Reading the post in the link below,


I was wondering if BACKFOCUS and FRONTFOCUS could be compensated with AF microadjustment (Canon) and AF fine tuning (Nikon) adjustments, using manual focus and not with AF as in the post.

AF microadjustment for canon and AF fine tuning for Nikon can only be used with AF or even when calibrating focus with MF?

Focus calibration with AF also automatically calibrates focus with MF?


No. Calibrating autofocus has nothing to do with manual focus. This is because the light used for autofocus does not follow the same optical path as the the light used for manual focus.

The mirrors of cameras with Phase Detection Autofocus (PDAF) have a mirror that is only semi-reflective in the center. Some of the light is reflected up to the viewscreen. Some of the light passes through the mirror and is reflected down into the AF array by a secondary mirror located behind the main mirror.

When you use manual focus, you focus based upon what you see in the viewfinder which is the image formed on the viewscreen at the top of the camera's light box. If manually focusing to the sharpest focus distance as seen through the viewfinder results in back or front focussed photos, then the position of the viewscreen needs to be adjusted.

AFMA or AF Fine Tune does not do anything to the physical position of anything in the camera. Rather, it is a software adjustment that affects the instructions the camera sends to the lens with regard to the requested position of the lens' focus mechanism.

Keep in mind that AFMA and AF Fine Tune only affect PDAF - that is, focusing done with the mirror down. When using contrast detection AF (CDAF) in Live View, the image sensor is used for both focusing and taking the picture. Since the image sensor doesn't move between focusing and capturing the image, the focus distance needs no calibration. Note than even when in Live View, some cameras have options to do PDAF by dropping the mirror long enough to AF with the PDAF system rather than by using the image sensor based CDAF.

  • Thanks Michael for your detailed answer So, With back focus or front focus problems with manual focus, I have to adjust the display position. But what does the position of the display mean and how does it adjust? – Edward Aug 26 '17 at 9:53
  • the position of the viewscreen, is it related to changing the viewfinder with Live View or is it related to something else? – Edward Aug 26 '17 at 10:04
  • The viewscreen has nothing to do with Live View. It is bypassed when the camera is in Live View mode. The viewscreen is at the top of the light box and is what the mirror projects an image onto when using the viewfinder. When using Live View the mirror is up and no image is projected onto the viewscreen. The image is projected directly onto the imaging sensor and viewed via the LCD screen on the back of the camera. – Michael C Aug 26 '17 at 17:16
  • If you are having front/back focus issues when using Live View then the issue is either 1) The camera is pausing LV just long enough to use the PDAF system (in which case the PDAF system needs to be adjusted), 2) The lens is not holding focus and is allowing the focus to move between the time the camera is focused and the time the photo is taken, 3) The camera to subject distance is changing between the time the camera is focused and the time the photo is taken, or 4) In camera stabilization is changing the sensor to lens distance between focusing and taking the photo. – Michael C Aug 26 '17 at 17:20
  • NOTE: The surface of the viewscreen is one of the most fragile parts of your camera, the other being the surface of the camera's mirror. Touching either one can possibly ruin them. DO NOT attempt to adjust the registration distance of your camera's viewscreen unless you KNOW what you are doing. It's a sure way for most people to make their camera totally unusable. – Michael C Aug 26 '17 at 17:25

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