- Capturing the image
- Camera settings
- Care and maintenance
- Custom functions
- Digital camera features
- Digital image file
- Digital image size and preview
- EOS MOVIE
- Exposure settings
- Flash basics
- Speedlite compatibility
- Speedlite range
- Speedlite zoom
- Flash on camera
- Dark backgrounds with flash
- Fill in flash
- Flash exposure lock and compensation
- Wireless flash
- Macroflash photography
- Bounce flash
- Flash synchronisation
- Stroboscopic flash
- Studio-style flash lighting with Speedlites
- Integrated Speedlite Transmitter
- Remote Release
- Focus points
- Image download
- Image compression
- Image information
- Image verification
- Introduction to digital photography
- Focal length
- All about apertures
- Lens speed
- Focusing and depth of field
- Black or white lenses
- Coloured rings
- Lens mount
- EF-S and field of view
- L-series lenses
- Fluorite, aspherical and UD lenses
- Prime and zoom lenses
- Image stabilisation
- Tilt and shift lenses
- Extension tubes
- Macro lenses
- Close-up lenses
- DO elements
- Fisheye lenses
- SubWavelength structure Coating
- Media cards
- Panoramic images
- Remote photography
- Scanning & copying
- Storage and archiving
- The digital darkroom
- White balance
Capturing the image: DIGIC processing
It is not only the quality of the camera’s lens and sensor that determines the quality of the image produced. Much of the credit must also go to the on-board mini-computer that processes the data from the sensor. Canon has developed the DIGIC (Digital Imaging Core) chip for this purpose.
The second-generation DIGIC II processor is used in many of the recent EOS digital models. It delivers excellent image quality, responsive camera performance, faster continuous shooting and extended battery life.
DIGIC II is able to handle the high-speed calculations needed to process huge volumes of data and provide exceptionally high image quality in real time. DIGIC II does not run as software, but as hardware built into the camera's circuitry. It consolidates the functions of a number of separate processing units to save time, space and power.
Most digital camera manufacturers face a trade-off between camera responsiveness and the amount of processing each image can receive. To overcome limitations with processor speed and capacity, manufacturers can install large and expensive buffers as a temporary store for unprocessed data, or compromise image quality by ‘dumbing down’ image processing, or both.
DIGIC II is designed to avoid these compromises. The processor is so fast it can read, process, compress and write JPEG image data back to the buffer between exposures.
Apart from the speed with which it clears data from the camera's buffer, the benefits of DIGIC II are most obvious in the areas of white balance (WB) adjustment. DIGIC II’s additional processing power permits more accurate calculation of auto white balance by taking into account factors such as orientation and subject position.
While other manufacturers use systems that divide the scene into hundreds of segments for white balance assessment, the DIGIC II processor has the time and power to look at tens of thousands of segments to build a complex plan of how the scene is constructed. This allows the camera to distinguish between more than one type of light source in a single scene and to treat each area individually for optimum white balance.
One of the benefits that has come about with the introduction of DIGIC II is extended battery life. As the processor is only operating for very short periods, it doesn’t use much power - DIGIC II is part of the reason that the EOS 5D, for example, is capable of taking 800 shots on just a single battery charge at 20 degrees C (based on the CIPA Standard and using the batteries and memory card format supplied with the camera).
DIGIC II has been a major feature of Canon digital cameras since the EOS-1D Mark II in 2004. DIGIC III retains the basic concept of DIGIC II and improves upon it with higher performance and faster speed. To cope with the very large signal processing required by the EOS-1D Mark III’s 10.1 megapixels and top continuous shooting speed of 10 fps, dual DIGIC III image processors are incorporated for parallel signal processing. The CMOS sensor reads out to the dual DIGIC III image processors simultaneously in eight channels.
By having two processors handle the workload, image processing is approximately 1.5x faster; CompactFlash card access speed is 1.3x faster, and SD card access is 2x faster, compared to the EOS-1D Mark II N. The extra power of dual DIGIC III image processors has also allowed analog-to-digital conversion to improve from 12 to 14 bits per channel, meaning that tonal gradation for RAW images is divided into 16,384 separate levels per channel rather than 4,096. When saved as a 16-bit TIFF image, the image retains the full range of tones obtained with 14 bits. Also, JPEG images, at 8 bits per color, are generated from the 14-bit data. This substantially reduces tonal skipping, improving gradation and overall image quality.
The DIGIC 4 processor first appeared in the EOS 50D camera launched in Autumn 2008 and is also featured in the EOS 5D Mark II. Compared to DIGIC III and the previous incarnations of DIGIC, the DIGIC 4 offers several advancements.
A more powerful processor can carry out more processing in the same time and therefore perform more advanced processing functions. The DIGIC 4 is actually about 1.3 times faster at signal processing when compared to a DIGIC III and this has several effects. It produces lower image noise for smoother images at every ISO setting and it also allows the extreme expansion (ISO) settings of H1 (12,800) and H2 (25,600) on the EOS 5D Mark II.
The extra processing speed also helps if high ISO noise reduction is enabled. The cameras can retain their burst rate and shooting speed in all but the highest level of noise processing.
Much of the DIGIC 4 processing is similar to the DIGIC III but it has also added some new features such as Peripheral Illumination Correction to counter the possibility of corner shading, Face Detection AF in Live View mode, and UDMA class 6 card compatibility.
In the EOS 5D Mark II it has added the ability to shoot full HD 1080p movie with sound because the processor can deal with the data fast enough to process it out to the memory card without bottle necks.
Overall, DIGIC 4 means that the cameras capture images with visibly better image quality.
The EOS 7D and EOS-1D Mark IV both feature Dual DIGIC 4 processors. The benefits are the same as having a single processor in the EOS 5D Mark II, but with two processors the processing speed is faster – this allows these cameras to deal with high resolution images at 8fps and 10fps respectively.
The extra processing power has also allowed 50 and 60fps HD movie recording at 720p as well as higher ISO capabilities, with the EOS-1D Mark IV featuring ISO expansion up to ISO 102,400.
First appearing in the EOS-1D X DSLR, the DIGIC 5+ processor is also used in the EOS 5D Mark III. The DIGIC 5+ processor takes the benefits of previous DIGIC processors and improves on them, while adding some new features.
DIGIC 5+ is 17 times faster than the DIGIC 4 processor which allows for faster data processing or higher resolution images, even at high frame rates. The combination of this processing power with the new sensor technology means images from the EOS-1D X and EOS 5D Mark III exhibit less noise than any previous EOS SLR cameras.
While DIGIC 4 provides the ability to correct for corner shading, DIGIC 5+ adds in-camera Chromatic Aberration Correction as well to ensure images are as sharp and clear as possible.
The DIGIC 5+ processor has also brought the ability to shoot multiple exposures in-camera, something that is not possible on other EOS models. The camera can overlay between two and nine images to create complex multiple exposure images. In the EOS 5D Mark III, the DIGIC 5+ processor also enables in-camera HDR shooting to capture extended dynamic range in images.
The processing power of the DIGIC 5+ also allows the use of faster memory cards, with full compatibility when used with UDMA 7 cards for faster write times and quicker buffer clearance.