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by Bart Arondson

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So I just watched a review on the Sony NEX-7, which is 24MP in APS-C size.... I am a Canon user and I immediately think about the announced Canon Powershot G1X with almost APS-C sensor but at a lower resolution.

One question suddenly springs to mind :

Why has there not been a full-frame but low resolution sensor?

I have no knowledge of imaging sensors manufacturing, but I asked myself, "Would it make sense to create a cheap full frame sensor that is very low resolution?"

I figured it somewhat would make sense. For starter, great ISO performance, secondly, greater control of DOF.

These are not available to consumers without spending a significant amount into top-level photographic gears.

For example, if I create a full frame sensor that is 10MP in resolution, would it be cheap to manufacture? If not, what are the reasons that make full frame sensors so expensive? Would it still be expensive to manufacture such sensor if I make its resolution very low, like 10MP or even 8MP etc?

I know it is a theoretical question, but if Canon can offer a Powershot compact camera with full-frame sensor at 8MP for below $1000 (USD), I would definitely buy it!

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5 Answers 5

up vote 10 down vote accepted

As mentioned by the answers by @matt and @rowland, the price is directly linked to the the area of silicon used to create the sensor. Ideally a sensor with twice the area should cost about twice as much. Since all production of electronics on silicon (and other substrates) will have flaws, not all the produced chips/sensors will work. The yield rate (as it's called) is lower when the sensor is bigger, using the same production process.

Imagine a sensor A that is twice as large in both directions compared to another sensor B. That means you can make 4 times as many of sensor B in the same area of sensor A. But if you have one flaw in that area, you're still left with 3 usable sensor Bs. If you were producing sensor A you'd have to scrap that sensor. This means that the yield rate is much greater for smaller sensors, which adds to the price differences.

The smaller the chip/sensor the less area and higher yield rate, which means a much lower price.

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Sensor price is more proportional to the physical size of the sensor, than the number of pixels within it. There are full frame sensor with lower pixel counts on some of the older models (for instance, the first Canon 1Ds). It's worth noticing that the sensitivity is lower than modern sensors - not because the pixels are larger, but due to other advances.

There may be scope to make larger pixels, but it wouldn't necessarily be any cheaper.

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This is basically Moore's Law at work. Manufacturing technology for sensors follows the same basic rule as for any other chip: over time, the number of elements that can be put on a chip doubles for a roughly-similar cost. It may be slightly cheaper to continue using an established technology level since there are some sunk costs, but in general fabrication facilities get upgraded as new tech comes along. There's no big savings in doing it the "old way". The primary distinguishing factor is size, and that scales with area, and worse, scales nonlinearly because making a bigger area flawless is harder than making many smaller chips in the same space. So, bigger sensors are always going to be more expensive.

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Look at Nikon D3X vs D3S. They both have the same sensor size but the D3X has twice the resolution (25 MP vs 12 MP). The cameras are otherwise almost identical but the lowest resolution one is $5200 USD vs $8000 USD for the higher-resolution one.

The 25 MP sensor requires finer circuitry and therefore will have lower yields. At the same time there is a market for both because the D3S can produce images that are much cleaner but it wont print them as large. Its standard ISO range reaches 12800 (with boost to 102400) while the D3X has a standard range that maxes out at 1600 (with boost to 6400).

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Just to add one more interesting bit: once upon a time there actually was a relatively low resolution full-frame sensor. The Contax N was a six megapixel, full-frame design.

Unfortunately, despite the low resolution its low-light performance was pretty lousy (even compared to other cameras of the time). They seem to have more or less given up on getting it to autofocus well, and built in a focus-bracketing mode instead. Being a Contax, it was also quite expensive.

On the plus side, at ISO 100 or below it had probably the best 6 megapixel sensor anybody ever built, and the Zeiss lenses really are extremely good.

Bottom line: Contax dropped the N after less than a year on the market. Shortly after that, Contax dropped out of the market entirely.

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