Handling & ease of use:
This heavyweight beast is made to keep going even when it's treated roughly. It's big, solid and heavy – in other words it's a working tool designed for pros who are going to put it through a punishing routine on a regular basis. Despite the weight, it is comfortable to hold thanks to the large grip on the right side and on the base, which is used when holding the camera vertically.
Like all its pro models, this Canon's push-button controls are unlike those found on consumer EOS models. While the control set-up will most likely prove daunting to DSLR newcomers, pro Canon users will be right at home with the top-plate controls. The rear array of buttons have seen a number of changes to make it easier and quicker to access major features and this updated system is pretty intuitive and along with the clean menu system on the large 3in LCD screen, makes camera operation quick and relatively simple for experienced SLR photographers. The viewfinder is excellent – the magnification of 0.76x and coverage of 100% makes for accurate composition and the screen is bright and clear, with exposure information along its base and an exposure scale, frame counter and battery indicator on the right. In summary, the MkIII handles beautifully.

Features:
The 21.1-megapixel CMOS sensor is the headline feature of the EOS-1DS MkIII, making it a real alternative to medium-format backs. It produces a maximum resolution of 5616x3744 pixels and very large file sizes: Raw files are 35Mb in size, while Large JPEGs are around 6.4Mb. Processing such large amounts of data requires the MkIII to boast two DIGIC III imaging processors. Despite the larger file sizes, it can process 4x faster than the MkII. It's able to handle Raw files at up to five frames-per-second for up to 12 shots and JPEGs for a sequence of 63 shots. And for smoother tonal gradation, the DIGIC III uses 14-bit (as opposed to 12-bit) signal processing.
The autofocus system boasts 45 AF points spread across the central area of the frame. These include 19 cross-type sensors, which offer enhanced AF with lenses of f/2.8 and faster. As you'd expect, there are several ways of setting up the AF system, such as to only use the 19 cross-type sensors or work with an inner or outer set of nine AF points. The exposure system is equally comprehensive and flexible. Choose from  63-zone Evaluative, centre-weighted average, Partial (8.5%) and spot (2.4%) metering patterns. The exposure modes are limited to the core four (Program, Manual, Aperture- and Shutter-priority) and Bulb, while there are various overrides (exposure compensation, autoexposure bracketing etc) and Custom Functions on offer for making further adjustments.
 There are three LCDs on the MkIII. The 3in LCD monitor is for viewing images and selecting functions on the on-screen menu, and offers Live View too. Below it is a small info LCD that shows which card slot is currently selected (there is one CompactFlash and one SD slot), White Balance, file type (Raw, JPEG) and file number. On the top-plate is a traditional LCD panel with key exposure information. The MkIII has a dedicated Ni-Mh battery that slots into the base at one end, while at the other are secondary controls (shutter button, AF points, AE Lock and AF-On) for when using the EOS vertically. Other features include Picture Styles (for tweaking the colour for landscapes, portraits etc), Highlight tone priority (to prevent burnt-out highlights), an ISO range of 100-3200 (expandable to 50-6400) and 57 Custom Functions.

Performance:
 The quality that's possible from such a large file size (JPEGs open at 60Mb) is nothing short of incredible. If you consider it's possible to get high-quality A3 inkjets from a ten-megapixel DSLR, you soon start to realise the potential that using a 21.1-megapixel gives a photographer in terms of image usage. For our test, we used a range of pro L-series lenses to really try to get the best from the sensor, including a 28-70mm f/2.8L, 16-35mm f/2.8L MkII and 70-200mm f/2.8L.
As our test images reveal, the level of detail is very high, resulting in excellent sharpness. It also means it's possible to crop and retain quality. Colour reproduction is very accurate too, with the Auto White Balance handling most lighting conditions, including mixed lighting, very well. Low noise at all ISO ratings is also impressive, with images at speeds as high as ISO 1600 producing more than acceptable quality.
The 45-point autofocus system works very well. In single-servo mode it locks very quickly and positively on the subject, while moving subjects are tracked well by the AI Servo. The EOS is a very enjoyable camera to use; it's fast and quiet and making your way around the camera is fairly easy once you're used to the layout. The 3in screen is excellent, with the on-screen menu system proving fast and easy to navigate. Reviewing images on the bright screen is easy too, with the magnification button and toggle stick allowing you to quickly zoom your way to check sharpness. One area where I did note the odd problem was surprisingly the Evaluative metering system, which occasionally underexposed scenes with weak backlighting. Apart from this though, I found the EOS-1DS MkIII a wonderfully capable camera that takes image quality for a 35mm-based digital SLR to new heights


FULL FRAME CMOS
The 21.1-megapixel CMOS sensor measures approx. 36x24mm, the same as a 35mm film frame. Each pixel is 6.4x6.4 microns. Its pixel resolution is far higher than other 35mm-based DSLRs and more like that of a medium-format digital back.

EF LENS RANGE
The EOS-1DS MkIII is compatible with over 50 EF lenses, but cannot be used with the EF-S lenses designed for EOS models using the smaller APS-C sensors. The full-frame sensor means that there is no effective focal length increase, which will be particularly appealing for wide-angle lovers

START-UP TIME/ SHUTTER LAG
It's worth noting how quick this camera is in operation. Switch it on and it's ready to shoot in 0.2 seconds, while shutter lag is a mere 55 milliseconds!

VIEWFINDER
The viewfinder is large, bright and sharp and provides around 100% frame coverage, which allows for very accurate framing. Our illustration above shows the arrangement of the 19 cross-type sensors within the AF array.

BATTERY PACK
Although more compact and lightweight than the packs used in previous models, the LP-E4 pack offers up to 1,800 shots from one charge!

SOLID CHASSIS
A rigid magnesium alloy body is at the heart of the EOS-1DS MkIII. The outer shell is protected from the elements by 
76 seals around the controls and cover seams to protect it from dust and moisture.

TEST VERDICT
The level of detail that can be recorded is incredible and it's really in a league of its own in terms of ability. It's far more portable than medium-format outfits and its range of advanced features, as well as the system of lenses and accessories at its disposal, really makes it a tempting proposition for pros looking for the best possible quality from a 35mm-based DSLR. But at £6,000, it's a very big investment and some serious thought needs to be given as to whether this expense over more affordable models like the EOS-1D MkIII or EOS 5D is justified. Those who can afford to buy this will find themselves with a DSLR that sets a new standard for image resolution.  In terms of image resolution, there is no other DSLR (outside of medium-format digital backs) that can match it.
Handling & Ease of use: 22/25
Features: 24/25
Performance: 23/25
Value for money: 23/25
FINAL SCORE: 92/100


Main  specifications

Model: Canon EOS-1DS MkIII
Contact: 08705 143723, ww.canon.co.uk
Sensor Type: CMOS
Resolution (Effective pixels): 21.1
Max Image Resolution (pixels): 5616x3744
Focal Length Increase: 1x
Number Of Increase: 45
Multi-Zone Metering Zones: 63
Standard ISO Rating: 100-1600
ISO Expansion: L:50, H: 3200
Card Format: CF & SD
RAW & JPEG: Yes
Shutter Speed Range: 1/8000sec to 30sec + bulb
Flash Sync: 1/250sec
Shake Reduction: IS Lenses
Dust reduction: Yes
Max Continuous Frame Rate: 5FPS
LCD Monitor: 3in
Power Source: Lithium –ion
Size: 156x159.5x79.9mm
Weight (Grams): 1210