CCTV spec sheet mathwhat matters (and what doesn’t)
Megapixels sell cameras. Sensors, lenses, and bitrate determine whether you can actually identify a face or plate in real lighting.
The 10‑second rule
Don't buy "the highest MP". Buy the right lens + sensor for your distance and lighting, then make sure your recorder/storage can keep up.
What this guide gives you
- How to read the specs that actually affect usable footage
- Where marketing routinely hides the constraints (bitrate, processing, sensor size)
- A simple way to match lens + distance, and avoid buying the wrong "MP"
- A storage sizing mindset that doesn't rely on wishful thinking
By the Doberman install team · CCTV system designers & installers, Leicester · Last reviewed January 2026
By the Doberman install team
CCTV system designers & installers, Leicester
Last reviewed January 2026
What spec sheets don't tell you (but your footage will)
Spec sheets are designed to be compared quickly - which is exactly why they can mislead. After reviewing footage across residential and small business installs, we've found the most important factors are either missing from the spec sheet entirely or buried in marketing.
- Compression and processing: aggressive noise reduction can make faces look "painted", and heavy compression can smear motion.
- Bitrate caps: some systems throttle bitrate to save bandwidth/storage. The camera may be capable of more than you ever get.
- Shutter behaviour in low light: to brighten the image, cameras may slow shutter speed - which increases motion blur.
- Real WDR performance: "WDR" on a spec sheet doesn't guarantee usable faces in backlit scenes.
That's why the goal isn't "best specs". The goal is correct specs for your distances, lighting, and recording model.
The cheat sheet (what to look at first)
Megapixels (MP)
MP is resolution - not clarity. More pixels can mean worse low‑light if the sensor is small or the bitrate is constrained.
Use MP to match the scene (wide vs tight), not as a quality badge.
Sensor size (often hidden)
Bigger sensor generally = better low‑light and dynamic range. If a camera looks sharp in daylight but mushy at night, this is often why.
Lens (mm) and field of view
Wider lens (smaller mm) covers more but spreads pixels thinner. Narrower lens (larger mm) gives more detail at a distance.
Lens choice is often the biggest practical difference between "I can see someone" and "I can identify them".
WDR / HDR
Look for good WDR when you have backlit scenes (doors, shopfronts, windows). It's the difference between "white blob" and a usable face.
IR / night performance
IR range marketing is optimistic. Real performance depends on placement, reflections, and whether there's any ambient light.
Watch out for IR reflecting off soffits/walls close to the camera - it can wash out the image and reduce usable detail.
Bitrate + storage (the unsexy part)
If the recorder can't store the bitrate, you get smeary motion and missed details. Storage also determines how many days you can retain footage.
When footage looks "fine" when still but falls apart on movement, bitrate is often the reason.
Lens + distance: the quickest way to stop buying the wrong camera
Most "bad camera" installs are really "wrong lens for the distance" installs. A wide lens can show a whole driveway, but it can also turn a person at the gate into a tiny blob.
Use this as a rule-of-thumb. It won't replace a proper design, but it will stop you making the most common mistake.
| Lens | Typical use | Trade-off | Watch-outs |
|---|---|---|---|
| Wide (≈2.8mm) | Covering a wide area (front garden, shop floor overview) | More coverage, less detail at distance | Faces/plates at the far end can become "small on screen" |
| Medium (≈4mm) | Balanced coverage (door + driveway, typical entrances) | Good compromise for many installs | Still needs correct placement to avoid angles that hide faces |
| Narrow (≈6-12mm) | Detail at distance (gates, long driveways, specific choke points) | Less coverage, higher detail where it points | Easy to aim wrong and miss context outside the frame |
Wide (≈2.8mm)
- Typical use
- Covering a wide area (front garden, shop floor overview)
- Trade-off
- More coverage, less detail at distance
- Watch-outs
- Faces/plates at the far end can become "small on screen"
Medium (≈4mm)
- Typical use
- Balanced coverage (door + driveway, typical entrances)
- Trade-off
- Good compromise for many installs
- Watch-outs
- Still needs correct placement to avoid angles that hide faces
Narrow (≈6-12mm)
- Typical use
- Detail at distance (gates, long driveways, specific choke points)
- Trade-off
- Less coverage, higher detail where it points
- Watch-outs
- Easy to aim wrong and miss context outside the frame
If you're not sure whether you need wide coverage or detail at distance, decide your priority first: overview vs identification. In many cases you use a mix: a wide overview plus a tighter "choke point" camera.
Low light: why "more MP" can look worse at night
Low light is where CCTV either becomes genuinely useful or becomes a blurry suggestion of what happened. Marketing tends to push megapixels because it's easy to understand, but low light performance is more about how much light the camera can gather and how it processes that signal.
- Sensor size: larger sensors generally handle noise better and keep more usable detail.
- Lens/aperture: affects how much light hits the sensor. (Often not highlighted in marketing.)
- Bitrate: if bitrate is too low, low-light footage collapses into mush during movement.
If you care about night footage, avoid optimising for daytime sharpness alone. The goal is usable detail in the conditions that matter.
WDR: when it matters (and what "good" looks like)
WDR matters when you have bright highlights and deep shadows in the same frame - think doors, windows, shopfronts, and garages with daylight behind them.
"Good WDR" means you can still see facial detail in the shadowed area without blowing out the background into a white sheet.
IR pitfalls: reflections, spiders, and overexposure
IR is useful, but it creates its own problems. These are the IR issues we fix most often on site - and they almost always come down to placement, not hardware.
- Mounting too close to a wall or soffit can cause white fogging across the whole image. We see this regularly on under-soffit mounts where the camera sits less than 10cm from the ceiling.
- Spiders love warm cameras and can trigger constant motion alerts and block the view. It's one of the most common support calls we get in warmer months.
- Highly reflective number plates can bloom under IR if exposure is poorly tuned - the plate becomes an unreadable white rectangle.
A small change in placement can make a dramatic difference - which is why a site survey is more valuable than "bigger numbers" on a spec sheet.
Bitrate + storage: a simple sizing mindset
Storage planning feels boring until you need footage. The key is deciding your recording model first (continuous vs motion), then sizing storage so quality stays consistent.
Practical approach
- Decide how many days of retention you want.
- Decide whether you want continuous recording.
- Choose a sensible bitrate target (don't starve motion footage).
- Size storage to match, then add headroom.
If you're comparing PoE vs Wi‑Fi, storage tends to push you towards PoE because stable connectivity makes consistent bitrate easier to achieve. Start with: PoE vs Wi‑Fi comparison.
Worked example: front door + driveway
Here's how the spec sheet thinking applies to a typical install we'd design. The goal isn't to "max out specs". It's to select specs that match the job at each camera position.
- Door camera: prioritise WDR and a lens that captures faces at typical door distance.
- Driveway overview: prioritise wide coverage and stable recording; accept less detail at distance.
- Choke point (gate/entrance): use a tighter lens for identification at distance.
If you want this mapped to your actual layout, that's exactly what a quote/site survey is for - camera positions, lenses, and recorder/storage sized to your goals. See our home CCTV installation or business CCTV installation services for what a designed system includes.
Put it together: what to ask before you buy
- What distance do I need to identify someone at (front door, driveway, car park)?
- What's the lighting like (street light, pitch dark, strong backlight)?
- Do I need continuous recording, or only motion clips?
- How many days of retention do I want locally?
- Where will the cable runs go (clean install) and where will the recorder live?
If you're deciding between PoE and Wi‑Fi, start with: PoE vs Wi‑Fi guide.
About this guide
Who wrote this
This guide is written by the Doberman install team - CCTV system designers and installers working across residential and small business properties in Leicester. Every recommendation comes from hands-on experience with site surveys, system design, installation, and ongoing support.
How this guide was produced
The spec recommendations reflect patterns we've identified across real installs: footage reviews where detail was lost, support calls where night performance disappointed, and site surveys where the wrong lens was specified for the distance. Nothing here is based on manufacturer marketing or lab benchmarks.
Why we wrote it
Most buyers compare cameras by megapixels and price. That leads to systems that look sharp in a showroom demo but fail in real lighting at real distances. This guide exists to help you understand what actually affects usable footage - so you can ask better questions before you buy, regardless of which installer you choose.
Disclosure
Doberman designs and installs CCTV systems. We have a commercial interest in people choosing professional installation, and we're transparent about that. We've written this guide to be useful whether you choose us or not - we focus on specs that affect usable footage, not specs that look good in a comparison chart.
FAQ: CCTV spec sheets
Is "8MP" always better than "4MP"?
Not automatically. If the sensor is small or the bitrate is constrained, higher MP can mean more noise and more compression artefacts, especially in low light.
Why does night footage look smeary?
Low light forces longer exposure and more noise reduction. That's where sensor size, lens aperture, bitrate, and lighting matter more than a big MP number.
What's the difference between WDR and "HDR"?
Marketing varies, but the practical goal is the same: handle scenes with bright highlights and dark shadows so faces don't turn into silhouettes.
Do I need IR?
If areas are genuinely dark, yes - but IR also creates pitfalls (reflections, overexposure close to the camera). Placement matters.
How much storage do I need?
It depends on number of cameras, resolution/bitrate, and whether you record continuously. The right approach is to choose the recording model first, then size storage to match.