Front and Back Focusing calibration.
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What is Front or Back focusing?

 

Front focusing is when the lens and camera focus in front of your planned target point. Your planned target will look a tad out of focus while the area in front of it will be in focus.

Back focusing is when the lens and camera focus behind your planned target point. Your planned target will look a tad out of focus while the area behind it will be in focus.

It could be caused by a moving subject after the focus was locked on that subject. Take the picture again and if the problem persists, you might have a focusing problem.

Lenses are calibrated at the factory and so are the cameras.  There are tolerances, which are proprietary to each company. As an example, let’s assume that the tolerances are plus/minus 1.5%, for each the camera and the lens. A focus problem could develop when a camera is calibrated on the + side and an attached lens is also factory calibrated on the + side. This can cause a focusing problem. Modern cameras have built-in software to fix some of the lenses tolerance so that the combination of the camera and lens are within acceptance. If both are at + 1.5%, the combination being + 3%, it could create focusing problems. On the other hand, if the camera is at the + 1.5% and the lens is at – 1.5%, it is assumed that the tolerance would be at 0%, and the focusing should be accurate.

Autofocus Fine Adjustment

 

If you experienced front or back focusing problems with your Pentax attached lens, you might be able to fix it yourself.

 

Depending on your Pentax DSLR model, the AF Fine Adjustment is usually located in the Custom Settings Menu under the ″AF Fine Adjustment″.

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Front and Back Focusing calibration.

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