We　compare　five　slope　correction　methods　developed　by　Walter　et　al.,　Montes　et　al.,　Schleppi　et　al.,　España　et　al.,　and　Gonsamo　et　al.　(referred　to　as　WAL,　MON,　SCH,　ESP,　and　GON,　respectively)　using　artificial　fisheye　pictures　simulated　by　graphics　software　and　a　lookup　table　(LUT)　retrieval　method.　The　LUT　is　built　by　simulating　the　directional　gap　fraction　as　a　function　of　leaf　area　index　(LAI)　and　average　leaf　inclination　angle　(ALIA)　using　the　Poisson　law.　LAI　and　ALIA　estimates　correspond　to　the　case　of　the　LUT　that　provides　the　lowest　root-mean-square　error　between　the　observed　gap　fractions　after　slope　correction　and　the　simulated　ones.　Three　LAI　values　(1.5,　3.5,　and　5.5),　four　ALIA　values　(26.8°,　45°,　57.5°,　and　63.2°),　and　three　slope　angles　(0°,　20°,　and　50°)　constituted　36　samples　of　random　scenes.　ESP　is　recommended　because　its　results　are　accurate　and　independent　on　the　leaf　angle　distribution　(LAD),　while　GON　only　performs　well　for　spherical　LAD.　The　three　other　methods　present　less　good　performances　with　underestimation　or　overestimation　of　LAI　and/or　ALIA　depending　on　the　LAD,　and　the　recommended　order　for　them　is　MON,　SCH,　and　WAL.　©　2004-2012　IEEE.