01-12-2011, 09:50 PM
OK -- I made a better test with the [url="http://www.peleng8.com/how-to-detect-back-focus.html"]peleng8[/url] pattern:
Here's the result for f=60 mm, where the front focus is most significant. The image shows 6 different images. The focus field lies well on the checkerboard pattern which is perpendicular to the optical axis.
The scale appears to be sharp somewhere between 0 and 1, so the focus is wrong by about 0.5 which is about half of the the depth of focus (DOF) (I assume the lens to have no field curvature).
Again my question: is this significant front focus or am I too picky?
![[Image: f60_6s.png]](http://www.zellner.org/EF24-105/f60_6s.png)
- The front focus is almost not visible at f=24mm
- front focus is biggest somewhere @ f=60mm
- front focus is slightly visible @ f=105mm
Here's the result for f=60 mm, where the front focus is most significant. The image shows 6 different images. The focus field lies well on the checkerboard pattern which is perpendicular to the optical axis.
The scale appears to be sharp somewhere between 0 and 1, so the focus is wrong by about 0.5 which is about half of the the depth of focus (DOF) (I assume the lens to have no field curvature).
Again my question: is this significant front focus or am I too picky?