Monday, July 28, 2008

Does a 'modular DSLR' make any sense

Nikon Rumors: continues to debate the 'modular' DSLR.

The first serious camera I used was a modular camera - my dad's Nikon F1 Photomic. But that was built in the days when cameras were mechanical systems. Does a modular camera make any sense in the digital age?

The question is not only relevant to cameras, Norman asked the same question of mobile devices themselves in 'The disappearing computer'. So lets consider where modular makes sense.

Every professional DSLR is modular: lenses are interchangeable. Camera bodies develop over time. Lenses represent a substantial fraction of the cost of a complete camera and necessarily involve some form of compromise with respect to performance, weight, cost and focal length(s) supported. Even if cost were no object, a 14-400 mm f/1.4 constant aperture lens would be undesirably heavy and unwieldy.

Modular makes sense when:

1) Some parts of the system are likely to become obsolete over time but a significant fraction of the value of the system is vested in parts of the system that are likely to retain their value.

2) The suitability of the system for a particular purpose depends on a component supporting a range of functionality that cannot be adequately supported in a single instance using generally available technology.

Both criteria apply to cameras and lenses. Bodies become obsolete every 2 years or so but a lens design generally remains acceptably close to the state of the art decades after it is introduced. Professional photographers queue up to buy new bodies the day they are announced but few would consider it essential to trade in their lenses as aggressively.

So does a modular body make sense with respect to the first criteria? Well lets consider where the majority of the cost goes. In rough order of decreasing cost I would guess the breakdown would be something like: sensor, cpu, calibration, body, display.

The sensor and the CPU are both developing rapidly over time. There is no point in putting a 20MP sensor in a camera with a CPU designed to support a 10MP sensor. Bigger sensors will demand bigger CPUs. There is no particular advantage to using a lower resolution sensor with a higher capacity CPU. Modularity makes no sense on this criteria.

Neither the body nor the display vary markedly in ways that make support for modularity desirable. The design constraint of modularity would almost certainly negate any imaginable advantage here. Moreover each body is designed around a particular CPU and sensor combination. So modularity makes no sense on the second criteria either.

There is however one area where modularity might make sense and that is to allow the CPU capabilities of the body to be supplemented by an outboard CPU. This does not make a great deal of sense for taking still photographs but makes very good sense if one is shooting very high definition video.

I suspect that it is no coincidence that the Sony 12MP DSLR chip supports slightly greater resolution than the ultra-high definition 4K format used in movies. The 8Hz maximum frame rate is very close to the 24HZ minimum for persistence of vision.

Nikon has an unrivaled range of professional lenses. If it developed an F-mount body for cinematography it would probably become the industry standard in a very short period of time. Processing the raw data rate off the chip in real time is probably beyond what current generation processors could perform in real time but well within the capabilities of a high end PC workstation with modern graphics hardware.

If there is a 'modular Nikon' I would expect it to be a dedicated back for shooting high definition video for cinema with the job of capture delegated to a dedicated off-camera processor/storage module. The back would not be a DSLR back at all, it would be a multi-sensor 3CCD back designed to capture the video and perform lightweight compression to allow the resulting RAW feed to be captured to disk over a wired 1Gb Ethernet connection.

Such a device would cost upwards of $10K with $20K being the likely starting point, lenses being extra.

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