I know posting eyeballed drawings is against the rules, but what about vectors that a photograph (that the artist did not take) was used as a reference picture?
Is the picture truely referenced, or was it vectored over the photograph?
According to the first post, refering to the picture done from the photograph of the Sailor Moon cosplayer, no, if it is exactly like the photograph, even if you can't get certain elements to look precisely like the image.
If you're say, using the photograph for the lighting, then yes, you may use it.
If you're picture ever looks exactly like your "reference" then you're not referencing, you're copying.