Because I post on Instagram too so I always take a couple pics with my phone, using daylight or a daylight lamp I like. I do scan some images tho… for other things. I am surprised at how well the iPhone works but it does leave grey edges often around the edges. In a black and white image you can almost completely correct this, but not in a watercolor image, and I am showing you what I mean because it is so easy to see in the BW image before I corrected it.
With exposure modifications I can nearly correct the image above, but not the image below without ruining the colors. I scanned this one eventually because I had another purpose in mind.