I've had a lot of questions lately regarding the screen shots and detail on our Humminbird units. I've used a lot of the manufacturers out there, and I have to say I'll put our Humminbirds up against ANY of them! Here the settings we use:
Settings
Switchfire - We run Max Mode when over 20'. Here's an explanation of what Switchfire is - Clear Mode looks at the most intense part of the sonar beam where as Max Mode is unfiltered data so it will incorporate side lobes. Max mode does adjust power output for depth. Clear mode can adjust output power to match the depth. Plus Clear mode also provides Time Variable Gain so it understands the loss of sonar signal strength over depth and in Clear mode it can calculate this diminishing return and adjusts the data to display the return as the same size on the screen no matter the depth. so a 5 pound fish will be displayed the same size at 5' as at 50' or 100' or 1000' so you can better determine and compare the sizes, Clear mode is a very precision sonar system where Max mode displays all the data as it naturally occurs.
Water Type - Salt Deep
Transducer Type - Dual Beam (stock ducer is 83/200 if it's an Airmar it'll be a 50/200)
Beam Select - 83/200 or 50/200 depending on your ducer
83 or 50 Sensitivity - 0 to -5
Surface Clutter - 0 to 3
Noise Filter - We would run ours from Medium to High 1 depending on the day. You want to use the lowest setting possible
Sensitivity - Turn it up until you start to see a little "snow" on the screen, and then back it down 1.
Scroll speed - We usually run ours at max speed, but I'm told for the best detail you want to match your speed. If you;re trolling 3mph then set it to a speed of 3. Again, we DON't do this. Just something I've seen in some videos lately.
Jigging Mode - ON if you are seeing a pixilated screen.
Notes
Overlaying your 83 and your 200 beams is nice, but sometimes we see a little better picture when we split the screen and use one side for our 83 (in our case its a 50khz beam) and the other for the 200.
If you can see your cannon balls then you will mark fish. I've had questions regarding this recently. There isn't much of a screen outside of 200' of water on the South shore. If you're seeing your cannon balls don't panic if you're not seeing fish. If you want a warm fuzzy feeling go into 125' or less and look at as many fish and bait pods as you want.
You should be able to see screens like this (these are from the last few weeks):
Lastly, check out some videos on how 2D sonar works if you want to better understand what you're seeing.