Too often I hear and read about problems recording files, both photographic and video, associated with incredible technical bestiality, both because there is so much misinformation, and because they are often topics dealt with very superficially, which causes problems working.
The disturbing thing is that often even companies are not prepared to answer trivial questions, I still keep an email from the technical support of a well-known Company regarding the request for a list of SD certified for the registration of the 400mbits data stream of their room, they will have tested it somehow since they released the demonstration videos, but no one knew me to give list of certified cards to get such results , and I certainly don't spend hundreds of euros on useless cards to do the tests for them, as suggested by the assistance.
Why do I need to have fast support and what happens when I use more support than I need?
When we're taking a photograph, we're shooting a video, we're creating data that goes through 5 different possible bottlenecks:
- Room internal buffer size
- Camera recording controller (UHS-II fast card support or not)
- The external buffer size of the card (before writing to cells the controller often has a passing buffer to free the camera buffer)
- Card logging controller (cell management is done by a controller that records data directly or often compresses it to speed up the transfer).
- Quality cells that maintain the same writing speed for all cells, many supports after randomly filling half of the cells slow down because they have mapped the data badly and I have to "find the free spaces".
Since with the choice of the card we are influencing a large part of these elements of data write speed management, it is important to make the right choice, because if the chosen support is the optimal one we will have a number of advantages:
- recording at the highest quality of video
- recording at most bitrate of videos (not always coicide with the first point, but there are advantages and differences in this)
- recording longer frame bursts
- responsiveness of the machine to shoot again after taking the first frames
On the contrary, if the device is not adequate we may encounter the following problems:
- video duration limits at the highest quality/bitrate (depends on the internal buffer, normally a few seconds are spoken if the card is not adequate), it is expected because always the same interval.
- If the card is discreetly fast, we can have interruptions of video shooting after an X time (buffer that fills but we do not have feedback can be even after minutes of recording) unpredictable.
- longer wait times after snapping to wait for the buffer to be flushed
- flushing the burst buffer takes seconds and therefore you can't snap in the meantime
- short bursts because the camera buffer fills up immediately
how do I choose the right card?
The first limitation in card selection is that manufacturers often offer confusing and biased data to deceive the casual buyer by providing unclear or often unclear or often indicative acronyms and indications of only part of the data:
- SD Secure Digital up to 2gb
- SDHC Secure Digital High Capacity 4 to 32 gb
- SDXC Secure Digital eXtended Capacity from 64gb to 2 tb
- Class 2 writing at 2 mb/s
- Class 4 writing at 4 mb/s
- Class 6 writing at 6 mb/s
- Class 10 writing at 10 mb/s
- SD UHS Speed Class-I U1 write guaranteed at 10 mb/s for all board capacity
- SD UHS Speed Class-I U3 write guaranteed at 30 mb/s for all board capacity
- SD UHS Speed Class-II U1 and U3 write guaranteed from 150 mb/s to 312 for all board capacity
- SD Video Speed Class new category for video recording with V6 performance guarantee (6 mb/s), V10(10mb/s),V30 (30 mb/s), V60(60mb/s),V90 (90 mb/s)
Often when you see the speeds written on the cards we talk about the reading speeds, not the writing, which we are not interested in writing files in recovery.
Both are SDXC Class 10, U3
the first law at 95 mb/s but V30, then writes at 30 mb/s
the second law at 300 mb/s but writes up to 260mb/s.
So it's important to know how to read the acronyms, check the true writing speeds of SD cards to avoid surprises while working.
how do I choose the right ssd?
Today, several chambers use ssd for data recording, or through CF2 to Esata adapters transfer files to SSD. The same rules as SD cards also apply to CF and SSDs, indeed there are also more hidden dangers, because often the declared speeds are docca, that is, obtained only by hardware tricks, but only when they work on a computer, while when they are connected with a direct recording system these elements do not work.
Too many users overlook the fact that there are controllers, buffers, and often tricks to reach peak speeds that will never be maintained during continuous file recording.
Ssd producers often change the internal memories of ssd without changing the acronyms, so ssd discs tested last year contain different, less efficient, less rapid memories than those tested in the past.
In addition, depending on the controller, disk type, memory, speed can be constant while filling the disk, or while filling the disk, after half it can be less than 30% of the declared value.
Each disc is a story in its own right, the different sizes of a disc offer different performance because they change the controllers, the type of memory, and often also the way the discs are filled, so there can be inefficient 256 gb ssd, but the same 1 tera cut disc is perfectly usable and compatible with the highest writing speeds.
Obviously the ssd manufacturers test the ssd to use them in the computer and therefore it is not illegal to declare certain performance, because on computers they can reach 480 mb/s when in fact connected to a normal sata interface make at most 130/140 mb/s constant, because the rest of the performance are peaks obtained with data compression and transfer from one controller to another.
For these reasons, the lists of certified media are very short and limited to certain brands, discs, and particular sizes of these discs.
NEVER ASSUME OR TRUST TECHNICAL INDICATIONS
Always buy certified media from the parent company of the room, and/or check the support before a job with multiple footage, both with continuous shooting until you fill the disc, alternate footage, lights and camera shutdowns etc etc.
I had experiences of records that for declared speeds should have supported continuous raw recordings, when in fact they struggled with recordings in high quality DI formats because they were just peak speeds and nothing constant.