How can you compensate for lens focus shift when shooting film or digital?

Asked 1/11/2014

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Some lenses with residual spherical aberration can shift focus backward as you stop down, especially at close distances and at mid-to-wide apertures. This is often a characteristic of the design rather than a defect. What practical techniques do photographers use to work around focus shift on cameras without through-the-lens stopped-down preview, such as film rangefinders? And how is it handled on digital cameras?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

12y ago

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With a digital SLR there are several advantages your film rangefinder doesn't share. Combining Live View with the depth of field preview button (or any other setting that stops the lens down while viewing the scene via Live View) allows for precise manual focusing, usually with the subject magnified 5x or 10x on the camera's rear LCD. Another advantage is being able to instantly review the image and compensating for a follow up shot when the camera and subject are both static. The combined result of these advantages is that learning to shoot "blind" with such a lens is a dying art.

Before the advent of digital cameras in the hands of most every shooter, there were several ways to deal with the issue of focus shift.

  • Don't worry about it. Expectations in terms of resolution and print sizes were often much lower before the advent of the megapixel race. Going back and examining some (but not all) works considered masterpieces from previous eras reveals a lack of tack sharp resolution that is surprising to our eyes.
  • Experience/trial and error. Although the feedback from each attempt took longer than the near instantaneous results of the digital age, many owners of such lenses learned how to use them this way. Often entries for each exposure were made in log notebooks so that when the results were viewed later they could be interpreted in light of the various amounts of compensation tried at various apertures and focus distances.
  • Systematic charting. The results from shooting at test charts to document the amount of shift using various combinations of apertures/subject distances were compiled into a chart that could be used to predict the amount of shift. Some lenses were supplied with such testing information when they were new, or the manufacturers otherwise made it available to the owners of their lenses.

Originally by user15871. Source · Licensed CC BY-SA 4.0

user15871

12y ago

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AI Answer

Generated from our catalog & community — verify before relying on it.

Yes—photographers do compensate, but the method depends on the camera.

On digital SLRs, the easiest approach is to focus at the taking aperture using Live View and a stopped-down preview, ideally with 5x or 10x magnification. That lets you see the actual focus position at the aperture you’ll use. If the subject and camera are static, immediate review also helps you refine focus on a second shot.

On cameras where you must work “blind,” such as a film rangefinder, there’s less direct feedback. In practice, photographers either learn the lens’s behavior through experience or simply don’t worry too much about it. Historically, many people accepted small focus shifts because viewing and print expectations were less demanding than today.

So the practical answer is:

  • digital: use Live View, stop-down preview, magnified manual focus, and review
  • film/rangefinder: learn the lens’s tendencies, shoot accordingly, and accept that some focus shift is part of the lens’s rendering

If the lens is valued for its look, many photographers consider that tradeoff worthwhile.

UniqueBot

AI

12y ago

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