Buying

Borescope specs, decoded: which numbers actually matter

Inside the sharp band

Too close

By Andre Gaz, developer of InspectCam™ · Published 1 August 2026 · Last updated 16 October 2026

Open any borescope listing and you get a wall of numbers. 1080P. 5.0 megapixels. IP67. Eight adjustable LEDs. 16.5 feet of semi-rigid cable. Six adjustable brightness levels.

Most of it doesn't predict whether you'll be able to read a part number stamped on a block. One number does, and it's usually buried three-quarters of the way down the spec table — if it's there at all.

Focal distance (or "focal length"): the one that matters

Listings use both words. "Focal length 1 cm" and "focal distance 3–8 cm" describe the same thing on a borescope: how far from the tip the picture is sharp. It is not the optical focal length of the lens, which a listing almost never gives.

Nearly every borescope under a couple of hundred pounds or dollars has fixed focus. There is no autofocus, no manual focus ring, nothing to adjust. The lens is glued at one distance and everything sharp lives in a narrow band around it.

That band is typically something like 3 to 8 centimetres. Inside it, detail is crisp. Outside it, closer or further, the picture goes soft, and no amount of light or resolution rescues it.

This is why people buy a "5 megapixel 1080P" scope and get mush. The sensor was never the problem. They were holding the lens two centimetres from the thing they wanted to see, which is closer than the optics can resolve.

A few scopes have adjustable focus, usually a rotating collar behind the lens. If your work covers a wide range of distances, that's worth paying for far more than extra megapixels are.

Resolution, and the "1920P" problem

Here's a real listing, and it's not unusual. The product title says 1920P HD. The specification table on the same page says the sensor is 1280 × 720.

Two separate things are going on, and both are worth recognising.

First, 1920P is not a format. The "p" in 1080p refers to 1080 horizontal lines scanned progressively. Someone has taken the width of a 1080p frame (1920 pixels) and bolted a P on the end, because a bigger number sells. There is no 1920P standard, and any listing using it is telling you something about the seller.

Second, that scope has a 720p sensor. The 1920 × 1080 stills it advertises are interpolated: software stretches a smaller image up to a bigger pixel count. You get a larger file. You do not get more detail. Nothing is recovered that the sensor never captured.

Megapixel counts get the same treatment. "5.0MP" on a probe 5.5 mm across is arithmetic performed after the fact, not silicon. The sensors in these things are tiny (a few millimetres square) and physics puts a hard ceiling on what a lens that size can resolve, whatever the marketing says.

What to actually do: ignore the headline and find the native sensor resolution in the spec table. If the page won't tell you, assume it's the lowest number mentioned anywhere. And bear in mind that 720p, genuinely delivered and correctly focused, looks considerably better than fake 1080p.

Probe diameter: the real trade-off

This is the only spec where you're making a genuine engineering choice rather than being sold a number.

Common sizes are around 3.9 mm, 5.5 mm and 8 mm. Smaller fits through smaller holes — obviously — but you pay for it twice. A narrower probe carries a smaller lens and sensor, so image quality drops. It also carries fewer or dimmer LEDs, so you get less light exactly where you have least room for it.

• 8 mm. Best picture, most light, won't fit through a spark plug hole or a small drilled inspection hole.
• 5.5 mm. The common compromise, and the right default if you don't have a specific hole in mind.
• 3.9 mm and below. Buy this only if you know you need it. The pictures are noticeably worse, and you'll notice every time.

Measure the tightest access you actually deal with, then choose the largest probe that clears it. People routinely buy the smallest available on the assumption that smaller is more capable, then wonder why the image looks worse than the reviews suggested.

Dual lens: when a side camera is worth it

A dual-lens scope has a second camera on the side of the tip as well as the one facing forward. The forward camera shows where the probe is going; the side camera shows the wall beside it. That matters inside a pipe, a cylinder or a duct, where the thing you want to see is on the wall rather than straight ahead.

Check one thing before paying for it: how you switch between the two. If there's a button on the handle, the scope behaves the same in any app. If the switch exists only inside the maker's app, you're tied to that app, which matters if it stops being updated (more on proprietary scopes).

Quick reference table

What IP67 does and doesn't cover

IP ratings come from an international standard, and the two digits mean specific things. In IP67, the 6 means dust-tight and the 7 means it survives immersion in a metre of water for thirty minutes. IP68 means immersion deeper or longer, to whatever depth the manufacturer specifies. IP68 alone is not a number.

The catch is scope: the rating almost always applies to the probe and cable, not the handle, screen or transmitter. Listings rarely spell this out, and the photography usually implies the whole thing is submersible.

Practically, that means you can put the business end down a drain or into a flooded bilge. Dropping the handset in after it is a different outcome. If you genuinely need the whole tool waterproof, look for a rating stated separately for the handle, and if it isn't stated, it isn't rated.

Cable type and length

Two kinds, and the difference matters more than the length.

Semi-rigid holds whatever shape you bend it into. You can put a hook in the last few inches and steer the tip round a corner, or push it upward against gravity. For anything you're feeding into a cavity or up behind a panel, this is what you want.

Fully flexible goes where gravity takes it. Fine for dropping straight down a pipe or a wall void, useless for anything requiring aim.

On length: more is not better. Ten metres of cable is ten metres of stuff to manage on your knees in a crawlspace, and the further the tip is from your hands the less control you have over where it points. Most domestic and automotive work is comfortable with one to three metres. Buy long only if you have a specific long run in mind.

What isn't on the spec sheet

The specs describe the hardware. Whether you get a usable picture also depends on things no listing mentions.

Whether it's a standard UVC device. A USB scope that follows the USB Video Class standard can work with Android viewer apps that support it; in InspectCam™ only the Klein Tools ET16 is tested. One using a proprietary protocol only ever works with the maker's own app, and in this category those apps are frequently abandoned. Listings that say "driver-free" or "works with any camera app" are usually telling the truth. Ones that name a single required app are worth a closer look.

Whether the app is still maintained. Check the last-updated date before you buy, not after. A scope whose only software stopped being updated years ago is a scope with a shelf life, and Android and iOS both keep moving.

What happens on iPhone. Standard USB borescopes don't work on iPhone, whatever the box says: Apple documents external USB camera support for iPads with USB-C only. If you're an iPhone owner, that narrows your options to Wi-Fi scopes, or wired ones sold specifically for iPhone that work only in their maker's app, before any other spec matters. The detail, with Apple's own wording.

Questions people ask

What resolution do I actually need in a borescope?

Genuine 720p, correctly focused, is enough for most inspection work. Focus matters far more than pixel count: a sharp 720p image beats a soft 1080p one every time. Check the native sensor resolution in the spec table rather than the headline figure, which is often interpolated.

Is a 5 megapixel borescope better than a 2 megapixel one?

Usually not in any way you'd notice. Megapixel figures on cheap scopes are typically calculated by upscaling rather than captured by the sensor, and a lens a few millimetres across has hard physical limits regardless. Compare focal distance and probe diameter instead.

What does "1920P" mean on a borescope listing?

Nothing. It isn't a real format. The "p" in 1080p refers to 1080 horizontal lines; 1920 is the width of that frame. A listing advertising 1920P has taken the larger number for effect, and its sensor is frequently 720p.

Should I get a 5.5mm or 8mm borescope?

8 mm gives a better picture and more light; 5.5 mm fits through smaller openings. Measure the tightest access you actually work with and choose the largest probe that clears it. Going smaller than you need costs image quality and illumination for nothing.

Does IP67 mean the whole borescope is waterproof?

Almost never. The rating normally covers the probe and cable, not the handle, screen or Wi-Fi transmitter. IP67 itself means dust-tight and able to survive a metre of water for thirty minutes. If a listing doesn't rate the handle separately, assume it isn't rated.

Semi-rigid or flexible cable: which is better?

Semi-rigid for most work, because it holds a bend and lets you steer the tip round corners or push upward. Fully flexible is only preferable when you're dropping the probe straight down and want it to follow the shape of the space.

What does "focal length 1 cm" mean on a borescope?

It means the picture is sharpest about 1 cm from the tip. On borescope listings "focal length" and "focal distance" both describe where the image is in focus, not the optical focal length of the lens. Closer or further than that band, the image softens, because most cheap scopes have fixed focus.

Is a dual-lens borescope worth it?

If you're looking at the walls of a pipe, cylinder or duct, yes: the side camera shows the wall directly instead of at a steep angle. For looking straight into a gap it adds little. Check whether you switch lenses on the handle or only inside the maker's app, because the second ties you to that app.

We don't recommend specific models here, because we only list hardware we've tested. See how that works. If a spec on your scope behaves differently from what's described above, tell us.