I've heard many people predict that some day all digital cameras will have "full frame" sensors like the Canon EOS 1Ds. Based on the laws of economics and physics, the opposite may be true. Here's why.

First, there is nothing sacred about the 24x36 mm frame size. The Simplex camera of 1914 was the first 24x36 mm format camera to be introduced in the United States. The “modern” 135 cartridge film was not introduced until 1934, but even that still has the same dimensions and perforation pitch as 35 mm movie film which was introduced back in 1892. Camera and film manufacturers had to standardize on a size so both could sell their wares. It just happened to be 24x36 mm. When you don’t use any film there’s not much reason to standardize on a format. The upper limit is the size of the image circle created by available lenses. The format can be any square or rectangle that fits inside the circle. The lower limit is how small the sensor can get while maintaining acceptable image quality.

When it comes to making solid state devices, statistics and the laws of physics say that miniaturization increases chip yield and reduces cost more than any other consideration. Huge chips like 24x36mm image sensors are incredibly expensive to manufacture and this is unlikely to change anytime soon, if ever. All other factors being equal, the laws of physics also tell us that larger pixels in an image sensor mean less noise and therefore a higher image quality. But, all other factors do not remain equal as time passes. Advances in other technologies allow manufacturers to constantly reduce the noise associated with any given pixel size. While bigger is still better (quieter), economics press manufacturers to minimize costs, and therefore produce the minimum image quality that is acceptable to consumers. Right now the acceptable quality level is roughly that of 35mm film, because it is what most photographers are used to. Camera manufacturers have, more or less, recently achieved that quality level. Because of this, I think the image quality we currently see in digital SLR cameras will increase only slightly, if at all. Speaking with their wallets, consumers have already said it's good enough. As time goes on it will be possible to achieve the same image quality with smaller and cheaper image sensors. Simultaneously, smaller, lighter, and cheaper lenses will be possible because they will no longer need to make an image circle that covers a 24x36 mm frame. Eventually, when our “film” lenses are starting to get old, one of the major manufacturers may change their lens mount to allow even smaller, lighter, and cheaper lenses that cover only the area of the then-tiny high mega pixel image sensors. If that happens, everyone will get mad about it and then go out and buy the new equipment.

We can already see this prediction evolving in Canon’s new EOS 20D. This camera packs 8 mega pixels into exactly the same sensor size as the 6 mega pixel EOS 10D. Noise figures for both cameras are about the same, but with 8 mega pixels the EOS 20D should be able to make large prints with roughly the same quality as 35mm film. This makes it as good as it needs to be in the eyes of most consumers. Consider too the huge investment made by many camera and lens manufacturers in tooling to produce “digital” lenses that have smaller than “full frame” image circles. These lenses are smaller, lighter, and cheaper than their “full frame” counterparts, and cannot be used on film cameras or digital cameras with large sensors unless you want photos with dark corners. Canon, Nikon, Olympus, and others now make these smaller "digital" lenses. With the recent introduction of two new EF-S "digital only" lenses by Canon, I suspect these lenses are harbingers of the future, not a temporary vision. All of these companies are betting that miniaturized sensors are here to stay, and they are the ones making the cameras.

We may see a limited number of “full frame” super-high pixel-count digital SLRs in the future, but I think these will never be the norm and will always have stratospheric prices. Of course we will continue to see digital frame rates increase, metering and displays will improve, and prices will moderate. Of course, I could simply be wrong about all of this...

Happy prophesizing!