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This post might be called Dr. Strangelens, or, How I Want To Stop Worrying About Focus Shift. I've decided to focus (pun intended) on my Leicas after a several years favoring another camera. I love the rendering of my pre-FLE Summilux ASPH (bought new in early 2000s). But it has noticeable focus shift. I realized that I could compensate by focusing slightly closer than the intended subject at middle apertures. But I didn't want to deal with that in fast situations. I also picked up a used 50/1.2 Nokton v.1. It had no appreciable focus shift, but has a duller rendition than the 'Lux, weighs a ton, and blocks too much of the viewfinder. So I only use the Lux at f/1.4, 2.0 and 8. And I've ended up with a set of "available light" lenses and an other set for outdoors. Fast forward to today. I retested the 'Lux on my current cameras (M10p and the M(9)M "Henri" Monochrom). I taped a tape measure to the floor, and set up a tripod 1.1 meter away, looking down diagonally. Nothing had really changed, of course. And then I decided to test all my lenses. Both my 35mm and 50mm 1980s Summicrons showed front focus at full aperture, especially the 35. At f/2.8 and smaller, they are both fine for all practical purposes. Then I used my Visoflex to focus them. It turns out that they are not soft wide open as I had thought. They are actually only a little softer than at f/2.8, but they are focusing closer than the RF indicates. It turns out most of my f/2 or faster f/2 or faster lenses have some focus shift. Except for modern Voiglander Noktons. And one surprise: my 1947-vintage Summitar. Go figure. The question is, how much does it really matter? I need a real-world benchmark. My experience tells me that if I can't see unsharpness when a file is blown up to 50%, or can just barely see it, it doesn't matter at the size that most of us display or print. Is this a reasonable standard? Years ago, conventional wisdom was that Leica lenses were perfect and all unsharpness was user error. That might have been believable with film, which has thickness and grain. But not with digital. And we now have the ability to pixel peep beyond all reason. Thoughts and advice welcome. --Peter
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