Why is an error thrown when setting the width and height attributes on an ImageField model field?

Question

Django

In the model, I specify the following field:

image = models.ImageField(upload_to='photos', height_field=60, width_field=60, max_length=100)

when I try to create an object in the admin panel, I get the following error:
TypeError at /admin/gallery/photo/
getattr(): attribute name must be string

Answer 1

Because these attributes do not set the width and height of the picture. They set the names of the fields in which djanga will write the actual width and height of the loaded image. Something like that:

class MyModel(models.Model):
    img_width = models.PositiveIntegerField(null=True)
    img_height = models.PositiveIntegerField(null=True)
    image = models.ImageField(upload_to='photos', height_field='img_height', width_field='img_width', max_length=100)

Answer 2

Why is it even needed then?