Side Imaging vs Down Imaging: Which Sonar Do You Need?
Side imaging vs down imaging explained in plain English: what each view shows, when each finds more fish, and whether you need both on your fish finder.
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The short answer
Down imaging shows a detailed picture directly under your boat, which is great for vertical fishing and reading bottom. Side imaging shows a wide picture to the left and right, which is great for finding brush, docks and schools fast. Most bass and crappie anglers benefit from both; deep-water jiggers can skip side imaging.
Our top picks
- Pick side imaging if… you scan shallow cover and want to find spots fast: Humminbird HELIX 7 MSI GPS G4. Check price on Amazon
- Pick down imaging if… you fish vertical or on a budget: Humminbird HELIX 7 MEGA DI GPS G4. Check price on Amazon
- Both, budget: Garmin ECHOMAP UHD2 74sv with ClearVü and SideVü. Check price on Amazon
| Feature | Down imaging | Side imaging |
|---|---|---|
| Where it looks | Straight down, narrow slice | Left and right, wide swath |
| Best for | Bottom detail, vertical jigging, ice-like fishing | Finding cover, docks, schools, mapping a bank |
| Speed to use | Any speed | Best around 2 to 6 mph |
| Learning curve | Easy | Moderate |
| Transducer size | Smaller | Larger, longer |
| Cost | Budget to mid-range | Mid-range and up |
How we built this guide
We used manufacturer sonar specs, published frequency and range data, and owner reports from bass, crappie and walleye anglers. We have not done hands-on testing, so we lean on documented performance and common owner experience.
What does down imaging actually show?
Down imaging shows a photo-like slice of what is directly below the boat. It is excellent at showing bottom hardness, stumps, brush and baitfish under you.
Brands use different names: Humminbird calls it Down Imaging or MEGA DI, Garmin calls it ClearVü, and Lowrance calls it DownScan. It uses a thin, high-frequency beam. That thin beam gives sharp detail but only covers a small area.
Real-life example: you are sitting on a deep brush pile in 25 feet. Down imaging shows each branch and the crappie suspended in it.
What does side imaging actually show?
Side imaging shows a wide view off both sides of the boat, often 100 feet or more each way at practical settings. It is the fastest way to find cover you cannot see.
Humminbird calls it Side Imaging or MEGA SI, Garmin calls it SideVü, and Lowrance calls it SideScan. You idle along a bank and see every dock piling, laydown and rock pile on the screen. Then you mark a waypoint and come back to fish it.
Humminbird HELIX 7 MSI GPS G4
A popular way to get MEGA Side Imaging on a 7-inch screen. It also includes down imaging and CHIRP, so you get all three views.
Check the Humminbird HELIX 7 MSI GPS G4 on Amazon →
Do I need both?
If you fish shallow to mid-depth cover, yes, both together are the sweet spot. If you mostly fish deep open water, down imaging plus CHIRP is enough.
Side imaging finds the spot. Down imaging and 2D CHIRP confirm what is on it. Many owners say side imaging changed how they find new water. Others who fish deep reservoirs for walleye say they rarely use it.
Humminbird HELIX 7 MEGA DI GPS G4
This model drops side imaging but keeps MEGA Down Imaging and Dual Spectrum CHIRP. It is a smart choice for vertical anglers who want to save money.
Check the Humminbird HELIX 7 MEGA DI GPS G4 on Amazon →
Garmin ECHOMAP UHD2 74sv
The sv models include both ClearVü and SideVü with the GT54 transducer. You also get Garmin Navionics+ mapping on this US bundle.
Check the Garmin ECHOMAP UHD2 74sv on Amazon →
Who it’s for / who should skip it
- Side imaging is for: bass anglers, crappie anglers fishing brush and docks, and anyone learning a new lake.
- Down imaging is for: vertical jiggers, deep-water walleye anglers and budget buyers.
- Skip side imaging if your boat or kayak has no good spot for a large transducer, or you fish mostly deep open water.
What actually matters when buying
- Frequency: higher frequency gives more detail but less range. Mega or UHD frequencies are best for shallow detail.
- Screen size: side imaging needs room. 7 inches is the practical minimum, 9 inches is better.
- GPS: side imaging is far more useful when you can mark what you see.
- Marketing noise: “range up to” figures are best-case numbers in clear water.
Watch-outs
- Side imaging gets blurry at high speed. Slow down to scan.
- Turning distorts the image. Run straight lines.
- Side imaging transducers stick out further and can get hit by stumps.
- Learning to read shadows takes a few trips. See our how to read a fish finder guide.
Which should you choose?
- Choose side and down imaging if you fish cover in under about 40 feet.
- Choose down imaging only if you fish vertically or deep and want to save money.
- Choose forward-facing sonar later if you want to watch fish react in real time. See our live sonar roundup.
Common questions
Can side imaging see fish?
Yes, fish show up as small white dots with shadows. It is easier to see schools and big fish than single small ones.
How fast should I go when side imaging?
Many owners report best results around 3 to 5 mph. Check your manufacturer’s guidance, since higher speeds stretch and blur the picture.
Does down imaging replace 2D sonar?
No. 2D CHIRP still shows fish arches and bait better at depth. Most anglers run down imaging and 2D side by side.
Is side imaging worth it on a kayak?
It can be, but the transducer is larger and harder to mount. Many kayak anglers choose down imaging for simplicity.