If you put any faith in DxO Mark scores (and I do understand their limitations), today’s best $500 DSLRs make better images than all of the sub-$4000 cameras sold until 2008. Largely that’s thanks to some good recent APS-C sensors from Sony.

So I’m not sympathetic towards certain Pentax users, who bleat that they can’t make adequate photographs—not until the company delivers a DSLR with a 24×36 mm sensor. (With pre-Photokina Pentax rumors swirling, the issue is once again a hot topic for discussion.)

Full-Frame Pentax?

Full-Frame Pentax?

Yes, many long-time Pentaxians do have investments in full-frame “FA” lenses, ones that could cover the format.

But keep in mind, over the history of photography there have many camera mounts which died out entirely—obsoleting numerous fine lenses. How about Contax/Yashica mount? Minolta MD, or Canon FD? (Or even earlier systems, such as Exakta or the superb Zeiss Contarex?)

By contrast, any Pentax lens made since 1983 can at least be used on a modern DSLR—metering automatically, and with the benefit of built-in shake reduction. So the handwringing that some great lenses have been “orphaned” by Pentax can get a bit exaggerated.

Some point out hopefully that not long ago, Pentax introduced new telephoto lenses bearing the FA designation. Ergo, full-frame is coming!

But truthfully, no decent lens design even breaks a sweat in covering an image circle much smaller than its focal length. With a telephoto, full-frame coverage is basically “free”—so why not go ahead and use the FA labeling? It allowed Pentax to finesse the format question for a while longer; and maybe even sold a couple of extra lenses to Pentax film-body users.

I do agree with the complaint that the viewfinders of most consumer DSLRs are puny and unsatisfying. The view through the eyepiece of a full-frame body is noticeably more generous.

However, the electronic viewfinder of an Olympus E-P2 neatly solves this problem too—at a price savings of about $1400 over today’s cheapest full-frame DSLR. And the EVIL wave is only gathering momentum.

The perpetual cry from full-frame enthusiasts is that Moore’s Law will eventually slash 24x36mm sensor pricing. To me, this seems like a wishful misunderstanding of the facts.

The shrinking of circuit sizes which permits faster processors and denser memory chips is irrelevant to sensor design—the overall chip dimensions are fixed, and the circuitry features are already as small as they need to be.

Also, figuring the costs of CMOS chip production is not entirely straightforward. It costs money to research and develop significant new improvements over prior sensor generations; it’s expensive to create the photolithography masks for all the circuit layers. Then, remember that all these overhead costs must be recouped over only two, perhaps three years of sales. After that, your sensor will be eclipsed by later and even whizzier designs.

Thus, there is more to a sensor price than just the production-line cost; it also depends on the chip quantities sold. And full-frame DSLRs have never been huge sellers.

If APS-C sensors prove entirely satisfactory for 95% of typical photographs (counting both enthusiasts and professionals), a vicious circle results. With no mass-market camera using a full-frame sensor, volumes stay low, prices high. But with sensor prices high, it’s hard to create an appealing camera at a mass-market price point.

Furthermore, let’s consider the few users who would actually benefit from greater sensor area.

For the few who find 12 megapixels inadequate, nudging the number up to 24 Mp is not the dramatic difference you might imagine. To double your linear resolution, you must quadruple the number of pixels. Resolution-hounds would do better to look to medium format cameras, with sensors 40 Mp and up—which conveniently, seem to be dropping towards the $10,000 mark with the release of Pentax’s 645D.

The last full-frame holdouts are those who need extreme high-ISO potential. There’s no doubt that the 12Mp full-frame Nikon D3s makes an astounding showing here, with high-ISO performance that’s a solid 2 f/stops better than any APS-C camera. This is a legitimate advantage of class-leading 24×36 mm sensors.

Yet aside from bragging rights, we have to ask how many great photographs truly require ISO 6,400 and above. ISO 1600 already lets us shoot f/1.7 at 1/30th of a second under some pretty gloomy lighting—like the illumination a computer screen casts in a darkened room.

A day may come when sensor technology has fully matured, and every possible sensitivity tweak has been found. At that point, a particular sensor generation might hang around for a decade or more. So might those long production runs permit much lower unit costs for a full-frame sensor? There will still be a full-frame surcharge simply from the greater surface area and lower chip yields.

But who knows, perhaps it’s possible? By then we may have 40 Mp, 24×36 mm chips that are our new new “medium format.”

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.

Sub-$1000 DSLRs

New for 2004: DSLRs for Regular People

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?

Canon Full-Frame Sensor

Canon Full-Frame Sensor

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.

More recently I found a blog post from 2008 which sheds more light on the subject. (Chipworks is an interesting company, whose business is tearing down and minutely analyzing semiconductor products.)

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.

So let’s embrace APS-C. That means it’s time to reject overweight, overpriced lenses that were designed for the older, larger format. We need to demand sensible, native lens options.

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.

DxO Mark: µ4/3 versus APS-C

February 15, 2010

DxO Labs has released their sensor test results for two Micro Four Thirds cameras, the Panasonic GF1 and the Olympus E-P2.

Since DxO provides a handy comparison feature, here’s a link comparing both cameras with an APS-C sensor DSLR, the Nikon D5000.

DxO Labs Comparison, m4/3 vs. APS-C

Leading µ4/3 models versus typical DSLR

Note that the D5000 is Nikon’s second-cheapest DSLR, which you can get in a kit for $750. These two µ4/3 models cost more. (Although you can find the Olympus E-P1 for a bit under $700 now.)

I’m not “cherry picking” the D5000 for any particular reason (it is not the best-performing APS-C sensor DSLR). It’s just a current-technology APS-C model which matches the 12 megapixels of the µ4/3 models.

According to DP Review, the sensor used in the cheaper Pentax K-x is very similar.

But the larger, APS-C sensor simply means larger pixels (5.5 microns wide, versus 4.3). And if you click the “dynamic range” and “SNR 18%” tabs, you can see what a huge difference this makes.

For any given noise level, the APS-C camera gains nearly one whole f/stop of ISO sensitivity. The dynamic range is two stops greater.

As always with DxO tests, note that they evaluate just the sensor, based on raw images. They ignore any differences between different cameras’ JPEG processing quality, or any consideration of camera handling, etc.

Where Are The Lenses?

January 23, 2010

Most DSLRs today evolved from earlier film-camera systems. (Sony’s originally came from Minolta; only Olympus started over from scratch.)

Although lens mounts stayed the same, there was a tiny problem about the sensor. Film cameras shot in a 24 x 36mm format. But making digital sensor chips of that size turns out to be quite expensive and difficult.

Sensor chips are made on costly, ultrapure silicon wafers, each about 8 or 12 inches in diameter. Obviously, increasing the area of each sensor means fewer of them can fit on the wafer.

With all the steps needed to lay down pixel electronics, it’s nearly unavoidable to get a few random, chip-wrecking defects scattered across the wafer. So the bigger each sensor is, the more likely it is to be ruined by some defect.

These two factors mean the economics of “full-frame” sensors will always be forbidding. You can read more details in a rather informative Canon PDF white paper here. (Take their marketing spin with a grain of salt; just start reading at page 11.)

By Canon’s reckoning, a finished APS-C sensor might cost 1/20th as much as a full-frame one. (That was written in 2006; today’s numbers might be a little different, with 12″ wafers more common. But still, the principle applies.)

So, despite all the wails and begging of enthusiast photographers, there are still only a handful of 24 x 36 mm format digital cameras on the market. A Canon 5D Mk II is $2500. A Nikon D700 is $2400. A Leica M9 is a whopping $7000. A Sony A850 is the “bargain,” at only $2000. These prices are without lenses, of course.

Today’s affordable DSLR models are all based on smaller, APS-C sized sensors. The origin of that cryptic name is irrelevant today; but it simply means a chip slightly under 16 x 24 mm.

There are dozens of APS-C models on the market, starting from the low $400’s—and that price includes a kit zoom. Megapixel counts range from 6 to 14 Mp. While it would be misguided to push pixel counts higher than that, the current models give satisfactory images even when set to ISO 800.

It seems apparent that APS-C is today’s sweet spot for digital-camera value. And because of the chip economics I mentioned, that is not likely to change anytime soon.

So let me (finally) get to my real point.

Where are the lenses?

Where Are the Lenses?

Missing in Action: Interesting APS-C Primes

Back in the olden days of 35mm SLRs, the “kit lens” was typically a 50mm standard one, with an aperture f/1.8 or so. A photographer more serious about low-light shooting could buy the f/1.4 version. You could get a nice inexpensive wide angle or portrait lens of f/2.8 or faster.

So, where are the equivalents for APS-C?

Lots of old lenses designed for film bodies are still being sold. But when used on APS, these make you to pay a premium in size, weight, cost, and maximum aperture. Cameramakers have dragged their feet on creating interesting, new, fast lenses dedicated to APS-C bodies.

Today, of course, the default is to offer zooms instead of primes;  the APS-specific lenses you are able to buy are mostly zooms.

Yes, zooms are convenient. But you typically lose two f-stops of light-gathering power. Some say modern image stabilization gives back those two stops—but that’s true only if you don’t care about viewfinder dimness, or blur when the subject moves. Zooms are larger and heavier than primes, too.

The normal lens for an APS-C camera would be about 32 mm (48e on a 1.5x sensor; 52e on a 1.6x Canon). The only camera maker so far to “get it” with an APS-specific normal is Nikon, with their 35/1.8. Sigma sells a 30mm f/1.4 in various mounts—but it’s mystifying that they’re all alone in that market.

For portraits we generally want a nicely-blurred background—meaning we’d like a wide maximum f/stop. This is especially true when using a smaller sensor, because depth of field increases slightly compared to 24 x 36 format. So where are the APS-specific portrait lenses, at f/2.0 or faster? In the range of 60 to 70mm (giving 90-105e), there’s only this Tamron—intended more as a dedicated macro lens.

Yes, there’s oodles of 50mm’s around, recycled from the film era. Canon is well known for their “thrifty 50” —which apparently they’re able to knock out for a hundred bucks, despite it covering a larger format. Why on earth should APS-specific lenses be more expensive? The image circle they cover is only 2/3rds the width!

Shooting film, my most-used wide-angle is a 24mm f/2.8. And back in the day, cheap 28mm f/2.8’s were a dime a dozen. But convert that to APS-speak. Are there any f/2.8 lenses of roughly 17mm? Is your sole available choice one chubby $600 zoom? I sure can’t find anything else.

I’ll give credit to Pentax, for creating the widest lineup of APS-specific lenses—including several beautifully-finished primes. But their prices are high, and their widest apertures are really nothing to get excited about.

Finally, lets take a glance at the Micro Four Thirds universe, too. Panasonic’s new 20mm f/1.7 pancake (40e on the µ4/3 sensor format) has indeed made quite a splash.

The test reports are excellent. So I suppose it would be snarky to observe that Panasonic’s 20 just revives a lens style that numerous snapshot cameras offered in the 1970s—and at a much higher price.

So, where are the lenses?