How much different will 0.5ml lip filler make to my lips? (photos)

This will provide you with subtle improvement. It will take 1-2 weeks for final results with lip fillers. Hope this helps.

Your lips are full to get them fuller 0.5cc is a lot. You can add to your vermillion border for definition or plump your lower lip a tad. I would say that would be enough for your lips and face. Hope this helps. JB

Hannah.   All of your preliminary information and research is correct. You have a pretty face and full lips and may not need more than .5 mL of lip filler like Juvederm ultra plus. It is a reasonable plan to have .5 mL placed in your lip by an experienced Injector, preferably a board-certified plastic surgeon or dermatologist. If you desire to be somewhat fuller, more material can be added. Better to be conservative in your case. Best of luck.

I would already be cautious of the injector selling lip filler by the cc. Lip filler is placed to achieve the result a syringe. When filler is sold by a half syringe, the injector is splitting the syringe which was made just for you. I never sell filler this way because patients will always be disappointed. 

It’s hard to evaluate your lips looking at the photo you sent, but based on what is available I think 0.5 might be enough to give you a very subtle change in the volume and shape of your lips. 

Hi
0.5cc can make a significant difference but the type of filler will also influence the effect.  Filling your lips with Volbella will be different than filling with Juvederm. 
That discussion will be important to understand what is being injected to meet your expectations 
Good luck