Enhance passes generated images through NovelAI Diffusion a second time to improve upon them, based on the prompt. It differs from upscaling in the way that your text prompt affects the enhancement as well, allowing you to adjust the prompt to, for example, focus the AI on any lacking aspects if needed.
Goose Tip: Enhance will continue to consider your text prompt, so you may adjust your prompt to focus on areas that you find lacking. For example, you can improve the sharpness or shift the focus of your generation by repeating aspects if the AI seemingly ignored a part of your prompt.
The Magnitude slider uses combination value combinations of Strength & Noise. You can select the Show Individual Settings Option to set the individual values yourself.
If you want full control over the way your image is going to be affected, then select Show Individual Settings. Now you can manually adjust both the Strength & Noise values as you see fit.
Setting high Strength values will change the image significantly. A low Strength affects the original generation less. A higher Noise setting may allow the AI to generate more detail.
The Enhance feature also has a setting that allows you to increase the resolution of the image as the other enhancements are applied. Not to be confused with the dedicated Upscale tool.
Goose tip: Want to just upscale an image without applying other sorts of image generation artistic influence? Better use the Upscale tool instead!