01-19-2020, 07:40 PM
Sony FE 28mm f/2 in da lab
01-19-2020, 07:41 PM
That's a statement I find hard to believe. Everything varies, especially centering and resolution. if these properties are variable in each specimen, I see no reason why distortion is not affected.
Also, using the same software doesn't mean the setup for each lens test (site) is identical. The software programmers don't deliver the full hardware equipment, do they? Maybe I'm wrong but a lot of these testers don't appear to have a solid professional background as optical engineer.
01-19-2020, 07:46 PM
(01-19-2020, 07:41 PM)JJ_SO Wrote:I can't help it that you find it hard to believe.
01-19-2020, 08:50 PM
The usual answer to avoid delivering evidence. Nothing unexpected.
01-20-2020, 06:30 AM
Distortions will not vary between samples in any substantial way.
Of course, there'll be slight variations - lenses aren't digital after all - but there'll be no qualitative difference.
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01-20-2020, 08:23 AM
(01-20-2020, 06:30 AM)Klaus Wrote: Distortions will not vary between samples in any substantial way.
Can you quantify the "non-substantial" way? To me the diff between -1.28%, -1.35% makes 0.07%. I would not call that "substantial". That was my reason to ask for sample variation. Be it that, or variation in measuring method, I still don't believe that distortion is absolutely excluded from any variation. The differences might be very small and neglible, but there's absolutely no reason why this property should not be affected. There are differences in resolution big enough to appear on charts...
01-20-2020, 08:52 AM
It seems likely to be variations in the way things are setup'ed.
01-20-2020, 10:23 AM
01-20-2020, 11:10 AM
(01-20-2020, 08:23 AM)JJ_SO Wrote:(01-20-2020, 06:30 AM)Klaus Wrote: Distortions will not vary between samples in any substantial way.
Decentered elements impact sharpness, but not things like focal length or distortion. With no decentered elements you see very little difference in sharpness.
Lens elements get made (and always have been made) with a lot of precision, you do not see different focal lengths, different distortion or differences in chromatic aberrations between lens samples unless the geometry has been seriously damaged.
01-20-2020, 11:48 AM
I guess the size of the chart used is important, if you change chart size, you change shooting distance, and this will eventually change everything, not sure however if distortions vary with shooting distance, do distortions differ when we shoot at infinity versus MFD ?
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