writes:

Generally, any flight that includes compensation to the pilot in any
form as a result of having made the flight requires a commercial.

If he is compensated for the flight. But if he is working on his own as a
photographer, that doesn't count. The aircraft is a tool of his trade, he is
not flying for hire.

But aerial photography where the photographs are for sale is clearly
a flight made for the sole purpose of making money and the flight is
essential to the photography so it requires a commercial.

The flight is not essential to the photography, since he could hire someone
else to do the flying.