Device Settings Step Size and Range Settings
Device Settings

Information in this article applies to:

  • uScope Navigator V4.0 and Later

Article ID: NDS1154 — Created: 23 Feb 2018 — Reviewed: 8 Aug 2021


In the Device Settings for the uScope, there are a number of options that specify a Step Size and a Range. What is the meaning of these settings?


The Step Size is the minimum amount of movement (up or down) the objective makes when changing focus while the Range is the maximum amount of movement the objective makes when changing focus.

The following sections provide more information about the Step Size and Range settings.

Step Size

The objective moves up and down under the power of a stepper motor. The stepper motor moves in increments called steps. All Step Size settings specify the number of motor steps to move the objective.

The following table lists the single step measurement for all uScope models.

uScope ModelSerial Number
Step Size
(In Microns)
uScopeMXIIM2B, M2C, M2D≈0.1984
uScopeHXIIH2C, H2D≈0.1984

The Step Size used in the Device Settings is typically set to a value based on the depth of field of the objective (which is based on the objective magnification and numerical aperture). The following table lists default step size settings.

ObjectiveDepth of FieldDefault
Step Size
10x≈2.0 microns10
20x≈1.2 microns6
40x≈0.6 microns3
60x≈0.4 microns2

Refer to the following knowledge base articles for a step size calculator you can use to accurately determine step measurements:


A focus range is used when attempting to acquire focus in a variety of scenarios:

  • Acquiring auto-focus,
  • Fast Stack focus method (when scanning),
  • Predictive focus method (when capturing prediction points),
  • Exhaustive Stack focus method (when scanning),
  • Predictive Stack focus method (when scanning & capturing prediction points).

The Range specifies the distance (in motor steps) above and below a mid-point. So, a range setting of 100 is equivalent to 201 steps in total (100 motor steps above and 100 motor steps below a mid-point).

The Range is typically set to help the focus algorithm achieve final focus. The following table lists several common range settings.

Range Setting
(In Steps)
Complete Range
(In Steps)
Range Size
3061≈12.1 microns
78157≈31.2 microns
100201≈39.9 microns
120241≈47.8 microns
5001,001≈198.6 microns


Be cautious when extending the range of auto-focus. Typical slides have a cover slip that is 170µm thick. Extending the range of auto-focus too much can cause the uScope to focus on dirt and debris on top of the cover slip rather than on the specimen.

  • For the Exhaustive Stack focus method, reducing the range size can reduce the scan time especially for very flat, thin sections.
  • For the Fast Stack & Predictive Stack focus methods, reducing the Fast Stack run range reduces the scan time.
  • For the Predictive & Predictive Stack focus methods, reducing the Predictive run range reduces the time required to acquire the prediction points but should be used only for very flat sections.
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