Zeiss 50mm 1.5 on GXR

Started Dec 13, 2011 | Discussions thread
Godfrey Forum Pro • Posts: 29,439
Re: Zeiss 50mm 1.5 on GXR

monoblocks wrote:

It is a fact that Zeiss 50mm has focus shift issue when mounted with rangefinder camera. Since GXR uses a completely different method to focus, does it mean that the back focus issue with this lens will not exist when used with cameras like GXR or other micro four third models?

Focus shift means that the focus point shifts as the aperture changes. This can be a problem on rangefinder (and SLRs with auto-diaphragm operation). A lens which focus shifts is a problem to work with on a rangefinder camera because the rangefinder mechanism has no way of knowing where the correct focus point is if it changes as the lens is opened up or stopped down. The same is true on an auto-diaphragm SLR lens which focus shifts ... the focusing system or your eye sets a sharp point, at the moment of exposure the lens stops down and the focus point has shifted.

With the GXR-M (and other mirrorless interchangeable lens cameras) you normally look through the lens set to the taking aperture. Because of this, whether the lens focus shifts or not is not relevant to your focusing operation ... you're always going to be making the image sharp no matter what, and the aperture isn't going to change. It's only if you open the lens up to focus and then close it down to make the exposure that focus shift can throw your focus setting off.

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