Originally posted by Mapleleaf-Mick Can anyone enlighten me on the difference between pixel count I. E. 40 mega pixel sensor and the pixel density of a sensor. It would appear from my reading that you can get a higher pixel density from a lower pixel sensor which in theory should give you a better picture.
Not all semi conductor photo sites aka Pixels ( Picture Elements) are created equal. An often used analogy is water buckets.
Large buckets capture more rain ( photons) than small ones in the same amount of time. As buckets get smaller, the ratio of orderly, well behaved photons vs ill behaved juvenile delinquent photons (noise) increases and their useful sensitivity becomes increasingly less. And this happens before the digital electronics which amplify the captured light energy, another source of noise. Although the electronics are getting very, very good and nearly noise free.
If the bucket is filled to 100% of capacity, it's an ideal exposure value. Sensor designers call this full well capacity or how many photons fill it up, an optimum signal to noise ratio.
If the bucket is barely filled, the image is underexposed. S/N ratio is much less.
So fill the room with buckets. If the room is APS-C sized, the only way to get 24 million buckets in the room is to use smaller buckets, placed closer together ( pixel size & pitch) vs 16 million buckets. You can look up pixel size & pitch for most digital sensors.
It is the primary reason cell phones are so limited is sensitivity. While sensor technology gets better and better, there are limits due to the wavelength(s) of light. A single photon can spill into multiple photo sites.
In practical terms, my 16 MP K5IIs bodies serve me very well for the low light, high shutter speed challenges of dance performances. My 24 MP K3Ii gives me very welcome higher resolution in studio and portrait sessions. If I end up with a K-1, I'll use APS-C modes for most performance images as file size and volume of images is a significant consideration. I would use FF mode when it made sense like something intended for large promotional images. Haven't shot a K-1 but I have rented the 645z and because of the larger pixels & pitch, the dynamic range is just wonderful.
I'm in the process of finishing a print order for a client who ironically is an Adobe rep. (did his headshot). He sent me some iPhone 6 JPEGs he made on vacation which I edited and enlarged to 12x18. They're going on metal ( aluminum) and I ran full size glossy proofs. He had lots of light and the images look great. So it all depends on the application.