Must be a grandson or such - as too good of a picture for 1829, a daguerrotype wouldn't be so nice and that's the best they could have done. You should talk to the person who put it up and ask more questions about which Malcolm it really is. Good work finding these though and let me know what you find!
p.s. Ancestry has this photo under Hugh Finlay Malcolm, son of Finlay Malcolm and Alma Fleming.