it's on 455 I think had the motor up
The 800kHz frequency will give a more detailed image.......
Choosing frequency is a trade-off decision based on what particular part of the sonar data you want to see at that specific moment....
The 455kHz frequency will usually be brighter all the way out to the sides of the image...but at the expense of filuzzier overall detail....(good for searching and spotting structure farther out to the sides in the SI image)
The 800kHz frequency will be more detailed overall...but it will be at the expense of rendering the outside left and right edges of the image darker...(good for detailed deciphering of structure details closer to the boat...
Here are some comparison shots I took to visually understand this concept...(all conditions and settings were exactly the same except frequency choice...)
*The left image is the 455kHz ..brighter out to the edges - but fuzzier detail...
*The right image is the 800kHz...more detailed and crisper...but darker out to the edges...
Frequency choices are tools (in 2d/DI/ and SI )....
Use each for what it does best
for the task at hand...
Rickie