In 1992, Leaf pioneered medium format capture with its Digital Capture Back (quickly nicknamed "the Brick"), which made a 12MB file on a 2×2cm Philips sensor. I saw the first results at Photokina that year and was immediately persuaded that the days of film were numbered. Nineteen years later, as Kodachrome finally bites the dust, Leaf is once again out in front, this time with an 80-megapixel 645-format digital back that delivers a 240MB file (eight-bit TIFF) measuring 10,320×7752 pixels.

The Aptus ll 12 carries a Dalsa-made sensor (53.7×40.3mm), which is housed in exactly the same shell as the other backs in the range.

A variant, the Aptus ll 12 R, allows this huge sensor to revolve 90º inside the housing. Having recently almost dropped a competitor's back while remounting it on an architectural camera, I would not hesitate to order this version.

Too many pixels?
The resolution of the new back is up in the stratospheric range that four or 16-shot studio backs deliver. But the critical advantage is that the data is captured in a single exposure. Four and 16‑shot backs can reveal the edge of a lettuce leaf beginning to curl under studio lights because of the slight delay between shots. But now, at the press of a button, say goodbye to the necessity for a 100kg studio stand on a concrete floor and flash packs that can deliver four exposures accurate within 10 percent, in colour, intensity and duration.

It also means that your subjects - models, liquids and a host of other mobile things - can be stopped in flight. In addition, of course, like all the other Aptus backs, the 12 is battery powered and completely self-contained, which adds portability to the mix, even though many such backs will likely spend their lives tethered to steamy Macs in a studio setup. A bunch of batteries and Compact Flash cards and away you go.

Moiré control - The screenshotshows the Leaf Capture interface, here showing a 100 percent view of an image of complex silk fabric - and a complete absence of Moiré. To the left, sliders to control the Moiré filter settings in the Adjust menu are visible. This image did not, in fact, need any such adjustment.

But who could possibly need so much resolution? The target market will be those who shoot fabrics and don't want the nightmare of Moiré, car photographers who need to capture all that smooth, shiny paintwork in careful detail, and advertising shooters photographing very intricate products and packaging with microscopic type.

It will also be useful to anyone who shoots large groups of people, or museum archivists with fragile manuscripts who require a facsimile in minute detail of every pencil squiggle or brush stroke of overpainting. And, of course, there is always the clamour from art directors to make the object tiny in an ocean of background so that fixing on the finished crop can be delayed until the last moment.

From this, one might assume that such huge resolution makes the Aptus ll 12 something of a rarified tool aimed at specialists, but it's also very desirable for more general use. I for one would add landscape photography to the list above, because resolving every leaf in a distant forest certainly challenged 10x8 film, and has eluded digital capture backs until very recently. This is probably the first digital device to comprehensively nail the problem of lack of fine detail in recording the great outdoors. That might also prove problematic, especially for celebrity portraiture, where an 80-megapixel back might prove unsuitable for older sitters - sadistic, even. That much resolution rendered by a sharp lens is way too forensic for any press agent to accept unless hours of flattering Photoshop surgery have been undertaken. That said, I would dearly love to photograph Mick Jagger with the Schneider Kreuznach LS 110mm f/2.8...

Willy the bulldog makes an excellent test subject with the 80mm Schneider Kreuznach standard at f/13 ISO 200 on a Phase One 645 DF camera, using the V Grip Air accessory to trigger a Profoto studio flash.

A 500x500 pixel crop shows the level of detail the back can capture. Pictures © Adam Woolfitt.

The same resolution overkill stricture is probably valid for most beauty shots, although that amount of detail deployed for groups of models or business executives in a studio setting could be very handy.

Lens kit
Squeezing the most out of your Aptus ll 12 inevitably depends on the performance of the optics of the camera system you use and, for this review, Peartree lent me a Phase One 645 DF camera with the three focal lengths that would probably constitute a "starter kit" for anyone investing from scratch: a 35mm, an 80mm and the manual focus 120mm Macro. Having tested Phase One's excellent 28mm lens (BJP #7775), which is both wider and sharper than the 35mm, that focal length would almost certainly feature in any second buying phase.

While the 35mm is a very nice general-purpose wide-angle - compact, light and fast enough (f/3.5) for most work - it is beginning to reveal its age under the brutal microscope of an 80-megapixel back. It has a whisper of chromatic aberration and very slight softness at the edges. The 80mm f/2.8 "standard" (what a misnomer!) is outstanding. It is one of an emerging series that employ bladed shutters designed by Schneider Kreuznach that can deliver super-fast flash synchro at 1/1600s in high ambient light. The 120mm Macro, with its extended helical, is of course manual focus only. All three lenses delivered excellent results but the 80mm, being the newest design and optimised for digital, proved remarkably sharp. Revised versions of the 35mm and 120mm Macro are on the drawing board and should come to market quite soon.

I also had the use of an Air Grip V that makes the Phase body very much easier to hold when shooting in portrait mode and contains a radio trigger for Profoto Air flash units. This is a very handy addition to the package, freeing the photographer from cables and extra bolt-on radio triggers. But it adds considerable weight.

Processor hungry
Leaf's proprietary format Mos (Mosaic) files are losslessly compressed on the fly, and average out at 95MB per image on a Compact Flash card. Each frame opens to ± 250MB as an eight-bit TIFF, so generating such huge files imposes heavy demands on the buffer in the back and on the host computer during capture, transfer and post-processing. Apart from a seriously fast computer, you will need a rack full of Terabyte storage drives. Data mounts up amazingly quickly, reminiscent of shooting in HD video.

ISO Test - Captured at ISO 50 with tungsten light using Schneider's 120mm Macro lens at 1/6s at f/9.

Excellent performance at opposite ends of the ISO range, 50 [left] and 800 [right]. Noise is well controlled at ISO 800, and colour remains almost identical. Resolution is compromised, but images remain very usable.

My new (and, as I thought) very well specified 17-inch Mac Book Pro has a 2.66GHz Core i7 processor and 8GB of Ram, but was still unable to capture when the camera was tethered. The minimum spec demands a 2.8GHz processor.

However, I was able to try the camera in tethered mode at Peartree's demo studio where it performed faultlessly, and where the V grip fired the flashes effortlessly. Files downloaded from a Compact Flash card to a 7200rpm eSata hard drive on my laptop took around 90s to process, using the latest (v.11.4) version of Leaf Capture software, which has now matured to become very easy to use, and now offering a huge range of sophisticated post-processing options. Files can be output through a number of preset profiles in RGB or CMYK and resized for purpose as they are exported.

From the back
The external appearance and interfaces of the Aptus ll 12 remain happily unchanged from earlier models. One of the nicest features of the Aptus range is the rear touchscreen with its dinky stylus stored in the upper edge of the back itself. Well-kept fingernails make an excellent substitute if the ARS director is picking his teeth with the stylus... The four initial menu options make it possible to select all functions that concern the back itself. Delving further down into the various menus reveals a wide range of functions. Apart from the obvious ones, such as setting the camera body in use, selecting white balance and ISO settings, it is possible to set up and name job folders, copyright notices and implant the photographer's ID. You can set and view grids and overlays, zoom in to 100 percent to view captures and tag files as firsts, seconds or rejects.

Video camera-type batteries fit underneath the back to power it and can be chosen with different capacities. When shooting tethered, power for the back is provided by the host computer. The video battery must first be removed to reveal the socket for the Firewire 800 cable, which is bespoke, with a long neck at right angles to the cable. Be warned - normal 800 Firewire cables will not fit.

The handgrip of the 645 DF camera houses six AA batteries that drive all the functions of the camera body. Woe betide you if either power source runs out on location as you will be left holding a £24,000 doorstop. I wrote in an earlier review that Phase One and Mamiya, which makes the body, should get to grips with the power system for this camera and provide a properly specified, sealed, rechargeable cell, fit for purpose. Fiddling around squeezing six AA batteries into a flimsy plastic holder is nobody's idea of fun, even on a Gameboy.

The camera springs instantly to life when turned on, while the back takes a rather more leisurely approach, taking about 10 seconds to power up and display the four-menu welcome screen.

Image quality
It is quite hard to adequately demonstrate the resolution available from the Aptus ll 12 back. If we were to publish an ordinary full-page shot, any crop that can demonstrate the real quality will be so tiny that a reader is unlikely to spot the marquee on the full frame. It becomes almost academic, since showing the difference between an optimal frame from a 54-megapixel sensor and an 80-megapixel model is only really visible at poster size or on a very good monitor.

However, I started by trying to provoke Moiré, one of the problems that Leaf claims such large files overcome. A particular silk blouse from my wife's wardrobe has proved a reliable test subject in the past and was wheeled out once again for the occasion.

Shot with available light on a good tripod, the back passed with flying colours. But even if it had not done so, the Capture software contains an extremely efficient set of Moiré filters that can be brushed over problem areas or applied globally to tricky images.

Museum quality - This is the kind of subject a museum might need to archive in extreme detail. These reverse appliqué panels are incorporated into the bodices of blouses and worn every day by the Cunah Indian women of Panama who sew them.

Close-up - The detail of the stitching makes an extremely good test subject, here captured with the Schneider 80mm lens with studio flash at f/14 ISO 50.

Conclusions
The grip proved an excellent addition to the basic camera and made holding it in portrait mode far easier. A built-in flash trigger for the Profoto Air system, which can easily integrate with other flash systems using a Profoto Transceiver, is the only wireless solution for the 1/1600s sync speed the bladed shutters in the Schneider Kreuznach lenses can achieve. Powered from either standard AA batteries or the Leaf digital Back batteries, this goes some way towards addressing my gripes with power for the camera. It also has a mini USB port for downloading camera body firmware updates.

I felt there were some rather haphazard engineering solutions in the V Grip. The example I was lent did not fit to the camera body well and was hard to tighten down because the knurled locking wheel only protrudes on one side of the casing. Even when fitted, there was a 1mm gap through which I could see the battery contacts inside the handle. A spot of rain would wreak havoc with the electronics if it found its way in. And finally there was some confusion about tripod threads, requiring a 3/8 to ¼ adapter at one stage. That's the sort of tiddly widget that gets left in the studio and can blight a shoot.

Version 11.4 is the newest iteration of Capture and it gets smoother with every revision. It now works very well, albeit slowly, unless installed on a very powerful computer. As noted above, eight-bit TIFF files took 90 seconds to process, but I observed that images shot at ISO 800 took quite a bit longer - proof that a lot of massaging is going on to process out noise and other artifacts in such files. The results are worth waiting for though.

The software and the back are beautifully integrated. Stable and as fast as can reasonably be expected when capturing and handling such mountains of data, tethered to a suitable computer the Aptus II 12 will capture a frame every 1.3 seconds until the hard drive bursts. Colour is very clean and commendably consistently across the range of ISO speeds.

Used with the latest optics in the range, it epitomises the very best that digital capture can deliver.

There are of course things that medium format will always struggle to do as well as a top-end 35mm DSLR system. It will be quite a long time before medium format can capture 10 frames a second at ISO 32,000, for example, or do HD Video. And by the time it can do that, who knows where 35mm DSLRs will have got to?
However, many really complex problems are now well within the competence of medium format, and a back such as the Aptus 12 should excel. Brilliant solutions for architectural photographers come in the shape of specialist rigid-bodied cameras such as those made by Arca and Alpa. Complex still-life studio images requiring geometric and depth control are easily handled by mini monorails such as those from Linhof, Silvestri and Sinar, while the new 120mm tilt-and-shift lenses for medium format from Zeiss will lend ever greater scope to a platform such as the Phase One 645 DF.

But not all is plain sailing, and I don't wish to adopt that most irritating stance of motoring correspondents who rave at length about a Bugatti Veyron but fail to mention that it costs £850,000.

All the cameras and options hinted at above cost lots of money and times are hard. But if you can only afford to work on the top rungs of the ladder, you should test the Leaf Aprus ll 12, because it represents the best medium format back I have yet tried. (Oh, and it costs £24,000 with a Phase One body and that amazing Schneider 80mm lens.)

Visit www.leaf-photography.com.

The Aptus back tested was kindly lent by Peartree Photo camera rental in London. Visit www.peartreephoto.com.