Resolution, megapixels, sensor size, and line pairs per millimetre.

I realise it's the photographer that makes the image not the camera. This post is about the tools they choose to use. 

There's been, and perhaps there always will be talk recently about camera phones making cameras obsolete. For holidays snaps etc. this is perhaps already true.

How do you measure resolution with a digital camera?

According to what I've read the I Phone 11Pro has a 12 megapixel camera, with a 1/2.3 inch type sensor. It is and I quote, "typical for smartphones and superzoom point-and-shoot cameras". The sensor size is 6.17mm x 4.5mm.

My elderly Nikon D300 is also a 12 megapixel camera, but it has a Nikon DX sensor which measures 23.6mm x 15.8mm. That's considerably bigger. In fact its nearly the same size as the negative from an old 35mm half frame camera.

Which gives the better resolution, the one with the pixels concentrated in a smaller space,or the one with the pixels more spread out? As I understand it giving the pixels more room means they can be larger,and therefore more sensitive. This means less noise generated at low light levels. It should be said that the sensor in the I Phone should be more technologically advanced than the one in my D300.

Back in the day when all photographers used film we measured resolution in line pairs per millimetre. A camera / lens / film combination was used to photograph a chart with increasing line pairs on it. Then the negative would be examined to determine the maximum line pairs were visible.

The problem here is there are so many variables. Using Ilford Pan F (ISO 50) should give better results than using HP5 (ISO400). Then there's the lens or even the aperture set on the lens. The same must be true of digital cameras.

So how do you work out the resolution of your camera. It's not just the number of megapixels, sensor size is important, as is sensor age. I suspect the ISO setting has something to do with it as well.

Any thoughts? Are you about to give up your DSLR, in favour of a high end phone camera? Have you already done so?