Patch / Aperture Size requirements - X-Rite eXact

Maximal Aperture Size Recommendation

  Spot Mode Scan Mode
Patch Size Spot only*
(max aperture size)
Strips < 10cm/4"
(max aperture size)
Strips 10cm/4" to 75cm/30"
(max aperture size)
Strips > 75cm/30"
(max aperture size)
2mm 1.5mm - - -
3mm 2mm 1.5mm - -
4mm 2mm 2mm 2mm -
5mm 4mm 2mm 2mm 2mm
6mm 4mm 4mm 4mm 2mm
7mm 6mm 4mm 4mm 4mm
8mm 6mm 6mm 6mm 4mm
>= 9mm 6mm 6mm 6mm 6mm

* For spot readings, it is always recommended to use the largest aperture size possible.  If the instrument is used for scanning as well, scan mode will dictate the aperture size.

Aperture Specifications

Aperture Size Measurement
area size
Opening in
target window**
Opening in scan chassis target window Screening Range
1.5mm 1.5mm 3.5mm 4.0mm 175 lines/inch or 69 lines/cm or above
2mm 2.0mm 4.0mm 4.5mm 133 lines/inch or 52 lines/cm or above
4mm 4.0mm 6.0mm 6.5mm 65 lines/inch or 26 lines/cm or above
6mm 6.0mm 8.0mm 8.5mm  

** For each eXact aperture size, the target window size is 1 mm (on radius) larger than the spot measurement area size. This 1 mm over iluumination of the measurement area is required by ISO5/4. The white area around the patch, does not influence the measurement data, but does require the operator to center the measurement sample in the target window opening.

The illustration below shows how this minimum measurement area appears in relation to the target window opening.

The black circle represents the target window opening.

The white circle represents the actual measurement area (which equals the aperture size).

The magenta square represents the minimum suggested patch size.

This can be used as a guide for operators when placing the instrument optics over patches which do not completely fill the target window opening.


eXact Aperture Sizes

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