Wednesday, August 25, 2010

Canon 120 Megapixel Sensor: Just What The World Needs

Canon's 120Mp Monster

Taking the old notion that too much of a good thing is no good at all, Canon has just invented a 120Mp, yes, you read that right 120 MEGAPIXEL sensor in APS-H (1.3x crop) format.

Holy cow! That's a lot of pixels in a tiny space!

In its official press release, Canon stated that the sensor can shoot full HD video using just 1/60th of its surface area and is capable of 9.5 frames per second continuous shooting. The new sensor is praised for its ability to offer resolution that surpasses all film formats, its capability to offer photographers previously unheard of cropping ability, and the ability to revolutionize dSLR video capability. In all, the sensor offers 2.4x improvement in resolution over Canon's current high MP full frame cameras: the 5DII and 1Ds III.

Do we need all those pixels? Probably not. The problems created by such a sensor are twofold:

First, all of those pixels crammed onto a small sensor means extremely high pixel density, which is basically the relationship between the amount of pixels on a sensor and the size of the sensor itself. Example: let's compare two 12Mp cameras: a Nikon D3 and any generic 12Mp point and shoot. Okay, pixel density is all about the pixel count to sensor area ratio. So, the D3 uses a sensor that measures 24x36mm, the same size as 35mm film. So, divide the Mp count by area and you get a very low pixel density of 1.5Mp per sq. cm. pixel density, which is the lowest thing going. Next, compare the P&S camera, which will have a tiny sensor. The P&S pixel density for 12Mp: around 40Mp per sq. cm.

Okay, one sensor packs pixels more tightly than the other, so what?

Why it matters: signal to noise ratio. All electronic sensors have some background noise to them, this is just the function of it being an electronic device. Now, let's assume that the D3 and the P&S have the same inherent noise levels in the sensor. Being unscientific, let's say they both produce 5 units of noise. With its very large pixels, each individual pixel on the D3 captures a lot of light, more than enough to completely drown out the noise and produce a grain-free image. Let's say the D3 captures 100 units of signal to only 5 of noise, that's a difference of 95 units. Onto the P&S and its tiny sensor. To get the same amount of pixels into a smaller area, one must shrink the pixels themselves. Now let's say that the P&S pixel only captures 10 units of signal per pixel. That's a 10 signal to 5 noise ratio. Bottom line: the noise will be a lot more apparent in the P&S image. That's why P&S cams are terrible in low light/high ISO conditions.

Problem 2: lenses. With today's highest pixel count cameras over 20Mp, the lenses just can't keep up. Basically, in lower Mp days, one could stop down a lens to get optimal sharpness. Now, even at slow apertures of f8-f11, the images still look mushy. Why? The lens simply can't resolve all of the detail that the sensor captures. So, if a lens can't produce a crisp image at 20Mp, how on Earth is it going to it at 120Mp?

Those lens engineers better start getting to work!

Now, after all this griping, there is a very positive side to the 120Mp sensor besides the fact that there are no plans to put it into production (okay, done bashing the sensor now, promise!). The good news: Canon claims that the 120Mp sensor can shoot 9.5 frames per second. Obviously, a 120Mp image is a lot of data and for such a huge file (a 24Mp RAW file from a Nikon D3x is over 1GB) to be processed that quickly means that Canon must have one mega processor behind the sensor. What does this mean? If this ultra high-speed processing ability does trickle down into production models, the only real limit for continuous shooting may be how fast the mirror in the camera can physically move, not the amount of data the camera can process and write to a memory card.

Now that's some good news!
For more good news:
Yes, the Tokina 28-70 review is almost done

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