Manufacturing a product range focused upon APS-C and full frame (FF) ILCs is one of those strategic decisions that seems set in stone. If Canon and Nikon think it's a good differentiator for consumers, then it must be an industry standard that is broadly followed by everyone. However, the camera market is more nuanced than this and has some surprising origins. So, what is the best strategy?
To understand the digital sensors used inside ILCs, you need to understand film cameras. We take the 35mm industry standard for granted, although recognize that 60mm (in a range of aspect ratios) has played its part. Of course, we are talking about roll film here, whereas sheet film's most popular sizes include 4"x5", 5"x7", and 8"x10". So, where does 35 mm (and its peculiar 3x2 aspect ratio) come from?
George Eastman was one of the first to manufacture 35mm film using the new celluloid roll film format; however, that doesn't explain why it became the film standard. William Dickson's creation (while working for Thomas Edison) of the precursor to the movie camera — the kinetoscope — was the impetus for 35 mm with its 18x24 mm frames. Remember that the film strip was 35mm wide (possibly cut down from 70mm), or rather 1 3/8". In the kinetoscope, the film ran vertically with four perforations on each side for the film feed, giving an actual image width of 1" or ~24mm. Why was it 18mm high? Again, sticking with imperial units, Dickson appears to have experimented with 1", ¾", and ½". The square format would compositionally have been out of the question, while ½" would have been too small a frame size. It would seem that ¾" was the most logical choice for quality and was close to the 4:3 aspect ratio of the Golden Section. It also gave 16 frames per foot of film and so possibly 16 frames per second.
It was Leica's Oscar Barnack that really defined the format for stills cameras by cleverly turning the camera sideways to give a wide image frame (the 1913 Ur-Leica). The standard movie frame was doubled, creating a 36x24mm negative with eight perforations per frame. This was probably to simplify film transport using existing hardware but had the effect of changing the aspect ratio to the less than perfect 3:2. In the 1940s Nikon briefly tried the "correct" 32x24 mm with it's Nikon 1 rangefinder but saw little success.
Early DSLR Sensors
The earliest DSLRs, such as the Kodak DCS 200 onwards, actually used standard SLR bodies, replacing the film back with a digital version and then providing connections to the processor and storage. The camera doubled in size but was portable for journalists. These were top-shelf products (the DCS 100 started at $20,000), with the sensor one of the most expensive components, meaning that there were cost implications. This had to be offset against the crop factor this imposed relative to the 35mm lenses that were being used, alongside the resolution of the sensor. The 1991 DCS-100 had a 1.3 MP sensor measuring 20.5x16.4mm, giving a 1.75x crop factor. It was succeeded in 1992 by the smaller (13.8 x 9.2mm) 1.5 MP DCS-200 with a 2.5x crop factor. It would take until Canon's release of the 1Ds in 2002 for a full-frame sensor to appear in a DSLR (excluding the Contax N Digital), at which point Kodak followed suit with the DCS Pro 14n, which was also higher resolution and cheaper. Late to market, it signaled the beginning of the end for the DCS line.
This was a time of experimentation for DSLR manufacturers. Nikon's 1999 D1 (and subsequent D2) series went with APS-C sensors and had the advantage of being early to market. The writing was on the wall for Kodak, so what would Canon's move be? In 2001, it went with the low-key prosumer-oriented EOS-D30 using an ASP-C sensor, following it in 2002 with the pro-spec 1D featuring an APS-H (28.7x19.1mm) sensor inside (a small 1.3x crop factor). It went full frame in the form of the 1Ds in 2002, at which point its APS-C/FF lineup was set. Nikon wouldn't follow suit until the release of the D3 and D300 in 2007, using its so-called FX and DX sensors.
Meanwhile, Olympus released the Four Thirds system with Kodak, using a 18x13.5mm sensor, giving it a 2x crop factor, while both Pentax (with the *istD) and Fuji (through the FInePix S Pro range) went APS-C. Minolta's early entry into the digital market with the RD-175 had stuttered and the APS-C Maxxum 5D didn't arrive until 2005, then morphing into the Sony Alpha range.
Medium Format and Mirrorless
It might seem from the above that the APS-C/FF standard was already set in stone, but two seemingly distant developments shifted the focus. The first was a digital medium format which developed out of the emergence of medium format as the choice of many professionals where image quality was paramount and perhaps best exemplified by cameras from Hasselblad and Bronica. Using a modular design, it was relatively easy to retrofit a digital back; however, they remained relatively bulky compared to their 35 mm siblings. Pentax is notable for introducing the 6x7, a pro-specification medium format system that is still in production today; however, it was the prosumer level 645 that formed the basis for its transition to digital. Pentax wasn't the first to market with medium format digital — Leaf released digital backs in the 1990s, while Mamiya was the first to market with the ZD in 2004 — however, the 2010 645D was significantly cheaper than competitors and produced high-quality images. The 44x33mm sensor was becoming mainstream.
By 2000, the entire camera industry was about to pivot toward mirrorless beginning with Micro Four Thirds (MFT). Sony and Samsung quickly followed with the APS-C NEX3 and NX200 respectively, joined by Fuji (X-Pro1), Pentax (K-01), and Canon (EOS M) in 2012. There were two notably different product lines released in 2011. Nikon's 1 system used a CX (1") sensor (13.2x8.8mm), which was positively gargantuan compared to Pentax's first MILC, while the Q that had a 1/2.3" IBIS sensor (6.17 x 4.55mm). Both were compact systems with both manufacturers opting for systems smaller than MFT.
In reviewing the history of sensor sizes used in DSLRs, APS-C has dominated the market place and it's useful to remember that the name is derived from the ill-fated Advanced Photo System "Classic" negative that was introduced in 1996 and barely survived to 2011. The 25.1×16.7mm frame size has the same 3:2 aspect ratio as 35mm but takes us back closer to the original dimensions of the kinetoscope.
So, why APS-C? The dominance of 35mm is paramount here, as photographers' expectations and existing lens systems were built around it. It's therefore pertinent to summarize the impact crop factor has on the resulting image. For a standard 35mm lens, the image circle will extend beyond the sensor, essentially cropping it and so reducing the field-of-view, hence the name. For APS-C-designed lenses, this has the benefit of focal reach at the sharpest part of the lens and generally lighter optics and cheaper sensors. Depth of field also increases, which can be beneficial for certain styles of photography. However, the penalties include depth of field (if you want bokeh), the availability of wide angle optics, the greater impact of diffraction, and broadly noisier sensors.
APS-C is therefore sufficiently different from other sensor sizes to offer dual usage. Firstly, the smaller size benefits sports, wildlife, and street photographers amongst others. Secondly, it provides a lower barrier to entry for amateur photographers wanting to buy into a full camera system, yet can begin to approach the creative opportunities that full frame systems offer.
What Is the Right Strategy?
Sensor size is as much about differentiating markets as technical competencies. The FF/APS-C has existed for obvious reasons: it provided a reasonable compromise between capabilities that could be differentiated on price and segmented in to separate markets. Canon embraced this from the beginning with Nikon and Sony (Minolta) both following suit.
However, the search for commercial success has seen the exploration of a range of sensor sizes. Olympus and Panasonic have championed MFT as a better compromise, particularly for video and street/travel photography. With Olympus' future now in flux and Panasonic also championing FF, the future of MFT is uncertain. Nikon and Pentax both went smaller with the 1 and Q systems, which made a lot of sense at the time; with large, profitable, consumer sales, offering specialty cameras targeted at this market was obvious. Little did they know it would be usurped by the smartphone, which led to the demise of both systems.
Pentax stuck with APS-C for a long time, although we shouldn't forget the successful 645D (and 645Z), which appears to have been orphaned. It was late to market with K-1, which shows reluctance at embracing full frame. This brings us to Fuji, which has long stuck with APS-C from its early DSLRs through to the X-series line. As an early chip manufacturer, it has also tried to differentiate its offerings through the likes of the Super CCD and X-Trans sensor. It's therefore interesting that it chose to eschew full frame and go directly to medium format with the release of the GFX 50S in 2017.
Going forward, what is the right strategy? Crucial for camera manufacturers at the moment is the ability to stay relevant within the marketplace. Traditional users appear satisfied with the APS-C/FF orthodoxy. It suits current needs based upon their past use. However, that isn't how a market develops, and this is the reason to question Olympus' commercial viability. It's also why Nikon has canceled the 1 System and rapidly developed and released the Z System. Sony pivoted at exactly the right moment to capitalize on the changing market, while Fuji has been successfully low key.
Does this mean a small format is gone? Quite possibly, not because the systems aren't technically excellent, but because the traditional marketplace of consumers has evaporated and only MFT filling the gap. That leaves prosumers (high ticket toys), professionals (such as the Olympus E-M1X), and video sectors; it remains to be seen what Panasonic will do. Having joined the L-Mount Alliance will it pursue a dual-sensor size, video-focused, strategy?
The bigger question to ponder is how much of a future APS-C has. If quality is the primary differentiator for manufacturers then offering larger sensors could be a means of achieving this. Fuji looks set to stick to their APS-C/MF strategy, but could we see any other manufacturers change? I have already mused about the potential for Nikon to offer MF in the Z-mount and while the E-mount is restricted, could Sony also offer MF within a new mount? Canon is perhaps the most embracing manufacturer and its entry into MF could spell an exciting era of development. Of course, there is one manufacturer that makes cameras across the three main sensor sizes and that's Pentax: has it got the foundations for future success?