The DSC-S85 started its public life (at least here on dpreview) as a rumour back on the in mid-March this year. This rumour originated with an Australia website and was soon given a little more viability by Sony Microelectronics announcement of the ICX406 4.1 megapixel CCD sensor. This CCD is the same 1/1.8" size as the previous 3.34 megapixel used on a large number of today's 3 megapixel consumer digital cameras, thus turning a 3 megapixel into a 4 megapixel seemed like a relatively trivial task.
The DSC-S85 enters the market as the first 4 megapixel consumer level digital camera (of course we've all seen Olympus's E-10), and we're honoured to be able to bring you this review at the beginning of what seems to be the next era in resolution.
Four.one, three.three, three.one or three.eight?
Here's how the specifications of the ICX406 CCD stack up against the 3 megapixel ICX252. Note that the AQ / AK suffix simply denote the type of colour filter array used on the sensor.
|Product name||Colour Filter Array||Pixel count||Effective resolution||Image
|Cell size||Effective active pixel area size|
|ICX252AQ||GRGB||3.3 megapixel||2088 x 1550||1/1.8"||3.45 µm||7.20 mm x 5.35 mm|
|ICX252AK||CYGM||3.3 megapixel||2088 x 1550||1/1.8"||3.45 µm||7.20 mm x 5.35 mm|
|ICX406AQ||GRGB||4.1 megapixel||2312 x 1720||1/1.8"||3.12 µm||7.20 mm x 5.35 mm|
As you can see the active pixel area is the same (as we'd expect) and of course because the ICX406 is packing in more pixels the cell size (pixel size) is now down to a 3.12 x 3.12 µm.
Of course, you don't get the whole 2312 x 1720. Some of the horizontal and vertical pixels are used to measure the "black point" of the CCD, the level from which black is measured. From the 4.1 megapixel CCD the camera uses 3.8 megapixels (2272 x 1704). Here's a diagram representing the increase in pixel count from 3.1 to 3.8 megapixels:
Doesn't look like a huge amount, does it? Well, here are a few ways of thinking about it:
- The image is 224 pixels wider and 168 pixels taller
- The image has 725,760 more pixels
- For every 9 x 9 group of pixels on an S75 image the S85 has 10 x 10 pixels (approx.)
- Prints at 150 dpi would cover an extra 1.5 in horizontally and 1.1 in vertically
Here are other things to consider about this new 4.1 megapixel sensor:
- The smaller the cell size the less sensitive the sensor (thus more amplification of the analog signal would be required to produce the same required light sensitivity)
- This sensor is a year advanced in development from the 3.3 megapixel sensor
- This sensor requires the lens to produce 320 lines/mm to produce maximum resolution
- Bigger sensor = more data = higher processing requirements
- Bigger images = larger files
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