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Posted on: 19-Sep-2007

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How Nikon improved sensor sensitivity:
If you haven’t figured it by now, new digital camera generations come out every two years. This is because the electronics and the sensor technology follow Moore’s Law which clocks the industry’s technical grow. So, it should come as no surprise that Nikon has come out with the D3 about 2 years after the D2X.
Now if you think the pixel race is over and there’s no reason to buy a new camera, you are woefully wrong. It is true that the pixel race is pretty much over. That’s because the best cameras today cover about 99% of all photography applications. So the game has shifted significantly from pixels to pixel quality.
You can see this if you take any point an shoot any digital SLR and compare images. The digital SLR will always beat the point and shoot. The reason is not the lens, it’s that the higher price you paid for the digital SLR largely went into the sensor and the accompanying processor that interprets the data off the sensor.
Sensor technology continues to improve by leaps and bounds and it won\'t be long to where no film can match its dynamic range (chromes have not been able to match digital for years). Digital is also has more color accuracy than film.* The more they work on digital, the better it gets, and it’s simple as that. So in a couple of years they\'ll have a D4 that\'s even better.
That said, why would you fork out the dough for a new Nikon D3? In the good old days of film there were two things that determined image quality: the lens and the film. The camera was largely just a very reliable box to hold both. It’s Nikon’s ability to deliver the highest quality at great value that put them on the global map of photography. Especially as Vietnam War photographers found them so reliable in a jungle war environment.
With digital, there are three things that largely determine image quality: the lens, the sensor, and the image processor. Lenses have gotten so good, that they are not the factor they once were in camera selection. So, I have found that it is the body that has become most important when it comes to image quality. I currently shoot with a Canon 1Ds, Nikon D200, and Nikon D2X. The images from each have significant look and feel differences.
The D3 is Nikon’s first full frame sensor, which they call the FX format. Now a lot of Nikon pros have wanted this just because after decades of thinking in 35mm it was difficult to change. Nikon fought this because large chip sizes have lower yields and so they cost more to make. This is why there’s typically a $30K price tag on medium format backs. So, being able to make a full frame professional level camera like the D3 and sell it for $5000, means they have made a major breakthrough in yield.
But that’s not all. The D3’s 36.0x23.9mm sensor with an 8.45 micrometer pixel pitch has slightly fewer pixels than the D2X. That means that cell pitch is significantly larger and that means lower noise and greater sensitivity right out of the box. Think of each cell in a sensor as something a bucket of atoms. Light strikes the surface of the sensor and individual photons strike electrons orbiting the atom. Ideally the electron gets knocked in a way that causes the voltage in the cell to rise, which is collecting these electrons.
In a perfect world, every photon creates a free electron and every one of these electrons is collected; no photons intended for another cell fall into it; and no electrons leak into the cell from the sensor’s substrate and adjacent cells. That would be the perfect sensor with zero noise. This is what sensor developers are trying to achieve, but it’s not a perfect world. So a bigger cell means more light will get to it – so voltage levels will be higher, and the ratio between this and what leaks into the cell (called dark current) will be higher (called the signal to noise ratio). Thus, noise is lower and you have a much cleaner image. It’s also why Nikon can up top ISO limits from 800 on the D2X to a record setting 6400 ISO on the D3. and it has an can extended range of 100-25,600 ISO.
Nikon has also added gapless micro-lenses over each cell to make sure photons do not stray from one cell the other. These so-called wild-photons cause color inaccuracy. So color noise will be inherently lower.
On top of this Nikon’s new EXPEED image processor uses 14-bit Analog to Digital Converters (ADC) with 16-bit processing. This ADC allows 16,384 levels of sensitivity compared to the 4096 levels of the old 12-bit ADCs. But older processors were only 11-bit, which is only 2048 discrete gradients compared to the 65,536 possible with the D3’s 16-bit processor.
Oh and for all you flash demand geeks, Nikon but to CF slots in the D3.
* That doesn’t mean film is worse than digital. It’s likely that the discerning eye will always be able to tell the difference. When film came along, the same kinds of arguments went on between painting and photography. It was a debate that raged well into the sixties and seventies. Photography was not accepted as an art form until the seventies. Also, painting didn’t go away. Now the same sort of arguments rage between digital and film and I don’t want to go there.
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About weQuest:
weQuest's are written by G Dan Hutcheson, his career spans more than thirty years, in which he became a well-known as a visionary for helping companies make businesses out of technology. This includes hundreds of successful programs involving product development, positioning, and launch in Semiconductor, Technology, Medicine, Energy, Business, High Tech, Enviorntment, Electronics, healthcare and Business devisions.

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