Higher pixel density => more noise?

[niels123]

A video of Tony Northrup about noise vs. sensor size vs. pixel density: https://www.youtube.com/watch?v=_KYvp8PrCFc

One of the messages is that the total amount of light captured is determined by the sensor size, not the pixel size and that scaling down a high-megapixel photo to compare with a different sensor with less megapixels is the way to go. So yes, higher pixel density gives more noise per pixel, but scaling down also "scales down" noise.

DxO found similar noise levels between 5D3 and 5Ds when both compared at 22 megapixels.

If noise is ignored, is the amount of detail captured on a 22 megapixel sensor exactly the same as on a 50 megapixel sensor when the image is scaled down to 22 megapixels in postprocessing? If so, why would you then not just buy only a 50 megapixel camera and just scale down all high-iso stuff to end up with 5D3-like images? (Ignoring capture speed, AF-accuracy etc.)?

I'd like to have your toughts about this.

Niels

 

[Don Haines]

Things are never that simple.....

How much of the light entering the sensor is blocked by the electronics? This depends on the design of the sensor, the fineness of the lithography, and the number of pixels....

an approximation that is good at one end of the scale may not be good at the other end of the scale.... At low ISO you can "convert" to a standard number of pixels, but at high ISO, even though you can convert, the larger pixels can give you enough shutter speed to get the shot, so people start to change shutter speed and ISO values differently on a camera with big pixels than they do on a camera with small pixels and the comparison falls apart....

 

[niels123]

Things are never that simple.....

How much of the light entering the sensor is blocked by the electronics? This depends on the design of the sensor, the fineness of the lithography, and the number of pixels....

an approximation that is good at one end of the scale may not be good at the other end of the scale.... At low ISO you can "convert" to a standard number of pixels, but at high ISO, even though you can convert, the larger pixels can give you enough shutter speed to get the shot, so people start to change shutter speed and ISO values differently on a camera with big pixels than they do on a camera with small pixels and the comparison falls apart....

Because with more pixels you will quicker see motion blur? What would happen then if you take two identical shots with the 5D3 and the 5Ds. Then at pixel size (real 1:1) you do see motion blur only in the 5Ds shot. If you then "convert" the 5Ds image to 22 megapixel, do you then "lose" the motion bur?

 

[Mt Spokane Photography]

There is more noise per pixel as pixels get smaller, so looking at a image at 1:1, noise becomes visible. But when printing, or viewing at normal screen sizes, the noise pretty much disappears unless you crank the ISO up.

Still, if you want less noise, with the same generation of sensor technology, larger pixels will have less noise. That's why the Sony 12 MP A7S is among the best for low noise at high ISO settings. There is a trade off, but it does not affect most of us. The heavier Bayer Filters on the 5Ds series reduce the amount of light reaching the sensor, and severely impact high noise performance. They are there to improve color and skin tones for portrait photography. You can use the camera any way you want, but have to live within the limitations.

 

[Don Haines]

Things are never that simple.....

How much of the light entering the sensor is blocked by the electronics? This depends on the design of the sensor, the fineness of the lithography, and the number of pixels....

an approximation that is good at one end of the scale may not be good at the other end of the scale.... At low ISO you can "convert" to a standard number of pixels, but at high ISO, even though you can convert, the larger pixels can give you enough shutter speed to get the shot, so people start to change shutter speed and ISO values differently on a camera with big pixels than they do on a camera with small pixels and the comparison falls apart....

Because with more pixels you will quicker see motion blur? What would happen then if you take two identical shots with the 5D3 and the 5Ds. Then at pixel size (real 1:1) you do see motion blur only in the 5Ds shot. If you then "convert" the 5Ds image to 22 megapixel, do you then "lose" the motion bur?

Since the 5d3 behaves better at high ISO, you are more likely to shoot at a higher ISO to avoid the motion blur, but at the expense of worse noise....

but even then, the noise is not easy to figure out.... yes, at the same ISO the larger pixels will have less noise, but the downsampling of the image with more of the smaller pixels will reduce the apparent noise on that image.... and how far you crank up the ISO on the larger pixels makes it's noise greater... no easy answers here....

for example.... say that at 1/500 of a second you would get 4 pixels of blur on a 5D3, where at the same ISO on a 5Ds you would get 6 pixels of motion blur.... once you downsize the 5Ds image to the size of the 5D3 image, you get 4 pixels of motion blur on the downsized 5Ds image.... BUT, since the 5D3 works belter at high ISO, the user is likely to shoot at higher ISO and the shutter becomes (for example) 1/1000 of a second and ends up with 2 pixels of motion blur.... so the user ends up with a less blurred picture that MAY have greater noise....