DotTune

October 21, 2014  •  Leave a Comment

What is DotTune

DotTune is a method to set AF fine tune for a given lens on a given camera.  The technique was first proposed by Horshack on DPReview in this post and at Fred Miranda for Canon and Nikon.  The technique uses the green focus dot in the viewfinder to determine the correct focus, based on changing AF fine tune values.  This works because the camera (Nikon and Canon) use the AF fine tune value as an adjustment before focusing.

Procedure

  1. Pick a high contrast target with both vertical and horizontal lines under bright, consistent light at greater than 50X focal length distance and lock down your tripod.  Focus on the subject using live view to establish critical focus.
  2. Canon: Set the lens to manual focus and set the AF mode to single shot.  Nikon**: Keep the body and lens in AF mode, set AF activation to AF-ON only and focus mode to AF-S.
  3. Use the shutter button half press and check the focus dot in the viewfinder.  Try different AF fine tune values to bracket the focus range.  You are out of range if there is any delay or flicker in the rangefinder dot (or arrows on Nikons).  The dot must stay steady for 5 seconds.
  4. Set the AF fine tune to the middle of the focus range determined in step 3.

*Using a greater target distance tends to work better than a close distance.  The adjustment might vary by distance, but longer distances adjust better to shorter distances than the converse.

** Nikon cameras use a less sensitive focus indication when the focus is set to manual.  To get around this limitation set the focus activation to the rear AF-ON button and then use the shutter half press to check the focus dot.  This will activate the focus dot without focusing the lens.


Comments

No comments posted.
Loading...

Archive
January February March April May June (1) July August (1) September October (1) November December (1)
January February March (2) April (1) May June (1) July August (3) September October November (1) December
January February March April May (2) June July August September October (2) November December (1)
January (1) February March April May June July August September October November December
January February March April May June July (1) August (1) September (1) October November December
January February (2) March (1) April May June July August September October November December