04-10-2009, 06:05 AM
space-time,
It does look like it could be be back focused just slightly. That lens is known to be rather soft wide open but it looks like it might be focused at the 2mm line.
But - are you set up properly for this test? You should have the camera at a 45º angle from the test chart and it doesn't look like you're lined up properly. The test should be done with the lens wide open by the way.
I used the chart here when I tested my K10D:
http://pentaxdslrs.blogspot.com/2008/06/...entax.html
That site gives a lot of useful instructions and the chart itself presents a 45º angle when you have it folded up so you can rig the test so the camera is on a level surface. I used the method there to adjust the focus on my K10D (you have to have a certain firmware version and then get the camera into a "debug" mode.) I don't know if that's possible for a user to do with the istD. By the way, the K20D is user-adjustable and will remember settings for a number of different lenses.
I also rigged an outdoor test using a ladder and beer bottles. I laid the ladder on the ground and put a bottle at each rung and did a bunch of shots focusing on one bottle or another. It was very helpful and a bit more "real worldly" than shooting a focus chart.
It does look like it could be be back focused just slightly. That lens is known to be rather soft wide open but it looks like it might be focused at the 2mm line.
But - are you set up properly for this test? You should have the camera at a 45º angle from the test chart and it doesn't look like you're lined up properly. The test should be done with the lens wide open by the way.
I used the chart here when I tested my K10D:
http://pentaxdslrs.blogspot.com/2008/06/...entax.html
That site gives a lot of useful instructions and the chart itself presents a 45º angle when you have it folded up so you can rig the test so the camera is on a level surface. I used the method there to adjust the focus on my K10D (you have to have a certain firmware version and then get the camera into a "debug" mode.) I don't know if that's possible for a user to do with the istD. By the way, the K20D is user-adjustable and will remember settings for a number of different lenses.
I also rigged an outdoor test using a ladder and beer bottles. I laid the ladder on the ground and put a bottle at each rung and did a bunch of shots focusing on one bottle or another. It was very helpful and a bit more "real worldly" than shooting a focus chart.