Photo aspects aside - as they have been covered, I'm pretty sure it's a trumpet fish. The photo clearly shows a number of characteristics that identify it as such. It has a chin barbel, rows of fine scales and a laterally-compressed mouth. Also, the eye is comparatively smaller (eye diameter as a % of S.L.) and less oval in shape. Cornet fish, on the other hand, lack a chin barbel and scales - rather, they are either scale-less or have rows of hard plates in the skin, and the mouth is somewhat dorso-ventrally compressed. The eye of a cornet fish is comparatively larger and much more oval in shape when compared to a trumpet fish.
In terms of the photo - either is challenging to get an engaging shot of! I'd echo the comments on exposure and focus - nice job!