Here is my understanding. This can be a quagmire and could open a can of worms...we shall see when the first snark hits. This has been a road hoed many times on this site.

Here is my basic understanding:

First, there is science about what is actually needed. There are charts avail which highlight the image size vs. viewing distance of the photograph. There is also the pixels per inch that are printed! (Take a look at this article: https://fstoppers.com/originals/how-many-megapixels-do-you-need-print-billboard-220239). The human eye can only see so much resolution. According to fstoppers that equation is: 2/(viewing distance in inches x 0.000291) giving one pixels per inch resolution. According to this article, at 2500 yards, one pixel printed out could be 16 inches square! And still look smooth, good resolution to the human eye. The same calculation goes for photos in your house.

That is why there are billboards made with smart phone photos because the photo is viewed from 2500 feet, 25 inches. Get up close and you would see large dots of ink. At the Reagan Library there is a portrait of Reagan done in jelly beans...far away it looks like a portrait until the viewer gets a little closer. Same with mosaics. So viewing distance is important. For instance you would not put a 24x36 inch photo in a small hallway...as people passed, they would see the pixilation, dots, on the shot because they would be viewing it from about 1 foot away. Smaller prints viewed closer up need greater resolution...not less. So it is counter intuitive, but bigger prints actually do not need higher resolution when viewed from proper distances. This is why ardent pixel peepers are never going to be satisfied.

Second, higher resolution is helpful for those who need to crop a lot..it is a fact. I use m43 gear, so cropping is a challenge. How many times on this site have we seen people asking for help on their grainy pics only to learn that it was a crop of a crop of a crop?

Third...AI is somewhat changing all this...in my case, using a lower resolution sensor, I can upsize a shot using LR's enhance feature, and do pretty decent cropping. Is it in the 40mp range of quality? No, but good enough for me.

Fourth...IMO, there are graphics and lens quality issues as well. Nothing beats high quality lenses...one can have high mp and yet if a low quality lens is hung on the camera, all is lost.

To me, MP are like horsepower in a car. It makes for great press, but there is a lot more to a car than horsepower. I once read where a car engineer was talking about some Mustang they developed with less HP than the Shelbys...he said the hp had to match all the components, such as suspension, tires, transmission, etc...and the lower HP engine actually made for a better, if not faster (due to being able to control, shift, etc.) car. The entire system has to be configured to work well together.

This is a long Sunday morning way of saying, "I think I am right but let's see what others day...BurkePhoto?)

Viewing distance be damned Working in a Art Gallery of Large Format printing up to and including 7 feet tall and close to 10 feet wide . When people walked it the gallery they walked up to it and put their nose 1 foot from it amazed that they could see every stone as far as they could see into the image ... Why because it was shot on a 645D at the time 40 megapixels from multiple stitched images from a Gigapan . The more the pixels the more detail was captured . Not one person that came into the gallery stood more than 3 feet away on any image . So many stood so close to the large print of the grand canyon they would lose their balance we had to put up a rope barrier to keep them from standing so close . This work was not mine but My boss . It just the nature of the people to get close . The following image was shot at the Gallery .That is my boss in the photo .This from a cheap cell phone and does not do the image justice It is also from Facebook .

What a stunning image! I'm surprised you refer to yourself as an amateur photographer. It's hard to believe that you aren't above that stage. Congratulation on a very beautiful image. If it was mine I would have it enlarged enough to cover a complete wall.

This will probably open a giant can of worms so I apologize in advance. How many MP’s are really necessary for the average non-professional person taking pictures? By “average person” I mean someone posting on the internet, looking a photos on a computer or iPad, or cell phone. Maybe blowing up to 16x20 on a rare occasion. There are some really great deals on older cameras with 16 mp as an example. They don’t have all the bells and whistles of the latest and greatest but really, does everyone need 26,30,40 even 40mp’s? Just curious what your knowledgeable folks think. I know everyone has different needs but what do you consider adequate?