Side Imaging 101: Guide To Understanding Side Imaging (2024)

Featured Image - CO-0217 - side imaging (2)

If you’re in the market for a fish finder then you are probably considering whether it’s worth getting a side imaging fish finder but what is a side imaging fish finder and does it really help you see and catch more fish?

In my experience, knowing as much as you can about what is in the water around you always helps you catch more fish and when side imaging fish finders first hit the market, I couldn’t wait to get one.

When I did, I started seeing fish on the side imaging sonar I’d have otherwise missed on 2D sonar and my catch rate improved quite a lot.

Join me as we take a look at side imaging sonar fish finders and discuss everything you need to know to be able to decide if a side imaging sonar fish finder is right for your angling needs.

What is Side Imaging?

Side imaging is the exact same as down imaging that you’d find on a regular fish finder with 2D sonar except the sonar beam in the transducer is sent to each side of the boat instead of straight down.

How does side imaging work?

Humminbird Side Imaging
Humminbird Side Imaging

Side imaging works the exact same way as down imaging except, as I mentioned above, the transducer is scanning on each side of the boat to find fish instead of scanning down towards the bottom.

The sonar waves are sent to the side of your vessel at an angle and when reflected produce an image of anything beneath the surface in the entire water column to the left and right of the vessel.


It does not show what’s directly underneath your vessel though as the transducer doesn’t scan that way, only down imaging does that.

This means, when using a side imaging fish finder, you will get side images as well as images of the bottom from, allowing you to get the best possible view of what’s underwater and find fish more easily.

Does Side Imaging show fish?

Side imaging wouldn’t be very useful for fishing if it didn’t show fish, so yes, it does show you a picture of what’s underwater with fish included.

Once you have learned how to adjust the side imaging settings such as side imaging range to the water you’re in and learned how to read a side imaging picture, you’ll be able to see single fish and shoals of fish with side imaging.

How do I see fish on Side Scan?

The key to seeing fish on your fish finder image is by adjusting some settings, in particular, the side imaging range, frequency, and contrast, to the location and water depth you’re fishing in. Once these are honed in, you’ll start seeing fish as white lines in the picture.

Understanding Side Imaging Range

Side imaging range dictates how much distance to the left and right side of the boat you can see on your fish finder images.

The maximum side imaging range on most units is 300 ft scanning to the left and right side of the boat and the minimum is around 50ft.

Range Settings

Lowrance Beam Angle
Lowrance Beam Angle Diagram

When you have your side imaging range set all the up to the max, then you’re seeing very minimal detail of what is in the 300 ft to the left and right of the boat.

You might be able to see structures like rock or brush piles, but your chances of seeing fish are very low as they will get lost in the broad images.

As you lower your side imaging range, to say scanning 75 feet to the left and right of the boat, you’ll begin to see more detail of what’s beneath the surface as the range is smaller and this is when anglers will get a clear view of both fish and structure.


For best results, always make sure your range is set high enough to pick up the bottom though, or you’ll have blind spots in your images and you do this by setting your range to a minimum of 50ft or 3 x the water depth you’re fishing in.

Adjusting The Frequency To See Fish

In order to see fish on the screen with side imaging, you’re going to need to tweak the sonar frequencies as well as adjust the range.

Most side imaging units can push out sonar frequencies of 455 and 800 kHz and if you have mega side imaging, 1 MHz (mega) but what do different sonar frequencies do?

The higher the frequency sonar wave emitted the smaller the distance it will travel but the more detail it will show you.

Fishing Frequency

When you’re fishing, for example, a good frequency to be on is 455 kHz with a range of 200 ft as you get a broad picture on your screen of what’s underwater including structure and depth changes, etc.

When you want to hone into fish, by setting your range to 75 ft as we discussed above and turning up the sonar frequency to 800 kHz, you’re going to see a lot more details and will start seeing fish on the screen in crystal clear images.

Adjusting The Contrast Is The Finishing Touch

Once you have your range and frequencies dialed in, it’s time to adjust the contrast and move around the color palettes for a super clear picture.

This is really easy as on most fish finders you can adjust the contrast while looking at the screen so you will be able to see the difference it makes.

Turn it up or down until you get the clearest picture possible with the right color palette on the screen.

What do fish look like on side imaging?

Anglers often miss fish on their side-scan pictures as they are not sure what they are looking for. When a fish is on your screen it will come up as a white line and sometimes with a shadow too.

If you ever see a small white line then you should assume it’s a fish no matter what. If it was structure or weeds, it would not show up as a white line.

See how fish look like when using side imaging in the video below…

Find fish with Side Imaging | Sonar Shadows | The Technological Angler

Does Side Imaging Work in Shallow Water?

Yes, side imaging works in shallow water, no matter how shallow it is. Even when the water depth is just 2 feet it works.

It also works well in deeper water too as long as it can read to the bottom of the water column and with a max of 300 ft, it goes deep enough for most freshwater fishing and sea fishing locations.

How do you read a Side Imaging picture?

Humminbird Side Imaging Illustration
Humminbird Side Imaging Illustration

When you’re looking at side-scan images, you have to remember that the unit will scan with a kind of fan spread to either side of your boat, and that same area is then portrayed in an image on the unit’s screen in a birds-eye view.

When reading the image you will see your boat in the middle of the screen and at the top. Anything down from your boat is what you have already passed by. Anything from the center of the image to the left is on the left of the boat, and the same on the right.


In the middle of the screen will be a black space, and anglers often wonder what this is. This is where the side scan doesn’t reach, and is the area directly under your boat that down scan would pick up.

You will also see black areas to the side if the scan hits the shoreline.

Humminbird fish finders have some of the best screens in the industry.

Contour Mode

With contour mode engaged, your unit will have vertical lines depicting distance on either side of the middle where your boat is and this is adjusted to the range you have chosen.

If you see some structure or a fish, you can use the vertical lines to see how far on one side of the boat the structure is, then start fishing on it.

Breaking Down A Side Scan Image

Reading Side Imaging Screen
Reading Side Imaging Screen

Take a look at the example side scan image above, Here is what they all show you while you’re fishing.

  • A – this is the location that has been scanned most recently
  • B – this is the recent image that was scanned a minute or so ago
  • C – this is the bottom of the water, river, or sea directly below the boat (The black middle part of the screen)
  • D – this is the surface of the water (Middle part)
  • E – this is the bottom of the water to the left of the boat
  • F – this is the bottom of the water the right of the boat

You’ll also notice the black area around C & D, this is directly below your boat and the area a down scan would show but the side scan doesn’t reach. The deeper the depth the larger the black area will be.

The vertical lines are there to show what distance what parts of the image are from your boat.

How important is Side Imaging on a fish finder?

To be honest, no anglers NEED side imaging, no anglers really need a fish finder but they make life a bit easier and help you enjoy your hobby a bit more.

One can get by with just a down imaging unit which is much more affordable but being able to see what’s to the side of your boat has huge advantages.

With down and side scan in play, you can find fishy areas over a 500-600 ft area.

With just down scan, you’ll have to drive your boat up and down the entire area around 20-30 times to get a sonar picture of it, whereas with side scan, you only have to drive past once.

Pros & Cons of Side Imaging

Before you decide that you have to have some side imaging technology in your vessel, let’s first take a holistic view of what’s good and what’s bad about this technology.

The Pros

  • It scans to the side of your boat which you would otherwise not see on a fish finder
  • You can scan more water faster to find fishy areas
  • It provides are more detailed view of the water you’re fishing in

The Cons

  • It’s more expensive than normal down imaging
  • You don’t get a picture of what is directly under your boat
  • It only works at a slow boat speed of 3-5 knots
  • Not very effective in deep water over 300ft
  • Turning the boat creates a poor picture

Why does side imaging need slow speeds to work?

Moving Boat
Moving Boat

Fellow anglers, this is the key to having clear images from side scan. Your boat speed is limited by your chart speed settings and in order to get the best pictures you’re going to have to match your boat speed to the chart speed and here is why.

When your boat is moving faster or slower than the chart speed, the images become distorted and elongated, or shortened. For example, when you set your chart speed to 4 knots then you need to drive your boat at 4 knots to get the clearest view possible.

Max Chart Speed

Since the chart speed settings have a maximum of 5 knots in most cases, anglers can’t go faster than 5 knots if they want a good picture. This is a real problem for marlin fishermen who have to go 7-8 knots to catch this species of fish.

Why does turning my vessel affect my side imaging sonar picture?

The picture created by side scan is based on reflections of the sonar waves. If you’re not driving in a straight line then the reflections will skew and come from a different distance to give you a distorted picture.

This does limit how you drive around the water but if you don’t rely on it too much then it won’t be too big of a problem.

Why doesn’t side imaging work well in a depth of over 300ft?

The depth of water side imaging can show you is based on the distance the sonar waves can travel. A 400 kHz will be absorbed by the water after hitting 300ft of depth and thus will not show anything deeper than its maximum range which is usually 300ft, but it depends on the unit.

Between down imaging and side imaging, down imaging uses lower frequency sonar waves around the 80 kHz mark which can penetrate up to 2000ft deep.

Where do I mount a side imaging transducer?

Transducer Installations
Transducer Installations

You should mount your side imaging transducer either on your transom, under the Step of your vessel, on the side of or under the jack plate, or on your trolling motor.

The choice is yours really but the key is that the transducer sits level with the water pointing down vertical so that it gets an even coverage.

If you mount it squiff or not parallel to the water, all your sonar pictures will end up being distorted.

Is it worth getting Mega Imaging?

Mega imaging basically means your transducer can send out sonar wave frequencies of 1000 kHz, so a 1 MHz. This gives you the power to see an immense amount of detail at a close range, since the higher the wave frequency the shorter the distance it can travel.

With mega imaging you will be able to pinpoint individual fish around a structure and even tell their size.

It’s a pretty cool feature but if I see a fish I’ll cast towards it, like I’m sure most of you would, so I don’t always see the need for seeing this much detail.

Other anglers, particularly bass pros, would disagree with me though as they are after a trophy that could win them up to a million bucks in some cases.


As with most things in fishing, if you can afford the extra costs of Mega Imaging, then it’s a fun feature to have and it might catch you some more fish now and then, but it’s certainly not a must.

Is Side Imaging Right for You?

If you can afford the $300 or so it costs to have a side imaging fish finder, then it’s probably worth having, but only if you’re going to use it. If you fish once a month, then it might not be worth the investment, but if it’s every week and occasionally competitive, then go for it.

You’ll see more fish, and find them quicker in the water column too than you ever would with a standard down scan fish finder, but you will need to control your speed.

Scanning Out

Thanks for reading my article, I hope you found it useful. Deciding whether to get side imaging or not is a big decision and I hope you found all the info you need here.

Please share this article with your fishing buddies and if you need some more info on fish finders, check out my other articles about the best fish finders on the market.

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