For the last 13 years we have used exclusively premium grain granite for laser engraving. We want only the highest possible image quality for our customers. When choosing a company for your laser photo engraving make sure to ask what type of granite they use.
Granite makes a difference when laser engraving images. By Looking at the photos above the more coarse the grain in the granite the more noise you will have in the final engraving. Not only will there be more noise in the photograph but the coarse or large grain will reduce the detail and contrast. Why would a company use a coarse grain granite over a fine grain granite? The main factor is cost and availability. Coarse grain black granite usually cost less than a premium fine grain black granite. Another factor is that premium black granite is not as readily avaiable compared to coarse grain granite, it's harder to locate.
Granite is a natural stone and will have some grain and artifacts, but choosing a premium granite that has a finer grain will improve the detail and contrast of photo engraving.