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Old Feb 21, 2005, 3:29 AM   #1
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I have been reading about digital camera sensor (CCD and CMOS) recently. I never realized there was so much difference in size between those in DSLR's and those in cameras with lenses that can't be switched out.

I am curious. Does anyone know how much these various sensors cost or where that information can be found?

How much does it cost Nkon to put the sensor in the D70?

How much does it cost for the much smaller sensor in the 8800?

Also, I am wondering. The 8800 sensor, despite its relatively small size, has 8 megapixels. The sensors on the low end DSLR's are much bigger but have 6 megapixels. What keeps camera companies from putthing in twice as many pixels?The density would still be less than on the 8800. I know some of the super expensive cameras have have twice as many megapixels, but ... Is it a desire to avoidnoisy images?

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Old Feb 21, 2005, 6:09 AM   #2
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robbo wrote:
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Also, I am wondering. The 8800 sensor, despite its relatively small size, has 8 megapixels. The sensors on the low end DSLR's are much bigger but have 6 megapixels. What keeps camera companies from putthing in twice as many pixels?
The problem isn't size, as you've noticed, and merely adding twice as many pixels won't necessarily help the quality. There have been a number of articles on the web about the Mars Spirit rover and the fact that its digital camera sensor has only 1 Mpixel of resolution, but takes pictures that would put our 4-5 megapixel prosumer cameras to shame. "spend your money on the optics" they say. Here are some excerpts from one article describing the issue:

"The technology used to make Spirit's Panoramic Camera, or Pancam, is essentially the same as what goes into a Casio or Pentax digital camera.
But the Pancam's lenses. . . are crafted more finely than anything you'd probably want to plunk down a Visa for. And the light-capturing . . . CCD, was manufactured with no tolerance for the minor flaws that are inherent in mass-produced consumer cameras.
Perhaps most important, the sensors on Spirit's CCDs are bigger. . .
A Sony DSC-F717, with a street price of around $600, has 5.2 million sensors (or 5 megapixels) on a chip that is 8.8 by 6.6 millimeters (or .35 by .26 inches). The Pancam has just a million sensors spread across a chip that's 12 by 12 millimeters -- nearly a half-inch square.
Each tiny Pancam sensor, measured in microns, is nearly four times as big as those on the Sony.
In the consumer market. . . 5-megapixel cameras often use the same size CCD as a 3-megapixel camera. More pixels are simply crammed onto the same-size chip.
"The pixels themselves get smaller," Myles said. "This has an impact on image quality."
Why? For one thing, smaller pixels are less light-sensitive.
Also, the lens quality might not support the additional pixels. As the receptors get smaller, a higher quality lens is needed to properly focus light onto each pixel. So where each pixel ought to capture different light information -- say perhaps a subtle shading change on the subject's cheek -- the same information can get spread across several pixels after passing through a lower quality lens."

http://www.space.com/businesstechnol...ed_040114.html


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Old Feb 21, 2005, 9:10 AM   #3
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Actually, the low end DLSRS are now at 8MP. But yes, just a year ago they were 6MP.

One of the problem is cost & yield. Yield is a term which refers to how many good things you make for a given unit of resources. The higher the "yield" the lower the waste, the more profitable your production line will be.

If you make something more complex (more MP) and you haven't mastered how to make it, you will have more failures. And having to throw away a sensor is expensive, especially if it has more physical materials in it. So one of the limiting factors in sensors is how well they can make them (and how cheaply you can make them.) Companies want a really high yield and I'm sure they make design decision that effect that. Also, yield goes up over time... you just get better at making the thing.

This desire to have a good yield goes directly up against being on the "cutting edge" of the technology and beating others to the market. It's a difficult juggling act.

You are right to think about the noise in the image as well. A "photosite" is the part of the sensor that actually senses the light. The more photosites you pack on the sensor the more they will interfere with each other. This contributes to noise. So as you crank up the MP, you have to get better at supressing the noise. This is not easy, but so far the big camera makers are doing a decent job of it. I wouldn't be surprised if camera makers could put more MP on a sensor than they do now... but they haven't mastered the amount of noise they'd get (just a guess.)

As to the cost of a sensor, I bet that camera makers don't want that information known. That would be very useful information to their competition. It would give them a target point to beat for their own sensor cost. I'd be surprised if you found hard numbers for that info.

Eric
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Old Feb 21, 2005, 5:38 PM   #4
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If I had to GUESS, I would say that these CCD sensors for mainstream cameras (say 5 megapixel 1/2.5") cost around US$10 for large quantities (or it might even be lower)....the DSLR sensors probably cost 5x that... You can probably find the cost information from thte sensor manufacturer sites (there are only like 3 or 4 of them) or more likely from a distributor...

Quote:

Also, I am wondering. The 8800 sensor, despite its relatively small size, has 8 megapixels. The sensors on the low end DSLR's are much bigger but have 6 megapixels. What keeps camera companies from putthing in twice as many pixels?The density would still be less than on the 8800. I know some of the super expensive cameras have have twice as many megapixels, but ... Is it a desire to avoid noisy images?
I think noise is definitely an issue. So is technology and costs. I think you WILL see more and more megapixels (as you can tell by some of the 2005 ultra-compacts models having 7 megapixels). I would expect 2005 or 2006 prosumers to be around 10 megapixels.
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Old Feb 21, 2005, 8:25 PM   #5
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Hi, guys. Thanks. I have a better feeling for the challenges facing digicam makers. It appears that optics (good lenses) are as important or more important than high pixel sensors. Who do you think makes the best lenses and on what cameras do you find them?



Thanks.
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