Sensor Size?

Question

About 2 wks ago I thought Dr. Sam mentioned a camera that had a larger sensor size than another would have a better image quality. I myself go by rating organizations.
A kodak C433 4 megapixels has sensor size 1/2.5",type ccd
A canon SD900 10 megapixels has sensor size 1/1.8(7.18x5.32) type ccd
I understand MP at 4 verses10, but where does size of sensor come into play?

Answer 1

Hi VintageMusic,

Here's a great page on pixels and sensor size. Go about 1/3 of the way down and read the text under the chart showing different sensor sizes.

http://photo.net/equipment/digital/basics/

There are more specific details here:

http://photo.net/equipment/digital/sensorsize/

As far as pure pixel density, the 4 MP Kodak has fewer pixels per square millimeter than the 10 MP Canon. This is where rating organizations can be most helpful. If it was solely dependent on pixel density, a 3-4 MP camera might have better image quality. There are other factors that go into sensor design, though. The software that deals with the light gathered by the sensor makes a huge difference. The lens that you put in front of the sensor is very important. There is one camera out there that is using excellent lenses in front of crappy sensors, so reading reviews is essential if you want to know which camera is really best. I agree.

In an "all other things being equal" analysis, though, a general rule is that the bigger sensor will get the better image with less noise. This is why pretty much ANY dSLR out there will be better than virtually ANY point and shoot out there. The sensor in a dSLR is from 343 mm(sq) for most Canon's to 366 mm(sq) for most Nikon's. I'm not saying that the Nikon (Sony) sensor is better by any means, but they are both in a different world from the 38 mm(sq) of a 1/1.8" sensor or the 20 mm(sq) of a 1/2.5" sensor.

In fact, look at the difference in image quality at low light for a Nikon D80 and Sony Alpha-100. Supposedly this is the SAME SENSOR, but the D80 just kills the A-100 in low light image quality. Nikon is doing something different with the sensor then Sony is.

Look at the difference between the Nikon D80 and Sony A-100 at ISO 800 and ISO 1600 on this page:

http://www.dpreview.com/reviews/nikond80/page27.asp

For that matter, compare the two Canon's shown on the same page. They both have the same size sensor. In fact, is it the same sensor??? I'd say that the 10 MP 400D tames the noise a bit better than the 8 MP 350D, wouldn't you? Logic would say that the lower pixel density in the 8 MP 350D would lead to lower noise, but it's all in the noise reduction algorithm used by the camera manufacturer.

Answer 2

I didn't see Dr. Sam's answer, but sensor size and megapixels pretty much go hand-in-hand, on professional cameras, at least.

Maybe what Dr. Sam was talking about was the actual size of the individual pixels. A camera with larger pixels will, generally speaking, will have less 'noise' in the pictures (at high ISOs).