The pixels bought by SLR cameras are not good. Can you adjust the definition with an external lens?

The external lens is equivalent to a telephoto lens that acts as a telescope, which can reduce the foreground, but it will not improve the resolution and pixels, so it cannot improve the definition.

The lens material is low-end, and the accuracy is not high, which reduces the imaging quality. Moreover, the greater the magnification, the less light passes, the darker the image and the more noise, so instead of improving the definition, it will reduce the definition.