What defines "low" resolution?
"Low resolution" is a relative term. Compared to a high-resolution image, low-resolution images have fewer pixels, higher compression, or both. They sacrifice quality of the image for a smaller file size.
Low-resolution rasterized images, such as photographs, may appear blurry or indistinct. You can see this blurriness in our example photograph, pictured on the right, in the detail comparison.
Vector graphics, on the other hand, are resolution-independent. When an image is rasterized (converted to pixels), the vector image can be scaled to high or low resolution as needed. If they are rasterized to a low-resolution image, their artifacts, such as jaggies, may be more pronounced.
If "low resolution" is used alone, where "resolution" is a noun, and "low" is an adjective, it should not be hyphenated. For instance, "That image was printed at low resolution."
If "low-resolution" is used as a compound adjective, in which both words describe another noun, it should be hyphenated. For instance, "That is a low-resolution image."