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+--- Thread: Sony FE 28mm f/2 in da lab (/showthread.php?tid=4632)
RE: Sony FE 28mm f/2 in da lab - Brightcolours - 01-19-2020
(01-19-2020, 05:59 PM)Rover Wrote: Can distortion be variable from copy to copy? O_o I mean, from one healthy copy to another, not counting damaged or badly decentered lenses.
No.
RE: Sony FE 28mm f/2 in da lab - JJ_SO - 01-19-2020
(01-19-2020, 05:57 PM)Brightcolours Wrote: Distortion will NOT vary from copy to copy. ...
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.
RE: Sony FE 28mm f/2 in da lab - Brightcolours - 01-19-2020
(01-19-2020, 07:41 PM)JJ_SO Wrote:I can't help it that you find it hard to believe.(01-19-2020, 05:57 PM)Brightcolours Wrote: Distortion will NOT vary from copy to copy. ...
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.
RE: Sony FE 28mm f/2 in da lab - JJ_SO - 01-19-2020
The usual answer to avoid delivering evidence. Nothing unexpected.
RE: Sony FE 28mm f/2 in da lab - Klaus - 01-20-2020
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.
RE: Sony FE 28mm f/2 in da lab - JJ_SO - 01-20-2020
(01-20-2020, 06:30 AM)Klaus Wrote: 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.
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...
RE: Sony FE 28mm f/2 in da lab - thxbb12 - 01-20-2020
It seems likely to be variations in the way things are setup'ed.
RE: Sony FE 28mm f/2 in da lab - Rover - 01-20-2020
(01-20-2020, 08:52 AM)thxbb12 Wrote: It seems likely to be variations in the way things are setup'ed.
Like distance between the chart and the gear during the testing?
RE: Sony FE 28mm f/2 in da lab - Brightcolours - 01-20-2020
(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.
Of course, there'll be slight variations - lenses aren't digital after all - but there'll be no qualitative difference.
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...
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.
RE: Sony FE 28mm f/2 in da lab - toni-a - 01-20-2020
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 ?