I recently purchased a graduated ND filter for sunrise and sunset photography - i.e. to hold back bright highlights. My K-r's internal highlight correction feature is fine, but has its own shortcomings. The filter in question is 0.6, or 2 stops. But here's my question:
isn't that 2 stops achieved only on full frame? The K-r sensor is APS-C, so doesn't that make the filter's effect only about 1 stop?
Here is a visual comparison of FF and APS-C sensor size. If we place an imaginary horizon through the center, the upper part of the filter (where it is most dense) isn't seen by the APS-C sensor.
This tells me that if I want 2 stops with a graduated ND filter, I have to buy a 1.2, or a even better, a 1.5.
Is my assessment correct?