02-03-2014, 11:11 PM
It is 30m (APS-C: 60x focal length).
The magnification of the test target is identical across all focal lengths.
Technically it is possible to come closer but then you require a higher resolution test target and the error margin increases due to the more shallow depth-of-field.
We had some discussions regarding test targets based on masks used for chip manufacturing.
I think backlit targets would violate the Imatest guideline of testing dark grey targets - using backlit you increase the contrast between black and white quadrants.
The magnification of the test target is identical across all focal lengths.
Technically it is possible to come closer but then you require a higher resolution test target and the error margin increases due to the more shallow depth-of-field.
We had some discussions regarding test targets based on masks used for chip manufacturing.
I think backlit targets would violate the Imatest guideline of testing dark grey targets - using backlit you increase the contrast between black and white quadrants.