Front Focus

BackdoorArts

BackdoorArts

Senior Member
It means the autofocus locks at a point in front of where you expected it to focus. Back-focus is in the opposite direction. In most current cameras this can be corrected using the AF Fine Tuning in the camera, though with zoom lenses you can have a combination of front and back focus throughout the range of the zoom so you have to decide how best to tune it (in general it's best to measure across the range and pick something that is either common to most focal lengths or err on the size of the long end because depth of field is most shallow there and you may be more apt to use bigger apertures).
 
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Bikerbrent_RIP

Senior Member
Yes, prop up a 12" ruler at a 45 degree angle (with the 12" mark at the top) next to a box or book with fine print details aligned with the 6" mark (front of book or box at 6" mark). Auto focus on the book or box or make sure the ruler is in the scene. Take a picture with the lens set at minimum f stop. If the 6" mark is sharp, you are good to go. If the ruler mark less than 6" is sharp, you have front focus. If the ruler mark greater than 6" is sharp, you have back focus.
 
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mikew_RIP

Senior Member
You would have to find out if and by how much it was out at 300mm,then decide if a adjustment would hurt the other focal lengths,i did all my 500 and 600mm at full zoom and it never hurt the other settings.
 
BackdoorArts

BackdoorArts

Senior Member
There's a chart you can print on this video if you want to do it without any calibration tools. Guy's a pompous ass but nonetheless he has some useful info. You can use a ruler too. He's not clear on it, but even though he has you setting the focus point in Live View make sure you refocus when it's not because that's the part that needs calibration.

 
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