Just because you are as honest and genuine as the day is long doesn’t mean to say that you will appear that way in photographs. Some of the most honest people that I know are so shy that their uncertainties come over very strongly in their appearance. As a result they look positively shifty in photographs. Similarly we all know people that appear honest on film that we wouldn’t trust with our loose change.
So what is the secret of looking open and trustworthy on camera? Practice. Practise having your photograph taken in an interactive photo-shoot. Learn how to engage the camera with your eyes, cultivate a genial smile, and let those lines of expression demonstrate concern.
But remember any solution is specific to you. For example a half smile works for some while for others it becomes a leer. A full smile is very attractive on some people but on others it resembles a staged grimace.
Work on your facial image and body language through a proven effective interactive process and have fun doing it.