Originally posted by Fogel70
There is some thing I don't like about the CIPA test. Blur is determined by checking A5 prints with 65-80 cm viewing distance and the stops calculated is using 1/focal length x "crop factor" shutter speed.
Using that small print with that long viewing distance will probably mask a lot of camera shake, and many experienced photographers can probably hand hold camera without image stabilization 1.5 - 2 stops below 1/focal length x "crop factor" shutter speed and not detecting any blur at that test scenario.
IMO A3 prints should have been use at that viewing distance, not A5.
Again, I believe this statement is due to misunderstanding (I for myself only glimpsed through it, but anyway...).
The blur is determined very much as described in my paper about "Understanding Image Sharpness" (cf. my blog or hp). They even "use" my formulas about how to combine static and motion blur. It is determined by digital image analysis and measured in microns. Nothing gets printed. My own determination of SR efficiency was very much like the CIPA procedure, replacing the vibration apparatus by human tremble
Using 1/equivalentFocal makes sense, it is the established rule of thumbs. At 10 mrad/s tremble (again, cf. my paper), this creates about 10/1000 focal/equivalentFocal mm or 10 microns/cropFactor blur. Or about 1/3 the max. depth of field blur. So, the rule of thumb is a compromise between visible in print from a distance and visible in pixel peeping.
A measurement of rotational blur in the standard would have been difficult. It depends on the location in the image and the current standard allows to determine blur at any location in the image.