Lens sample variation

[JamesA]

Kind of odd how there are no standards (it seems) when it comes to testing equipment.  Lenses in particular.  Each review site seems to come up with it's own particular results, most of which do not really match with each other.  I'm wondering about sample variations?  I know that the grinding of glass lenses has improved in the past 30 years with computer-controlled equipment so I'd expect spherical glass optics to be better and more uniform, but how about the use of molded plastic and glass for aspheric elements?  Likely, there is a wider variation producing these than grinding a spherical lens so I'm wondering if that could account for the sample variations we see now?

[walter.sk]

Kind of odd how there are no standards (it seems) when it comes to testing equipment.  Lenses in particular.  Each review site seems to come up with it's own particular results, most of which do not really match with each other.  I'm wondering about sample variations?  I know that the grinding of glass lenses has improved in the past 30 years with computer-controlled equipment so I'd expect spherical glass optics to be better and more uniform, but how about the use of molded plastic and glass for aspheric elements?  Likely, there is a wider variation producing these than grinding a spherical lens so I'm wondering if that could account for the sample variations we see now?

I wonder if the apparent differences between samples of the same lens have more to do with tolerances of focus calibration.  It is possible to get a camera that is at one end of the tolerances and a lens that is at the other, both within factory specs but whose errors add up rather than cancel each other out.  I had a Canon "L" lens that seemed soft with my 1DMkII, and had both the camera and lens recalibrated by Canon.  The difference in sharpness was significant.

[telyt]

Kind of odd how there are no standards (it seems) when it comes to testing equipment.  Lenses in particular.  Each review site seems to come up with it's own particular results, most of which do not really match with each other.  I'm wondering about sample variations?  I know that the grinding of glass lenses has improved in the past 30 years with computer-controlled equipment so I'd expect spherical glass optics to be better and more uniform, but how about the use of molded plastic and glass for aspheric elements?  Likely, there is a wider variation producing these than grinding a spherical lens so I'm wondering if that could account for the sample variations we see now?

Manufacturing tolerances play a big role too: centering & accurate spacing for example.