Humminbird 500 series, 515 instruction

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.

Maximum Depth Menu: The Maximum Depth Menu is a Humminbird® feature that optimizes performance based on the maximum operational depth set by the user. Many Humminbird® units can operate across a very broad depth range (up to 2500 feet) which causes the unit to "look" up to that full depth under some circumstances. Due to the speed of sound in water, this can result in less responsiveness because the unit has to wait for a longer period of time to receive the sonar signal. When the Maximum Depth menu is set to a lower value, the unit only looks up to the setting, which increases the responsiveness of the unit. This is an important feature for anyone operating in shallower depths!

Noise: Noise is unintentional, external sound waves that interfere with the optimal operation of sonar. Noise appears as random "dots" on the display, and is caused by a variety of sources. Electrical noise (from trolling motors, bilge pumps, VHF radios) typically manifests as a consistent dot pattern. Electrical noise can be isolated by selectively turning on and off other electrical devices to determine the source. Often re-routing the power cable, or connecting to an alternative power supply (second battery) can help overcome electrical noise. Hydrodynamic noise (from propeller and/or hull cavitation) has a more random appearance and is generally related to boat speed, so that faster operation results in more noise.