The screenshots taken on the iPhone are never blurry. Rather they are saved as a lossless file format i.e. .PNG. If you see a vague screenshot on an iPhone, it means that you took a screenshot of the image that was originally blurred. The .PNG file may also convert into a different format if forwarded to anyone, and this could create blurry images. Or you may need sto check the picture with your reading glasses on as well.