EXCERPT page containing first few paragraphs. 2019-02-15 12:09:11
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This series confirms a pronounced rearward focus shift with the 15/1.7, which is hugely destructive to image sharpness if not accounted for.
Two large actual pixels crops are provided.
Both crops provide near-to-far context showing a pronounced rearward focus shift with stopping down. On the MFT format, depth of field is deep (see format depth of field), so to see this visible a shift is surprising. In your author’s view, significant focus shift is an unacceptable design tradeoff, because it is so destructive to image sharpness.
Focus shift aside, observe inadequate control of secondary longitudinal chromatic aberration; that veiling purple/magenta haze seen on the leading block at bottom. Other scenes confirm this weakness; the 15/1.7 can be expected to show pronounced violet fringing on backlit subjects even to f/5.6. This behavior is not a crowd pleaser.
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