I took this picture with an Olympus PEN camera because it was small enough to tote on a day in NYC. I left my bigger camera at home. Somehow, I always do.
For most photographers trained in the 20th century, the universal standard was 35mm film. The size of the negative: about 35mm wide, and about 24mm high, or, about 1 inch by 1.4 inches. Serious professional photographers preferred larger negatives, and the 120 film format remained (and remains) popular: here, the negative is 2 1/4 inches square, or wider, several times larger than the 35mm film popular with consumers. Larger negatives offer superior image quality, but they also require larger and more costly cameras and lenses.
Digital Image Sensors
So film is old-school, Kodak is gasping for survival, and everyone’s shooting snapshots with their iPhones using a 5 megapixel sensor that’s the size of a your smallest fingernail. And, for most purposes, including posting pictures on Facebook and printing snapshots, the image quality is adequate–as long as you’re shooting in place that has enough light, and not too much contrast.
What’s a sensor? It’s a flat surface filled with a great many small light-sensitive receptors. There are two popular designs: CMOS and CCD. The difference between them is complicated, and explained here. http://en.wikipedia.org/wiki/Image_sensor
ISO and Sensitivity
In the film days, 400 ISO (or, if you’re older, ASA) film was four times as sensitive as 100 ISO film. In other words, using 400 ISO film instead of 100 ISO film offered benefits similar to using a lens with a large maximum aperture, perhaps an f/1.4 lens in place of an f3.6 lens.
The comparison is not a perfect one, though. Increased sensitivity often comes with increased grain, reduced detail, and lesser color quality / color clarity. Cameras that cost more than a few hundred dollars are fine up to about 800 ISO, but then, the image degrades. Newer sensors do a far better job in the 800, 1600 and even 3200 ISO range than older models. This is the push: buy a camera with better “low light sensitivity”–that is, with improved image rendition in the higher ISO ranges–and your 2012-vintage 16 MP camera will produce better images than my 2010-vintage 12 MP camera with its ancient two-year-old sensor design.
Megapixels and Sensor Size
Although camera marketers have latched onto megapixels as a way to justify different camera prices (a 10 MP camera costs more than a 5 MP camera), the number of megapixels on the image sensor should not guide you, at least not from the start.
Instead, focus on the size of the sensor. A “full-frame” sensor is the size of 35mm film–and requires a large, professional-quality body and accompanying lenses. For example the new Canon EOS 5D Mark III is a $3,500 camera that weighs about two pounds and occupies about 90 cubic inches, without a lens.
By comparison, an Olympus E-P3 uses a micro four thirds sensor that’s about 40% of the size, but it costs less than $1,000, weighs 11 ounces, and occupies less than 20 cubic inches, also without a lens.
In the real world of my life, I will not carry five pounds of camera, lenses and accessories with me everywhere, but I will carry a pound. If the image quality is acceptable.
Nikon, Sony, Fuji, and the Rest
In fact, several different sensor designs are becoming popular.
You’ve probably seen commercials and print ads for the Nikon 1 system, for example. It’s based upon a CX sensor format that’s about a quarter of the full 35mm frame. Image quality is good–and with the small sensor, Nikon has been able to manufacture small bodies (as small as reasonable ergonomics allow), and small lenses.
Sony’s small system is called the NEX, and they’ve already been through several generations their APC-S sensor system. The sensor size is somewhat larger than the micro four thirds standard, but somehow, this has resulted in an awkward combination of slightly larger lenses and slightly smaller bodies. The standard zoom, priced at $299, weighs about 7 ounces, but it’s about 2 1/2 inches wide and tall. This is a reasonable size for the lens, but the body is about 25% too small to balance the whole contraption. Fact is, APC-S requires a slightly larger body–16 cubic inches isn’t enough. Samsung, with its NX200, offers a seemingly more bulky body for an APS-C sensor, but, alas, there is no APC-S collective for that format, so Sony lenses are not compatible with Samsung lenses.
Fuji’s upcoming X-Pro 1 also uses a proprietary APS-C sensor for a wonderful new interchangeable lens system, but again, the larger sensor is associated with serious weight – the camera weighs a pound, occupies nearly 30 cubic inches without a lens, and operates (at a very high level) with (for now) just three proprietary lenses.
Panasonic and Olympus
Neither Panasonic nor Olympus are among the very largest camera makers, but they have benefitted from working together. By year end, there will be about 18 lenses in their micro four thirds format, each of them fully operable with significant advances in their micro four thirds sensor technology.
In fact, Olympus got off to a very good start with its earliest PEN cameras. Early on, the company’s engineers and management understood the importance of rendering accurate flesh tones, as well as a neutral, pleasing color palette. (Fujifilm and Nikon have also excelled in this quest.) By combining this special feature with the small size made possible by the micro four thirds format, PEN cameras quickly became a popular choice for serious photographers.
At this moment in 2012, Panasonic offers an extraordinary little micro four thirds camera, the GX1 ($699) that weighs just 11 ounces, occupies less than 20 cubic inches, and offers very impressive image quality with a 16 MB sensor. It’s filled with nifty features that will be addressed in the next article). This camera’s small size and wide array of available lenses and accessories makes it very appealing.
And yet, many photographers seem to prefer the slightly older Olympus E-P3, the current top-of-the-line PEN camera. It costs more ($899), and offers only a 12MB sensor, but the images are consistently excellent. This is not due to the number of megapixels, but instead, it is due to the right combination of engineering, aesthetic decisions during the design process (incorporating both lens and sensor design), and a corporate culture (a culture that has apparently remained intact despite gargantuan financial issues at the Board level).
This moment in 2012 (I am writing on the day after St. Patrick’s Day) is about to change. Olympus is reading its small 16 MP camera, the E-M5, and a new Panasonic GF-5 is also on its way.
The Whole Package
Of course, it’s not just the sensor and it’s not just the lenses that make a camera or camera system. It’s the overall design philosophy, most often captured in the design of the camera body. That’s what’s coming up next.
Digital Insider 
Please Comment