A few screenshots from my latest outing, way to deep for most of you guys but who knows, maybe a pelagic troller comes passing by. ;) Depth in meters. so multiply by three to get feet. Temp in celsius. Equipment used here is Lowrance Sonarhub with Airmar TM185HW connected to Lowrance HDS Gen 3, all running latest software.
Everything in auto exept the watercoloumn which is set to 20-40 meters since that is where the action is. Ping is 14 and scroll is 1/2:
Notice the change here, still in auto-mode. But I`m viewing the whole watercoloumn and it is 20-ish meters deeper. Result: less resolution than in the screenshot above.
Resolution is about more than the number of pixels in your screen. It is also about the resolution within the processed sonar-signal (target-seperation) and how much of the watercoloumn you are looking at. These three add up, so having a full HD-screen will not give you any value if your target seperation is crap or you are trying to view 3000 meters of watercoloumn at once. With my combination of Sonarhub and TM185HW, there is a drastic change in resolution when depth exceeds 80-90 meters, and from there and towards even deeper water I switch to manual mode to combat that.
Her I`m going from auto to manual mode, notice the difference in resolution.
When putting your sonar in manual mode, the signalstrength is adjusted to the range you set as depthscale, while in auto it is adjusted to whatever the sonar thinks is bottom. Even with chirp, that means greater depth = less resolution. So the next time you venture out in deeper water, but is mostly interested in pelagic-species, try using your sonar in manual-mode and adjust the depthrange.