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Old Dec 23, 2005, 4:51 PM   #11
Join Date: Jun 2003
Location: Savannah, GA (USA)
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Carskick wrote:
The only way I could see this happening is if the sensor got significantly larger. For example, if you had your 3MP had a 1/2.5inch sensor, you'd have to go up almost to a 1 inch sensor to maintain enough detail per pixel to make up for optical zoom. The 1/1.8" sensor in the SD550 is not going to have as much detail per pixels as a 3MP camera with 1/2.5".
A larger photosite for each pixel doesn't really capture more "detail per pixel" as you put it.

You're just storing a value for the color and brightness level for each pixel in the JPEG image after the demosaic algorithms (with each photosite only capturing a singal color, with the demosaic algorithms computing the final results stored for each pixel via interpolation algorithms).

Now, how well a photosite responds to light can make a difference (dynamic range of of the signal generated, sensitivity to light, accuracy of the signal level generated).

That's where a larger photosite for each pixel can come in handy (the larger surface area for each pixel can capture more light, generating a stronger signal for equivalent ISO sensivity compared to a sensor using smaller photosites). As a result, less amplifcation is needed, resulting in lower noise for equivalent ISO speeds.

That's why most DSLR models can use much higher ISO speeds compared to non-DSLR models. Their sensors are larger. Does that mean they capture more detail? Not necessarily.

There are a lot of factors involved (lens quality, lighting, etc.). Sure, if light is low, the DSLR is going to be able to shoot at ISO speeds that would cause degradation of detail from noise with most non-DSLR models.

But, in better lighting (especially if the image doesn't have too much dynamic range), a non-DSLR with a much smaller sensor can compete just fine for most purposes.

Even if the area of the sensor did increace that much, the lens would also have to capture more detail to maintain quality cropped.
Again, it's not really the size that controls how much detail you're capturing in many conditions (providing noise doesn't start creeping in). But, I'd agree with you on the lens being important. At some point, even if you have loads of photosites, the sensor is going to start outresolving many lenses.

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