Too Many Megapixels

[AndyfromVA]

I just read the Pentax P70 review. It's beginning to sound like a broken record - nice looking camera, lots of features, but noisy at low ISO's and soft pictures caused by noise reduction.

We all know why this is happening. Too many megapixels in too small a sensor. Personally, I think any camera with 12 megapixels and a 1/2.3 inch sensor must be presumed to be flawed and not worth purchasing.

[Hawgwild]

I agree. My old Nikon D50 at 6 mp had great low light performance at 1600 iso, with little noise. My Sony A300 at just 10 mp has more noise at 800 than the D50 did at 1600, according to the exif on pics I compared. This megapixel insanity needs to slow down a little. Unless you are going to do some heavy cropping, you don't need much more than 6-8 mp, especially if your'e only ever going to print at 4x6 or 5x7. Just my opinion...

[TCav]

It seems only Canon has an effective way of dealing with noise: stop it before it starts. That requires technology at the photoreceptor level. While some methods are certainly better than others, any attempt to reduce noise after the fact will reduce detail.

[peripatetic]

This is one of the most persistent myths on the internet.

In fact if you take a 12Mp sensor and down-rez the image it will give the same amount of noise as a 6Mp sensor with the same level of underlying technology.

It just seems noisier because if you view a 6Mp image at 100% you should be viewing the 12Mp at a lower percentage, not 100% in order to compare noise.

Make a standard 8x10 print from both cameras, if the sensor has the same underlying technology then the noise visible in the print will be identical. So in fact you lose nothing by having the extra pixels, and you gain the ability to capture extra detail if the light is good enough.

If you think this is wrong then think carefully about why the sensor analysis at DXOLabs doesn't take any specific notice of the resolution of the sensor when analyzing its performance.

http://www.dxomark.com/

DXO has quite a good little section on Noise, recommended reading for sure.

[rjseeney]

Hawgwild wrote:

I agree. My old Nikon D50 at 6 mp had great low light performance at 1600 iso, with little noise. My Sony A300 at just 10 mp has more noise at 800 than the D50 did at 1600, according to the exif on pics I compared. This megapixel insanity needs to slow down a little. Unless you are going to do some heavy cropping, you don't need much more than 6-8 mp, especially if your'e only ever going to print at 4x6 or 5x7. Just my opinion...

The D50 was very good at handling noise. However my D80 was better at 1600 with more pixels and my d300 is better at 3200 if exposed correctly with twice the pixels.. I have an Olympus E-510 that is also as good as the D50 with more pixels AND a smaller sensor. Each successive Nikon camera has gotten better at noise handling with more pixels. There is no situation I can think of where I would choose the D50 over any of the current crop of DSLR's.

[TCav]

Noise happens at the pixel level.

Downsampling mutes noise (no pun intended.) The more downsampling, the less objectionable the noise. A 6MP image displayed on a 1280x1024 screen will show more objectionable noise than a 12MP image with the sameproportion of noisy pixelson the same screen. A 100% crop of a 6MP image will show more objectionable noise than a 50% crop of a 12MP image with the sameproportion of noisy pixels.

Upsampling amplifies noise. The more upsampling, the more objectionable the noise. A 6MP image printedat 8x10 will show more objectionable noise than a 12MP image with the sameproportion of noisy pixels.

BUT, the 12MP image won't contain the sameproportion of noisy pixels as the 6MP image. Because of the higher pixel density, it will contain more noisy pixels, proportionally (all other things being equal.) The noise will be more muted as a result of downsampling, and less amplified as a result of upsampling, but higher pixel density is not the answer. If it were, then images fromP&S digicams would have less objectional noise than images from dLSRs (all other things being equal.)

The problem with this discussion is that all other things are not equal.

[peripatetic]

DXO labs disagree.

http://dxomark.com/index.php/eng/Insights/More-pixels-offsets-noise!

http://dxomark.com/index.php/eng/Ins...tion-over-time

Increased resolution has more than compensated for the increase in noise from smaller pixels.

It's fairly obvious and has been for a long time. The only way to reduce the noise in a picture (at a given level of technology) is to capture more light i.e. use a bigger sensor.

[TCav]

peripatetic wrote:

DXO labs disagree.

I'm not disagreeing with DXO, and they're not disagreeing with me.

A lot of things have changed since the mainstream dLSR had a 6MP image sensor. If we still made APS-C 6MP image sensors (the Nikon D40 notwithstanding,) they would have less noise than they did 3 years ago. But we don't (the Nikon D40 notwithstanding.) We make APS-C 12MP image sensors instead, and on a pixel for pixel basis, the 12MP image sensors are noisier than the 6MP image sensors were 3 years ago. But the greater resolution hides the noise (through upsampling and downsampling.)

[Hawgwild]

Are ya gettin' all this, Andy? LOL

[AndyfromVA]

Hawgwild wrote:

Are ya gettin' all this, Andy? LOL

I'm gettin' it all right. But I can't say I really understand it.