10-23-2011, 08:29 AM
hmmm, this suggestion may not be the correct way to do a check but it seems to work ok for me -
i have a fine even pile carpet - i point the camera on tripod at it at about a 45 degree angle or less - i place a large enough white card on the carpet so that the camera can't find focus with the focus cross point pointing at the centre of the card, but so that you can see carpet on both sides - i then place a black line on the white card, the camera then must focus on that line and, looking to either side, i note if the carpet is in focus in line with that or behind or in front of it, then it should be easy to make a correction - this didn't cost me anything, and seems to work well enough - but you might be lucky to pick it at 12mm, although you should still see the spread - and i suppose it might rely on good lens centering - but you've done that -
if you find this works check at 12 & 24 - if it's not the same either end, bummer - and sorry but i can't tell accurately from your shots -
and, having said all the above, i'm generally manually focusing at 16mm (the max wide on my not-nikon gear) and i wish the corners were better, but i accepted the second copy i tried of my lens from the shop back when i was young and innocent <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/sad.gif' class='bbc_emoticon' alt='
' />
i have a fine even pile carpet - i point the camera on tripod at it at about a 45 degree angle or less - i place a large enough white card on the carpet so that the camera can't find focus with the focus cross point pointing at the centre of the card, but so that you can see carpet on both sides - i then place a black line on the white card, the camera then must focus on that line and, looking to either side, i note if the carpet is in focus in line with that or behind or in front of it, then it should be easy to make a correction - this didn't cost me anything, and seems to work well enough - but you might be lucky to pick it at 12mm, although you should still see the spread - and i suppose it might rely on good lens centering - but you've done that -
if you find this works check at 12 & 24 - if it's not the same either end, bummer - and sorry but i can't tell accurately from your shots -
and, having said all the above, i'm generally manually focusing at 16mm (the max wide on my not-nikon gear) and i wish the corners were better, but i accepted the second copy i tried of my lens from the shop back when i was young and innocent <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/sad.gif' class='bbc_emoticon' alt='
' />