|Written by Stuart Dennison|
|Thursday, 13 January 2011 10:00|
Three years after Sigma’s first TRUE-based camera - the DP1 - landed on UK shores, the DP1x & DP2x unify the range of three cameras with the faster TRUE-II processor and "Analog Front End" ADCs. The key component in the processing pipeline, Fujitsu and Sigma developed the system which handles most of the functions of a Foveon-based camera including LCD display, card interface and of course, raw processing.
With Sigma’s SD1 just around the corner, and reputedly sporting twin TRUE-II processors, it’s time to have a look at processing and pipeline.
Every digital camera on the market today has some sort of ASIC (Application Specific Integrated Circuit) to handle processing and the basic functions of the camera - in essence, every digital camera is a computer of some sort and as with computers there are many factors that influence performance. Whilst many brands will label their chipset as their own, the chances are that if the sensor is of a given family and manufacturer then the processor behind it will be similar whether it’s called Bionz, Expeed or PRIME; where it differs is what software and supporting cast it is working with. Just as an iMac or Macbook Pro is seen as an “Apple” product with very different benefits, performance and cost to a Windows PC, whilst both are based on Intel processors, the software is key for many manufacturers. Fortunately they can all benefit from this shared expertise, mixing and matching their core processing with value-added features to distinguish products whilst enjoying mature, stable underlying code and UI guidelines.
Sigma is naturally a bit different. The original SD9 and SD10 remain a little enigmatic, but the SD14 was announced to be using an Analog Devices Blackfin DSP for processing - a non-application specific programmable DSP, in this case the 600MHz dual-core Blackfin ADSP-BF561. Blackfin processors can be found in all manner of devices - including synthesizers, which use them to model the behaviour of analogue and digital/analog hybrid instruments and then generate a waveform directly, and cars using them in process control, ECUs and entertainment systems. As a flexible, powerful solution the Blackfin processor is quite stunning - but it is not optimised for image processing only.
The work on the Blackfin was successful enough to match the performance of any competitor; that the marketplace had some difficulty equating the 4.5Mp output file with 14Mp of data to move affected reviewer’s interpretations of the camera’s performance, and the flexible nature of the DSP allowed Sigma to make fairly significant changes to the camera’s behaviour over the lifetime of the product. However, for the DP1 something smaller, less expensive and capable of supporting SD cards was required - enter the Fujitsu Milbeaut M4, or MB91680A-T. With an initial sample price of 4,000¥ per unit, the TRUE processor delivered a dedicated 3-CCD image processing DSP paired with two FR80 RISC cores, 64Mb NOR Flash for firmware and 128Mb SDRAM to provide the image buffer; the architecture of the Milbeaut incorporates dedicated processors for image data whereas the Blackfin needed more intensive “creation” of software equivalents (or modification of pre-existing libraries); the dual 32-bit cores run at 132MHz but as part of the “Milbeaut” family of processors Sigma will benefit from improvements such as smaller dies and value-added features as they become available. The latest variants of the M4 line include face recognition, 14-bit capture and 30fps VGA - the new M5 processor is behind Pentax’s PRIME-II and handles the processing for the 645D as well as the DSLR models, so Sigma has a good partner to work with.
It’s worth remembering that “made by” and “based on” do not necessarily mean “same as” - in the chipset industry, even if Pentax’s PRIME-II is made by Fujitsu’s fabrication facility and based on Fujitsu’s architecture, it might not be the the same as the reference chips they supply and could be simply based on licensed cores.
The second generation TRUE-II was announced with the DP2 - less information is available about this version beyond it reputedly running at a faster clock speed; from a user perspective the DP2 was a decent upgrade from the DP1 in performance and ergonomics. I, and others, predicted the DP1 would have to move to this hardware - and after the DP1s brought the DP2’s sensor to the line, the two models were finally united as the DP1x and DP2s. Meanwhile, the SD14’s replacement - the SD15 - utilised the TRUE II and latest refinements of the 4.5Mp x 3 sensor in a true DSLR; it also announced the introduction of a revised or new analog to digital conversion, called "Analog Front End". This first appeared in the SD15, then the DP1x and now the DP2x.
As we begin 2011 then, the line up from Sigma uses similarly refined Foveon image sensors and TRUE-II processors. In theory this should mean that the choice is purely about the lens options and format of camera you want to carry - 28mm equivalent, 41mm equivalent compacts, or 1.7x crop DSLR. The sensor results should be the same.