Effect of number of megapixels for a given sensor on image quality?

Question

So I know cramming more and more megapixels on a given sensor (cough cough the crappy nikon s50c I tried out that puts 7mp on a 1/2.5" sensor). If you just turn down the megapixels (like if i had just set it to 3mp) would it put the quality to as htough the sensor were made for those settings?

Answer 1

No, unfortunately. Instead, what it does is that the image is captured at 7MP then down-sampled to 3MP. Some of the noise may go away, but it would have been better to just have a 3MP sensor in the first place. For compact cameras, I think 4MP and 5MP sensors are about the max. Beyond that there are diminishing returns, particularly in low-light performance but also in image clarity (due to diffraction).

Answer 2

Sensor Size

Sensor size is made more confusing by the archaic way that they are described. Think of the fractions as if there were no decimals involved. 1/1 is bigger than 1/2. 1/1.7" is bigger than 1/2.5". As a general guideline, the bigger the sensor, the better the image quality.

1/2.5" is probably the most common sensor size in point and shoot digital cameras. It is about 5 mm by 4 mm, or 20 square millimeters.

1/1.8 is 7.2 mm by 5.3 mm or about 38 square millimeters.

I don't know the exact dimensions of 1/1.7", but it would be slightly larger than the 1/1.8", although mot so much larger that it would offer any real advantage in image quality.

Here's a good page to study:

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

One question that we get fairly often here is, "How do I make my subject in sharp focus with a blurry background?" The smaller the sensor, the harder it is to accomplish this. You will see an explanation (if you want details) on this page:

http://www.photo.net/learn/optics/dofdigital/

Another thing that you might notice is that the "super zoom" point and shoot cameras tend to have the 1/2.5" sensor. Since focal length is a function of image size, this is how the camera designed is able to achieve such extreme zoom power (10x - 12x is common). The smaller the sensor, the greater the "lens factor." A Canon Powershot S3-IS is said to have an "equivalent focal length" of 36 mm-to-432 mm. Considering the lens factor of 6.03x for all 1/2.5" sensors, the real focal length of this lens is about 6 mm-to-72 mm.

Here is a mini-tutorial I made myself to compare 10 MP sensors in a digital SLR (DSLR) and a point and shoot (P&S) camera. I have tried to keep everything on equal footing with no unequal cropping of the original images. Both images were taken at the equivalent of 75 mm from about 1,000 feet away. View this FULL SIZE and scroll through the image to compare the resolution at various points of the images. To me, the P&S sensor practically looks like an impressionist painting compared to the DSLR sensor. Please note also that this is the "large size" P&S sensor, as most are using the smaller 1/2.5" (5x4 mm) sensor.

http://www.flickr.com/photos/7189769@N04/476181751/

Answer 3

Nope.
It's the sensor size that's important. That's why I tell people that anything over 6mp in a compact is a waste. The small sensors don't give satisfying resolution or colors.

That's why dSLR's are so much better.

Answer 4

the sensor can handle the 7mp
they made it for 7mp