I thought for sure I'd already written a post called "The Point of Sufficiency," but a search doesn't turn it up, and I can't seem to find it under another name. So I thought perhaps I should just write it again, at the risk of repeating myself. This was triggered by one of Eolake's comments to the "High ISO High Noon" post, in which he said that when it comes to ISO speed, we always want a little more, and then a little more.
That's true—until it's not.
The idea is one that I've at least mentioned many times, for instance here. It's that in the history of photographic equipment and materials there have been various "competitions" or "races" to see which company can provide the most/fastest/best, but then in most cases a point of sufficiency is reached and customers decline to pay for further improvements.
This happened with film formats (film basically got down to 35mm size, which was small and convenient enough—further efforts to popularize still smaller formats all failed); lens speed (ƒ/1.4 was deemed sufficient by the market, with further increases in maximum aperture being rare and not especially popular*); telephoto reach (the "Olympia Sonnar" for the 1936 Olympics was a widely admired and popular achievement, but now, 1000mm and 1200mm lenses are mere curiosities); shutter speed (consider that the Nikon N8008's 1/8000th shutter speed was a big selling point, but the Minolta 9xi's 1/12000th was met with a yawn); fine grain in B&W films (Panatomic-X was enough; only a few fanatics followed the Tech Pan craze); reducing the size of SLRs was a brief race in the '70s (the Pentax ME was small enough); even build quality in cameras and lenses (the current market supports—barely—one carriage-trade brand. Beyond that, better build quality has not been rewarded with sales).
And so on.
Note that this is not a technical matter—it's a marketing matter. It has to do with meeting the need for what people want for as long as enough of us are willing to pay for it. The trend is for the race to continue among the manufacturers for as long as the buying public is rewarding the improvements. But sooner or later the buying public has what it needs, and has had enough, and stops wanting to pay for further improvements, and the manufacturers (save perhaps for one or two niche products in each case) basically give up the chase, and go try to find some other idea that will sell.
My prediction (which I've mentioned many times) is that this will happen with ISO speed in DSLRs, too, and with megapixels in Bayer-array sensors of the current type**. I don't know where the end point of either will turn out to be, and I don't know whether we have arrived at those points yet (is 24 MP enough? Is ISO 12,800 enough?), but history predicts that sooner or later, you will have enough and won't want to pay more for more.
Mike*People will trot out the example of the Noctilux or the Noct-Nikkor to refute me, but those never sold in significant numbers. One could even argue that with rangefinders, ƒ/2 was the point of sufficiency: the Leica 50mm Summicron always outsold the 50mm Summilux greatly, at least until Leica became primarily a status symbol. Before the introduction of the current Summilux-M, Leica decided that a new 50mm Summicron would have to be priced beyond even their market, but that a new 50mm Summilux could be supported. That's why the 50mm Summilux got a remake but the old Mandler Summicron soldiers on.
**The size of sensors is not just a matter of marketing, because there's a formidable technical stopping-point at 24x36mm that has to do with 35mm-legacy camera and lens design. So far, customers—core customers, at least, meaning enthusiasts—seem to find great appeal in larger sensors, up to at least 24x36mm. The next couple of years should indicate whether sensors larger than that are going to be rewarded with sales sufficient to support their continued development.Featured Comment by Eolake: "That's a very good point, and I'm sure you're right. One factor though, is that with many of the examples you give, further gain got punished by excessive size or price of the product. With megapixels or speed, this does not have to be the case. But of course, it will still be a case at some point of: how many people will need cameras which can make pictures that can be pin-sharp even blown up to wall size? Personally, with megapixels, I feel that 12 is a sweet spot. I do have a 21MP camera, but it's heavy and I only use it if I go for pictures I think I may want to blow up really big for my wall. With speed...this can go on a while yet, I won't mind. I'd like to never have to worry about shutter speed."