3G vs 6G vs 12G SDI: What's the Difference and When to Use Each

If you've spec'd a multi-camera shoot, a PTZ studio, or any kind of live production lately, you've run into the alphabet soup of SDI standards: 3G, 6G, 12G. They look similar, the cables look identical, and the connectors are the same BNC — but using the wrong one is how you end up with a dropped 4K signal or a picture that won't sync. Here's what actually separates them, and when each one matters.

We've been wiring professional video and broadcast systems for over 45 years, including modern 4K PTZ studio installs. This is the practical breakdown.

What SDI Is

SDI (Serial Digital Interface) is the professional standard for carrying uncompressed digital video over coaxial cable with BNC connectors. Unlike HDMI, it locks securely, runs long distances, and is built for the demands of broadcast and live production. The number in front — 3G, 6G, 12G — refers to how much data the cable carries per second, measured in gigabits.

The Bandwidth Ladder

Each SDI tier roughly doubles the data rate of the one before it, and that bandwidth is what determines the resolution and frame rate it can carry on a single cable:

HD-SDI (1.5G) — 1.485 Gbps. Carries 1080i and 720p. The workhorse of HD broadcast for years.

3G-SDI — 2.97 Gbps. Carries full 1080p at up to 60fps on a single cable. This is still the most common standard for HD production.

6G-SDI — 6 Gbps. Carries single-cable UHD/4K at 30fps.

12G-SDI — 12 Gbps. Carries single-cable UHD/4K at 60fps — the current standard for 4K live production.

The 4K Problem 12G Solved

Before 6G and 12G existed, getting 4K over SDI meant quad-link — running four separate 3G-SDI cables to carry one 4K signal, then recombining them at the other end. It worked, but it was four times the cable, four times the connections, and four times the things that could go wrong. 12G-SDI carries that same 4K60 signal on a single cable, which is why it became the standard for modern 4K switchers, cameras, and PTZ systems. If you're building 4K infrastructure today, single-link 12G is almost always the right call over quad-link 3G.

Backward Compatibility

Here's the good news: the standards are backward compatible in the sense that a 12G-rated cable will happily carry a 3G or 6G signal. A 12G cable is electrically a higher-performance coax, so it handles everything below it. The reverse is not reliable — a cheap cable rated only for 3G may not cleanly pass a 12G signal, especially over any real distance. This is why many productions simply standardize on 12G-rated cable for everything: it future-proofs the run and removes the guesswork.

What It Costs

SDI cable cost scales with rating and length. A short factory-made 3G BNC patch cable runs about $10 to $30. The same length in certified 12G-rated cable costs more — often roughly double — because it requires tighter manufacturing tolerances and better shielding to pass 12 Gbps cleanly. For permanent installs, bulk coax (such as premium 4K-rated Belden) plus crimped BNC connectors is more economical per foot, but 12G-grade bulk coax and connectors still carry a premium over standard HD coax. The practical takeaway: the cable itself is rarely the expensive part of a production — so buying 12G-rated cable to avoid signal problems is cheap insurance compared to a failed shoot.

When to Use Each

For 1080p HD work — most corporate, event, and interview production — 3G-SDI is perfectly sufficient and the most cost-effective. Step up to 6G or 12G-SDI when you're shooting or switching 4K, building a 4K PTZ or studio system, or future-proofing a permanent install. In practice, for any new 4K infrastructure, 12G is the standard to build around because it handles 4K60 on a single cable and remains compatible with everything below it.

For systems where cable runs get long, the choice of standard also affects how far you can go before the signal degrades — a critical detail we cover in our companion post on SDI cable distances by resolution.

If you're planning a multi-camera, 4K, or PTZ system and want it wired right the first time, talk to us — we design and install this kind of infrastructure.

From Mr. Camera. Las Vegas video production since 1981.