Vim: ignore case in "f" and "t" motion commands

I would suggest something like:

function! ForwardLookup()
    " get next key pressed
    let c = nr2char(getchar())
    let old_search_pattern = @/
    " Use of \V enables very-nonmagic pattern
    exec 'normal /\c\V' . escape(c, '\/') . nr2char(0x0d)
    let @/ = old_search_pattern
endfunction
nnoremap f :call ForwardLookup()<CR>