How many pixels are enough? That's the question that's most often asked by photographers contemplating the purchase of a digital camera. And can you ever have too many?
While resolution is an issue of considerable interest to amateurs, for professionals it can be a matter of success or failure. Photography is an increasingly competitive business, and if your rivals can produce better quality images, they're more likely to get the job than you - it's as simple as that.
This is less of an issue in wedding and portrait work, where many customers seem happy with the results they get from six to eight megapixel cameras, but when it comes to advertising and stock photography the ultimate file size can be extremely important.
Many professionals make sales through picture libraries as a way of supplementing the income they earn from commissioned work. But over the last couple of years stock agencies have become more demanding and discriminating when it comes to accepting images that have been captured digitally. Most, such as Alamy (www.alamy.com), for example, now insist that files be 48Mb and over without interpolation.
It may be a remarkable coincidence, but the ultimate file size you get from the Mark II version of Canon's EOS 1Ds is 47.5Mb, which is within a whisker of that magic figure. This means that for an investment of £6,000 - not an outrageous sum when you consider that a single image could easily return that in a year - the door could be opened to a lucrative career as a stock photographer.
In the studio, meanwhile, this incredible resolution means you can now match the quality of a 6x7cm film camera with a 35mm-style digital SLR.
But it's not only Canon's new 16.7 megapixel resolution that makes it a significant development. There's also the fact that it uses a CMOS sensor that's capable of producing images with little of the noise or chromatic aberration (fringing) issues that have dogged some other high-end digital SLRs such as the Kodak Pro14/n.
Add to that the full-frame capture you get from the 24x36mm sensor and you can see why the 1Ds Mark II is such a tempting proposition for professionals in all areas. Not only does this mean that your wideangles really are wide-angled, but there's no lens magnification to narrow the field of view.
Whether the 1DS Mk II will appeal to amateurs affluent enough to buy this is another matter entirely. This is a camera built without compromise. For a start, it's big and heavy; tipping the scales at over 2kg with a typical zoom lens and memory card.
Some 320g of that, the bottom 3cm of the camera, is accounted for by the battery, which is a heavy-duty cell that's good for 1,200 shots before it needs recharging. While it adds significantly to the weight, it's well worth it to know you're not going to run out of juice at a crucial moment when you're on location.
The EOS 1Ds Mark II is also stuffed to the gunnels with just about every advanced feature you could imagine. However, this makes it potentially complicated and confusing for those whose requirements are not so demanding.
For anyone wanting a '35mm' SLR with the ultimate current pixel count, Canon's update of its flagship model is in a class of its own. The increase from the 11.1 million pixels of the original EOS 1Ds to the 16.7 million pixels of the Mark II version places it fully at the front of the pack.
Focusing on the pixel count, however, can blind you to the many other reasons for buying the camera. In fact, listing all the features on offer would fill this review alone, so we'll only concentrate on the most exciting developments.
Where to begin? Well, how about the startup time and the speed of capture? Situations often change rapidly when you're taking pictures, and professionals need to be able to respond quickly.
With a start-up time of just 0.3 seconds, the 1Ds Mark II is ready to go immediately, so you never miss a shot. Even at its maximum resolution you can capture 32 images at a rate of 4 frames per second as JPEGs. This is more than sufficient for most situations, and even makes the camera suitable for some sports jobs and specialist areas such as fashion.
Images can be recorded to CompactFlash and SD cards - there are slots for both - but you'll need high capacity cards. If you decide to shoot in RAW for maximum quality, each file will take up around 14.6Mb. For everyday work the highest JPEG setting will do fine, but even then files are between 8Mb and 13Mb - depending on factors such as the subject, the ISO, and the processing parameters - and in our test we only got 83 shots on a 1Gb card.
Be prepared for the first time you view images from the 1Ds Mark II up on the screen - because if you haven't set any in-camera sharpening, they look rather soft. But implement a little Unsharp Mask in Photoshop and the true quality of the files jumps out at you. Use the magnifying tool to enlarge a particular area and you'll be amazed at the tremendous depth of detail - sufficient for images to be printed at A2 size and beyond.
The standard ISO range is 100 to 1600, but this can be expanded at both ends to 50 and 3200. The quality throughout is exceptional. At ISO100 to 400 noise is minimal and even at high settings it is more than acceptable.
When it comes to metering and white balance, the 1Ds Mark II boasts everything but the kitchen sink. And if it doesn't have it, then you probably don't need it!
The 21-zone Evaluative exposure that showed its worth on the original 1Ds is retained - and it's so accurate you really don't need anything else. But that doesn't prevent Canon giving you a complete set of options, including Partial (8.5 per cent), Spot (2.4 per cent), Multi-spot (averaging 8 different readings) and even good old Centre-Weighted. And on top of that, you get a memory lock, exposure compensation and bracketing.
Shutter speeds go all the way up to 1/8,000 sec, and the flash synch speed is 1/250 sec - ideal for subjects like weddings and portraits where fill-in flash may be required.
As with most professional SLRs, there's no built-in gun, but the camera is equipped with the latest E-TTL II flash metering control when used with a Canon EX Speedlite for almost total flash accuracy.
The auto white balance is pretty reliable as well, but once again there's all the overrides you could want, including six pre-sets, Kelvin settings and custom controls. Plus there are five user-selectable colour spaces, including sRGB and Adobe RGB.
The EOS 1Ds Mark II is fitted with Canon's well established 45-point auto-focusing system, which is blisteringly fast and bitingly accurate. There's the option to allow the camera to choose the focusing point for you, or you can do it yourself.
A professional camera needs to be reliable, and Canon has always had an enviable reputation in this area. Built around a tough water and dust-resistant body, the EOS 1Ds Mark II has a shutter durability of 200,000 cycles - enough to take 250 pictures every single day for over two years.
Despite its size and weight, the camera handles beautifully, with every control both easy and intuitive to operate. In fact, after a few days of use it begins to feel like an extension of your own hand.
At this moment in time there is no better 35mm-style digital camera on the market. However, it isn't a camera that will suit everyone and price is a real deciding factor. Some professionals don't need the enormous resolution it delivers and would be happy with the eight million pixel EOS 20D - which costs £5,000 less. Steve Bavister