Case in point, the photo above. I snapped the shot in April on a friend's boat. He had the finder so tweaked that it picked up our jigs streaking up and down. A few months ago, I went on a walleye trip where the captain had side-imaging sonar, which is the latest and greatest advance in this technology. The screen showed a perfectly crisp portrait of the river bed, and there, next to a boulder was a walleye plain as day. I cast to the boulder, and just like that the walleye disappeared as I fought it to the boat.