The dependence of the zoom on the matrix and focal length - how to understand?

Question

Photo

What is the relationship between the matrix and the focal length if we crop the original image? The task is to get the maximum approximation of the object with the minimum possible loss of quality.
For example, there is a Nikon P1000 with a 16Mp 1/2.3 3000mm matrix and some other camera with a full frame 24Mp and a 210mm lens.
In what case can you get the closest possible object with maximum quality, taking into account the subsequent crop of the frame? Or, on the other hand, how many megapixels should a full frame matrix have, what focal lens and by what percentage should the frame be cropped in order to get an identical approximation as on the Nikon P1000 when using 3000mm?

Answer 1

Cropped lenses are brought to normal focal length. That is, for a full frame, the same 3000 mm are needed.
There are such banks, but they are very, very expensive.
However, perhaps I will please you with a matrix on this device of very low sensitivity and at such ranges there will be a "shake", so take your usual zoom and shoot at close range, or alternatively put magnifying rings on the lens.
PS What prevents you from taking a series of pictures and comparing? For example, go out to the balcony and take some pictures of cars on the road

Answer 2

To begin with, let's bring the Matrices and lenses (3000, as I understand it in 35mm equiv) to a common denominator - crop 24MP to 16MP -> 24/16=1.5 and increase the lens by the same amount -> 210*1.5=315
Now formally equating the matrices, we have 315mm on a full frame camera versus 3000 on a small one. Now we see that in order to get a similar approximation from a full frame by further cropping on the same lens, you need to have a matrix almost ten times denser, i.e. 240MP
Well, I think you know that large lenses (with a large spot like 35mm) simply do not make for such a pixel density, they do not draw as many details.