I think by default it's set to 4.0, and if you increase it it gives the image a "fry" effect?
The more it is the more closely it follows the prompt. However, after a certain value it becomes random. Think of it like weights for the prompt. Increasing guidance makes generation follow more closely to the prompt
Is there a way to calculate the optimum Guidance scale ?
@AnshCharak It heavily depends on your need. The best way to go about it is to create a grid of varying Guidance scale samples with 5 to image per row. You can then figure out how it is. My general values are between 7.5 to 12.5. These give desired results more often than other ranges. But it is upto you frankly. There is no optimum Guidance Scale.