Focus shift or a rangefinder calibration problem?

[TomB_tx]

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20 hours ago, pippy said:

A few years ago I put a dozen or so non APO/ASPH/FLE lenses through a tightly controlled studio-based test whilst shooting a Focus Calibration Test Card and every single one of them showed focus-shift when using different apertures and using different focussing distances. Some, admittedly shifted more; some shifted less. But all exhibited focus-shift to some extent

I agree - every fast lens (2.0 & wider) I've checked also has some focus shift when stopped down, to varying degrees. Typically the increasing DOF covers it well, so it goes un-noticed, while others shift more noticeably. The Nokton 35 f1.4 ver 1 has significant shift - but I used one foe some time without noticing it. The Heliar 50 f2.0 Nickel had the most that I had found, but again I got many good pictures from it. You are more likely to notice if you pixel-peep on digital. If I had't bothered to set up a focus chart and test carefully I would not have noticed this on most lenses.

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[pippy]

45 minutes ago, TomB_tx said:

...You are more likely to notice if you pixel-peep on digital. If I had't bothered to set up a focus chart and test carefully I would not have noticed this on most lenses...

Apparently the issue of focus-shift (at certain apertures and certain subject-distances) only really became evident because after digital arrived it was possible to pinpoint this phenomenon for what it was. Previously no-one really noticed because any slight softness in IQ might be down to critical sharpness being "lost in the grain" and any slight discrepancy with pin-sharp focus could simply be down to marginally mis-focussing or perhaps un-noticed but slight camera-subject movement change at the shooting stage.

Digital Photography arrived and, for the first time, it was possible to do - and check - so many things with an accuracy which had never been possible before and so there arose a need to 'Do Something About It' - hence the arrival of such a glut of APO / FLE / ASPH lenses on the market.

All the older generation of lenses still behave in exactly the same way as they always have done. For some situations the increase in IQ on the technical side is an absolute blessing. We now have access to lenses useable on '35mm Format' cameras which can produce results of a quality previously only available to those shooting in medium-format (or larger).

At the same time these same cameras can not only replicate the well-loved results due to the inherent aberrations of the older generations of lenses but they can enhance their inherent characteristics in a way which can let them be appreciated all the more fully.

Philip.