If it is still letter form even though it is small that is just fine. If it gets that small that the computer cannot draw that they may as well be morse code, you can test how well you mind can decipher those dots and dashes.
Using the imaginary X technique you will find that the font can be PhotoRead well even though it is small enough that you would pull it within 3 inches of your face.
Work within your comfort zone.
Alex