Generating the mandelbrot set - zoom, area and iteration depth

Question

I have a list of areas of interest where I would like to zoom into the Mandelbrot set. Unfortunately, I don't know the iteration depths to be used.

Question 1: Given (x_min, x_max, y_min, y_max), is there a formula providing a rule of thumb for a reasonable max iteration depth?

Question 2: Given a nice picture, is there a formula providing a rule of thumb how to adjust the max iteration depth when zooming into this picture? like new_max_iter = func(zoom, new_zoom, max_iter)

I am using the iteration number to colorize the set:

def calc_mandel(x_space, y_space, max_iter=50):
    res_arr = []
    for y in y_space:
        row = []
        for x in x_space:
            c = complex(x,y)
            z = 0
            for i in range(max_iter):
                if (z * z.conjugate()).real > 4.0:
                    row.append(i)
                    break
                else: 
                    z = z**2 + c
            else:
                row.append(0)
        res_arr.append(row)
    return res_arr

and

graph = ax.pcolormesh(x_space, y_space, res_arr, cmap='magma')