3G vs 6G vs 12G SDI: What's the Difference and Why Should You Care?

Somebody’s going to ask you this on set. Here’s how to answer without sounding like you’re reading a Wikipedia article out loud.

The quick version

3G-SDI handles 1080p60. It’s been the industry backbone for over a decade.

6G-SDI handles 4K30. The middle child nobody remembers. Showed up late, left early.

12G-SDI handles 4K60. The only one worth building around.

The numbers

Each one roughly doubles the last. More pixels times more frames equals more data. That’s the whole mystery.

A brief history

3G-SDI (2006 to present)

3G-SDI (SMPTE 424M) arrived when HD was becoming gospel. It gave us enough pipe to push 1080p at real frame rates over a single cable.

For most of the 2010s, that’s all anyone needed. Cameras shot 1080p. Monitors displayed 1080p. Recorders captured 1080p. The entire ecosystem agreed on one thing for once. Beautiful.

6G-SDI (~2015)

When 4K started making noise, 6G appeared like a temp worker. Technically capable of 4K at 30fps, but by the time anyone built infrastructure for it, 12G was already knocking on the door.

Most manufacturers took one look at 6G and said “nah, skip it.” You’ll see it referenced in some RED WEAPON specs and a few oddball devices, but nobody built a career around 6G-SDI. It’s the LaserDisc of signal standards.

12G-SDI (2015 to present)

12G-SDI (SMPTE ST 2082) does 4K at 60fps and above. One cable. No asterisks.

Every serious camera released in the last few years outputs 12G. Every serious monitor accepts it. This is the standard. Stop shopping.

Remember quad-link? Don’t.

Before 12G was ready, people got 4K over SDI by running quad-link 3G-SDI. Four separate cables, each carrying one quarter of the image, all synchronized.

It worked the way duct tape “works.” Four cables per signal. Four times the failure points. Mix up one cable and your image looks like a Picasso. 12G killed quad-link, and the industry exhaled.

What actually matters on set

If you’re just monitoring, 3G is fine. You’re sending picture to a 7-inch screen for focus and framing. Nobody’s pixel-peeping 4K on a monitor the size of a paperback book.

If you’re recording externally, match the camera’s output. 12G camera means 12G recorder means 12G cables. Anything less and you’re paying for resolution you’re throwing in the trash.

The classic hybrid setup: camera sends 12G to the recorder, recorder kicks out a 3G downconvert to your monitors. Full quality where it counts, monitoring where you need it.

If you’re feeding a truck or studio, this is where it gets real. Older trucks and studios are 3G soup to nuts. Newer ones are moving to 12G. Know before you show up. Showing up with the wrong cables to a broadcast truck is like showing up to a potluck with an empty plate.

Compatibility

12G cables work with everything. That bottom row is all green lights, which is the whole point.

The cost conversation

Yes, 12G cables cost a bit more than 3G. The price gap shrinks every year, you buy cables once if you buy right, you’re not scrambling when the camera upgrade lands, and you’re never the person on set mooching cables like it’s college.

How to handle the producer

When they push back on “expensive” cables:

“The camera outputs 12G. If we run 3G cables, we’re throwing away the resolution the client is paying for. On a job this size, the cable cost is a rounding error.”

That line has a 100% close rate.

Where things stand

3G-SDI is still everywhere, still useful, slowly getting pushed to the kids’ table. 6G-SDI was dead on arrival. Ignore it. 12G-SDI is the present and the future. Buy everything in this standard and stop thinking about it.