To use the chart you set it up at 45 degrees to the axis of the lens as shown below. In this configuration (at 45 degrees) the 1, 2 and 3cm marks are correct. They are actually spaced at 1.41, 2.82 and 4.23cm from the focus line, but when viewed at 45 degrees these distances are modified by the Cosine of the viewing angle (Cos 45 = 0.707).
Using the alternative test the results look similar in fact I would say there was slightly more in focus at the front than the back.
All I can put it down to is operator error ?
But its strange I get the same effect on every image and the area that I am focussing on - body - is still not great and at F11 it should have been spot on.
Well, the images certainly seem to be back focused even though the test belies that.
Maybe the image sensor is displaced to one side and you're not focused where you think you are. I'm assuming you were using the centre focus sensor.
Yes I was using the center focus sensor and I was focusing on the body area behind the eye on 3 out of the four above. But that is a good point: how big is the focus area - how accurate is it with the spot and box on the display with the sensor was there enough contrast on that area.
AF point on one of the images:
Perhaps I should have used the wings as the focus point which looking back on it I did on some of the first photos I took. The first image I posted looks a lot sharper than any of my latest ones.
How big is the focus area? I don't know I don't have (never did) a Canon.
If you tape a strip of paper to a window, you can slowly pan the camera towards the edge of it until it decides to acquire focus. That will give you an idea of where the sensor actually is in relation to the centre markings.
Last edited by Peekayoh; 07-23-2010 at 11:57 AM.