Aperture Sharpness Profile – MultiTest - Reikan FoCal Help

Aperture Sharpness Profile – MultiTest

(See Chart Features for general chart features - changing scales, copying to clipboard etc)

The Aperture Sharpness Profile chart shows various view of the sharpness across the aperture range.


  • Red line: uncalibrated aperture sharpness (adjustment value is 0)
  • Green line: calibrated aperture sharpness
  • Black dotted line: sharpness obtainable with manual focusing at any aperture
  • Orange dotted line: aperture at ARQS calibration value (see below).


The chart above shows 4 different views of the sharpness across the aperture range.

The Uncalibrated line shows what a straight-out-the-box lens would be able to achieve.

The Calibrated line shows the result when the lens has been calibrated for best sharpness wide-open (the left most green point will be at the highest value of all the left-most points).

There is usually a little difference between uncalibrated and calibrated results, with the calibrated results almost always being better than uncalibrated.

Things start getting interesting with the other two data sets:

Manual Focus

If you were to use Live View, magnify and manually focus at a specified aperture to the best possible sharpness, the quality you’d be able to achieve is represented by the black dotted line on the chart.

This is the highest quality achievable at any aperture.

The difference between the black and the green lines at any aperture point shows the quality you will lose by autofocusing on the subject, even with a calibrated lens.


The Aperture Range Quality Score focus offset value is designed to optimise the best average quality across the whole aperture range. This is shown with the orange dotted line.

You can see from the chart above that it sacrifices some of the wide open quality, but once you stop down to f/3.5 the quality is better – between f/3.5 and f/8 the quality difference is quite significantly better when using the ARQS focus value.

The ARQS chart can give a different view of the data – see here for more info Aperture Range Quality Score (ARQS) – MultiTest

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