Humminbird 141c - Manual (Page 57)

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from an object meets strict parameters, the unit draws a Fish Symbol (or icon) and the
digital depth of the target. On DualBeam and DualBeam PLUS™ units, fish detected in
the narrow center beam are shown as shaded symbols, and fish detected in the wider
beam are shown as hollow symbols.
Fish Symbol: A Fish Symbol is the graphic that is displayed on the screen when Fish ID+
determines that a sonar return is likely to be a fish. See Fish ID+.
Freeze Frame: Freeze Frame is a Humminbird® feature that pauses the sonar scrolling so
that the image on screen can be studied with greater detail. See Instant Image Update.
Frequency: Frequency is a measure of the number of sound wave cycles per second of
a sound impulse transmitted underwater. A typical frequency for fishfinders is 200
kHz, which offers a good balance of performance under many conditions. Lower
frequencies, such as 50 kHz, are capable of penetrating to greater depths, but with less
resolution. Higher frequencies, such as 455 kHz, offer greater resolution, but are
limited in depth performance. Humminbird® uses a variety of frequencies that are
optimized for specific applications.
Grayscale: Grayscale is the use of varying shades of gray to represent the strength of the
sonar signal on the display, and is a very intuitive method of presenting information.
Traditionally, the strongest sonar signals are represented in black, and progressively
weaker signals are represented in progressively lighter shades of gray.
Grayscale, Inverse: Inverse Grayscale is a Humminbird® feature that reverses the
correlation of sonar signal strength and the shade of gray typically used to represent it.
The strongest sonar signals are represented by "white", and progressively weaker signals
are represented in progressively darker shades of gray. While somewhat counter-intuitive,
this method makes the sonar images crisper, and has the benefit of enhancing the
apparent sensitivity because the weaker signals appear bolder. Inverse grayscale works
well in very clear water. Debris-laden water often appears as a lot of clutter on the screen.
Instant Image Update: Instant Image Update is a Humminbird® feature that updates all
the sonar information on the display when Sensitivity and a variety of sonar settings
(Bottom View, Range, etc.) are modified. This differs from the traditional functionality
that only updates the new sonar information collected after the setting change. Instant
Image Update permits more accurate fine-tuning of the display because the user can
see the results on the complete sonar graph. When combined with the Freeze Frame
feature, the user can adjust and understand the effects of many different sonar settings
quickly and easily.