monochromatic image generated by the sensor and convert it into a colour image.
- Whitebalance - The process of correcting for the colour shifts caused by the light source that is currently illuminating the scene.
- Sharpening - The process of correcting for softness generated by the Anti-Aliasing Filter used by most digital cameras.
- File Formats
- JPEG Files - A common file format used to store processed images in a compressed format.
- RAW Files - A method of storing image data with only minimal processing applied to it. This allows photographers to defer many settings for the post-processing steps, allowing more control over the photographic process.
Data Storage and Transfer
Once image data has been captured and processed, it must be stored so that other devices can retreive the results. The systems that handle these processes are covered in the following articles:
- Camera Buffers - High-speed volatile memory within the camera that holds image data before it can be stored on the memory card.
- Memory Cards - Large capacity non-volatile memory used to store image data for later retrieval by computers or printers.
- Formats
- Compactflash - A larger form of flash memory common in high-end DSLRs.
- Secure Digital - A type of flash memory with a very small footprint and used in many different types of cameras.
- Memory Technology
- Microdrives - Miniature hard drives providing large capacity memory cards at relatively low prices.
- Flash Memory - Solid-state non-volatile memory that can provide high performance and reliability.
- Formats
- Data Transfer
- Interfaces
- Protocols
Image Processing
RAW Conversion
When using a digital camera's RAW mode, the files must be put through a set of processing stages to produce a usable image. There are many different ways to go about this process, so different RAW conversion packages produce different results at different speeds. As such, these technologies are critical to anyone using this type of image.
- Processing Steps
- Demosaicing - The process used to take the monochromatic image generated by the sensor and convert it into a colour image.
- Tone Curves - The mechanism used to correct for differences between the way digital sensors see light and the way the human eye interprets it.
- Exposure Correction - As RAW files contain more tonal detail than can be recorded in conventional image files, they allow limited exposure correction in post processing.
- Whitebalance Correction - As whitebalance settings are applied after the RAW conversion process, this process provides complete control of the whitebalance settings after the fact.
- HDR Imaging - HDR imaging expands the available dynamic range of an image by combining the results of a number of images captured at different exposure settings.
- RAW File Formats
- NEF - Nikon's family of RAW file formats. Note that this is not a unified file format, so explicit support is required for each camera model.
- CRW/CR2 - Canon's family of RAW file formats. As with NEF, these formats are not unified so explicit support for individual camera models is required.
- TIF - Some older digital cameras store RAW data in conventional TIFF files. Note that the actual RAW data is stored in proprietary blocks within the file, so explicit support is required for each camera make and model.
- ERI JPEG - A patented mechanism used by Kodak to combine the functionality of RAW files into JPEG images that can be read by conventional software.
- DNG - A non-OEM RAW file format produced by Adobe with the intention of generating a standardized format for these images.
- Software
Metadata
In addition to the image data itself, most file formats allow the inclusion of additional related data. This data can store anything from the exposure details in the image, to the GPS coordinates it was shot to credit and captioning information. In many workflows, this information is a critical component to keeping things organized.
- EXIF - Industry standard metadata format used by nearly all digital cameras to automatically store information about the image in each file generated by the camera. Stored in a binary TIFF-style header and is a major component of nearly every image file format.
- IPTC - A set of standards used to store captions, credits and indexing data in image files. While there is no explicit standard for embedding this data, the mechanism used by Photoshop has become a defacto standard.
- XMP - Next-generation metadata format using XML-based headers to allow many different types of metadata (including all of the fields in EXIF and IPTC headers) to be easily stored. While stored in a less efficient manner than other formats, it's extensible architecture makes it much more flexible.
- ICC Profile - Colour profiles can be embedded directly into the image files, allowing software to automatically retrieve information about the colour space used for the main image data.
- GPS Data - Some high-end cameras allow the storage of GPS position data in the EXIF header of image files. This allows the location where an image was taken to be recorded for future reference.
Colour Management
Colour is one of the most fundamental variables in any image processing chain. As such, how the computer interprets and handles these values is extremely important. Please visit the dedicated colour page for more information on these technologies.
Misc. Processing
In addition to all of the above image processing groups, there are also a number of more conventional steps that photographers must be familiar with. These processes have been in use for many years, but are still an integral part of forming quality images. Please read the following articles for more information.
Storage and Archival
Storage Media
Storing images over the medium and long term is a critical challenge for many of today's digital photographers. Central to that problem is selecting a storage medium that provides the necessary resources to meet the goals of the photographer. These articles discuss many popular storage media, and the technologies related to them.
Cataloging
While keeping image files intact is an important consideration, just as critical is keeping them organized so that they can be found when needed. There are many different ways to approach this problem, and the following articles cover many of the more significant technologies involved in this space.
Output and Display
Display
In order to evaluate the images that have been captured and processed, display systems must be used to convert that data into something the human eye can interpret. The following articles discuss the technologies used in this area and how they relate to the display of digital images.
Printing
Once images have been captured, processed and stored the next step is generally to produce prints of that final work. Digital printing technology has evolved rapidly over the last decade, and the following articles cover the details of many of those used in modern printing systems.
Internet
In addition to traditional mechanisms, the Internet is becoming an increasingly important venue for displaying photographic works. This is purhaps one of the most rapidly changing areas of photographic workflow, so a solid grasp on the technologies at hand is critical for photographers working in this space.
See Also
- Computer Technology - Additional articles on computer technology and it's relation to photographic workflows.
- Camera Technology - Further information on technologies used in modern digital cameras.
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