Recording · Practical guide

GH6: card-speed recording stops and dual-slot backup

When a GH6 stops recording a take, save the message and settings before changing cards. This guide covers SD and CFexpress: choosing media, preserving footage after an error and checking what each slot does. SSD recording has a separate guide.

A recording stop needs more detail than “4K 10-bit”

Before changing a card, record the warning text, DC-GH6 firmware, Rec. File Format, Rec Quality, bitrate, frame rate and slot. Include the card brand, product code, capacity, Video Speed Class and time until recording stopped. For an interview or conference, also note how long the camera had already been running: a short take immediately after power-on does not represent the entire session.

“4K 10-bit” does not identify the bitrate or compression. Check the complete setting before deciding whether the card meets the requirement for that recording.

The Japanese Lexar 1667x SILVER page specifies V60 and read speeds up to 250 MB/s. The Spanish page for the same family displays a V90 label that contradicts that description. Given this difference, verify the printed class and your card’s exact product code with Lexar before using it for a format that requires V90; the family name does not resolve the contradiction.

Choose the card by format and speed class, using the correct units

Consult Memory Cards That Can Be Used, DC-GH6 DVQP2441. The table summarizes minimum requirements by bitrate for video supported on SD; first check that the format can be recorded there. The manual excludes Apple ProRes at 4K or above, MOV at 800 Mbps or above, and VFR with ALL-Intra from SD recording.

Speed classes specify minimum sequential write speeds under the standard’s conditions. V60 and V90 use UHS-II or higher; a maximum read-speed figure does not identify that class. To compare units, 400 Mbps ÷ 8 = 50 MB/s. That calculation helps interpret a specification, but it does not replace the GH6’s V60 requirement or its format restrictions.

The Panasonic list dated February 9, 2024 identifies product codes and capacities and asks users to test the intended settings. It confirms basic operation without guaranteeing every operation. The base manual lists capacities as of January 2022; for a later card, also check the compatibility list and its notes. Do not reject or approve a card solely on that older table.

Choose the card by format and speed class, using the correct units
Bitrate of video supported on SD	Class specified by GH6	What to check
Up to 72 Mbps	Class 10, U1 or higher, or V10 or higher	Format and corresponding symbol.
Above 72 and up to 200 Mbps	U3 or V30 or higher	Class, product code and capacity.
Above 200 and up to 400 Mbps	V60 or higher	UHS-II interface and format.
Above 400 and up to 600 Mbps	V90	Format and model requirements.
Above 600 Mbps or a format excluded from SD	SD does not support that recording	CFexpress; SSD has its own procedure.

A hot CFexpress card and a faulty file need different checks

Message Displays links the speed warning to recording requirements; if those are met, it considers a drop in write speed. For CFexpress, it also says write speed may fall as the card heats up and asks users to wait for it to cool. Record the warning before attributing it to temperature: that possible mechanism does not identify the cause of every recording stop.

Review a copy of the clip in another player or editor and note whether it fails at the same times. Then, using media designated for testing and with previous files preserved, compare one variable at a time. Keep a record of format, duration and media usage. A short successful test with another card helps narrow the problem; it does not prove which component failed or validate a full day’s recording.

If a temperature warning appears, follow the camera’s procedure and stop the test. The temperature and HDMI guide explains what to record for signal paths sharing that GH6.

“Format this card?”: separate preserving footage from preparing the card

If footage still needs to be preserved, do not confirm formatting. For Memory Card Error/Format this card?, Panasonic offers using another card or copying the data before formatting. For Read Error/Write Error, it says to turn the camera off, reinsert the card and turn it on; it also considers a damaged card. If Now writing appears, wait for writing to finish and switch off before removing the card.

A displayed capacity or a card appearing in Disk Utility does not prove that the video is intact. Verify the files you were able to copy before considering the takes recovered; if they cannot be read, preserve the medium without continuing to write to it.

The 2023 Angelbird datasheet identifies AVP512CFXBSE, a 512 GB CFexpress 2.0 Type B card, with a maximum write speed of 850 MB/s and a stated sustained write speed of 800 MB/s. Those figures come from its internal tests and can vary with the system. Specifications for a v4 version do not apply to that unit.

The Angelbird manual published for that product, revision 20260703, calls for data backup and safe ejection. Remove the card with inaccessible footage from circulation and consult support before running repairs that write to it. If a .mdt file exists, separately review the scope of GH6 file repair.

Camera formatting and Low Level Format, after preserving the data

Card Format erases data: verify the copy before preparing the medium. Choose slot 1 CFexpress or slot 2 SD. For CFexpress, DISP. lets you select Low Level Format and confirm Yes; the manual recommends it when write speed has dropped. Do not switch off or operate other controls during the process.

The compatibility list also calls for physical formatting when first using CFexpress in GH6 and when write speed drops. These instructions prepare a card whose data has already been preserved; they do not recover an inaccessible card. These Low Level Format instructions apply to CFexpress, not SD or SSD.

After preparing the test medium, record at the intended quality and duration, then review a copy. Note what changed and whether the message reappears. If it persists, keep that record for support; repeated formatting does not demonstrate a repair.

Two slots: check whether you selected relay, backup or allocation

Check Double Card Slot Function with the selected format. The format must support SD; video Backup excludes SD/SDHC paired with CFexpress and excludes Loop Recording. Use the compatible SDXC combination. Panasonic recommends equal capacities: if speed class or capacity is insufficient, both recordings stop.

For the test, note the mode and record a sample in the agreed format. Copy each card into a folder identified by slot and review both files: duration, beginning/end, picture and speech channels. Keep a record of what you checked; two inserted cards do not establish two usable recordings.

Backup Rec shares the camera and power supply. If the session must continue after a camera stops, define another capture path, its dependencies and the person responsible in the session plan. The card worksheet separates the proposed test, actual result and files reviewed.

Two slots: check whether you selected relay, backup or allocation
Mode	Purpose	Suggested check before the event
Relay Rec	Continue when the first card fills	Identify destinations and check files from both parts.
Backup Rec	Record simultaneously to both cards	Verify compatibility and open each copy.
Allocation Rec	Choose destinations by file type	Confirm Video Destination and check where the clip was saved.

Frequently asked questions

Does GH6 need V90 for every 4K 10-bit video format?

Resolution and bit depth are not enough. For video supported on SD, GH6 requires V60 or higher above 200 and up to 400 Mbps, and V90 above 400 and up to 600 Mbps. Check Rec Quality and the format exclusions in the table.

Does a printed speed of 250 MB/s prove sufficient continuous write performance?

Check whether the figure describes reading, maximum writing or sustained writing. Also record the Video Speed Class and product code. Converting Mbps to MB/s does not enable a format that GH6 excludes from SD.

Does a card on Panasonic’s list guarantee an entire session?

The list states basic operation and calls for a test with the intended settings. Find the row for the product code and capacity, read its notes and record the duration and file you actually reviewed.

Does the speed warning confirm that the CFexpress card overheated?

The manual considers that possibility, but the message also requires checking the recording requirements. Keep the warning, format and time; wait for cooling when appropriate and compare outside the session without deliberately forcing a recording stop.

What should I do if GH6 shows “Format this card?” and I need the footage?

Do not confirm erasure. Set aside the card containing footage that still needs preservation, record the attempts and consult support if you cannot preserve the data. Preparing media and recovering files require different decisions.

Does Low Level Format recover files from a CFexpress card?

It erases the contents. Panasonic specifies it for preparation and reduced write speed, after preserving the data. Do not use it as recovery or apply those instructions to SD or SSD.

Does Relay Rec put the same video on both GH6 cards?

Relay switches to the other card when the first fills. For simultaneous copies, check Backup Rec and its compatibility; the function does not operate with settings unsupported on SD.

Does Backup Rec continue on CFexpress if the SD card lacks the required speed class or capacity?

The manual says both recordings stop. Prepare compatible media and check the files before the event. To cover a camera stopping, plan another capture path and review its dependencies.