Focus & Aperture Quality – MultiTest

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

The Focus & Aperture Quality chart shows the expected sharpness across the focus adjustment range.

Key:

• Red diamonds: quality of AF points (wide open)
• Small Purple circles: quality as the aperture is changed
• Orange line: quality with the lens aperture wide open
• Pink line: quality when focused wide-open, but then stopped down to f/8

Interpretation

The red diamonds represent the measurement quality for a number of autofocus measurements at the specific focus adjustment value (these identical in nature to the points shown in the Calibration test).

The small purple circles show the quality as the aperture is changed from wide open the smallest aperture tested (f/16 by default). All lenses get sharper as the aperture is closed down, so the purple dots show the increase in quality (with no focus adjustment) that you get from stopping the lens down. The peak value of sharpness is indicated by the topmost points (and this is shown by the quality line on the various 2D colour grids).

An asymmetry in the peak points indicates that the sharpest images will be obtained with a little manual focus adjustment rather than using pure autofocus – in the example above, the left-most peaks of the purple dots is significantly higher than the right most points, so the best quality will be obtained by shifting the focus a little towards the camera (negative focus adjustment value) from the wide-open autofocus result that would usually be used by the camera.

The orange line shows the modelled sharpness values across the focus adjustment range with the lens wide open.

The best focus adjustment setting is the point where this curve is highest, and is indicated by the green vertical line.

The pink line shows the modelled sharpness values with the lens at f/8 (but when focused wide-open). This should always be a shallower curve, with higher values at the far left and right extremes. The peak point will not always be at the same spot at the wide-open curve, indicating some degree of focus shift.

Aperture Range Quality Score (ARQS) – MultiTest | This Page | Aperture Sharpness Profile – MultiTest