Making Peace With APS-C
March 19, 2010
It’s shocking to realize it was only six years ago when the first digital SLRs costing under $1000 arrived.
The original Canon Digital Rebel (300D) and Nikon D70 were the first to smash that psychologically-important price barrier. These 6-megapixel pioneers effectively launched the amateur DSLR market we know today.
But one argument that raged at the time—and which has never completely gone away—was about the “crop format” APS-C sensor size. (The name derives from a doomed film system; but now just means a sensor of about 23 x 15 mm.)
Was APS-C just a temporary, transitional phase? Would DSLRs eventually “grow up,” and return to the 24 x 36 mm dimensions of 135 format?
This was a significant question, at a time when virtually all available lenses were holdovers from manufacturers’ 35mm film-camera systems.
The smaller APS-C sensor meant that every lens got a (frequently-unwanted) increase in its effective focal length. Furthermore, an APS-C sensor only uses about 65% of the film-lens image circle. Why pay extra for larger, heavier, costlier—and possibly dimmer—lenses than you need?
Also, after switching lens focal lengths to get an equivalent angle of view, the APS-C camera will give deeper depth of field at a given distance and aperture. (The difference is a bit over one f/stop’s worth.)
But a more basic question was simply: Do APS-C sensors compromise image quality?
Well, sensor technology (and camera design) have gone through a few generations since 2004.
Microlenses and “fill factors” improved, so that even higher-pixel-count sensors improved sensitivity. (For one illustration, notice how Kodak practically doubled the quantum efficiency of their medium-format sensors between a 2007 sensor and the current one selected for the Pentax 645D.)
Today’s class-leading APS-C models can shoot with decent quality even at ISO 1600. And the typical APS-C 12 megapixel resolution is quite sufficient for any reasonable print size; exceeding what most 35mm film shooters ever achieved.
So it’s clear that APS-C has indeed reached the point of sufficiency for a the great majority of amateur photographers.
Still, Canon and Nikon did eventually introduce DLSRs with “full frame” 24 x 36 mm sensors. They were followed by Sony, then Leica. In part, this reflects the needs of professional shooters, whose investments in full-frame lenses can be enormous.
And for a few rare users, files of over 20 megapixels are sometimes needed. In those cases, a full-frame sensor maintains the large pixel size essential for good performance in noise and dynamic range.
But these are not inexpensive cameras.
So the question has never completely gone away: Is APS-C “the answer” for consumer DSLRs? Or will full-frame sensors eventually trickle down to the affordable end of the market?
I have mentioned before an interesting Canon PDF Whitepaper which discusses the economics of manufacturing full-frame sensors (start reading at pg. 11).
It’s not simply the 2.5x larger area of the sensor to consider; it’s that unavoidable chip flaws drastically reduce yields as areas get larger. Canon’s discussion concludes,
[…] a full-frame sensor costs not three or four times, but ten, twenty or more times as much as an APS-C sensor.
However, since that 2006 document was written, I have been curious whether the situation has changed.
Note that one cost challenge for full-frame sensors is the rarity of chip fabs who can produce masks of the needed size in one piece. “Stitching” together smaller masks adds to the complexity and cost of producing full-frame sensors—Chipworks was doubtful that the yield of usable full-frame parts was even 50%.
Thus, Chipwork’s best estimate was that a single full-frame sensor costs a camera manufacturer $300 to $400! (This compares to $70-80 for an APS-C sensor.)
And that’s the wholesale cost. What full-frame adds to the price the consumer pays must be higher still.
Thus, it seems unlikely the price of a full-frame DSLR will ever drop under $1000 (that magic number again)—at least, not anytime soon.
And actually, APS-C pretty darned decent.
It would have been nice if APS-C had somehow acquired a snappier, less geeky name—maybe that’s still possible?
But it seems time to declare: It’s the standard.