Canon T5i (700D) Raw video Camera write speed too slow?

[dutchbushcraft]

Hello everyone,

I am sorry to ask this without proper introduction. I am new to filming with DSLR's but wanted to up my quality of my videos.
I bought a sandisk extreme 64gb classified as 90mbs write and 95mbs read. http://www.dataio.nl/sandisk-64gb-sdxc-extreme-pro-uhs-i-95mbs/?gclid=CjwKEAjwp-S6BRDj4Z7z2IWUhG8SJAAbqbF3Jis3FdTYesgJzLxo5Agm9qo3zn_g2hiY9TsvTocHpBoCto_w_wcB

The 700d predicts that I would write 80mbs with raw video on 24fps. However as soon as I start recording after a second or 3 it starts skipping massive amounts of frames. I did a speed test on my  pc using crystal disk mark. I get exactly 90mbs / 95mbs as advertised. However, the benchmark on the canon 700D maxed out at 37mbs. What am I doing wrong here? Does the card need to be formatted in a certain way to achieve max write speeds with the canon?

Thanks for your help!

[Walter Schulz]

SD-card interface in 700D is limited to about 41 MByte/s in write mode. 720p24 should be no problem. Anything beyond is not expected to record continuously.

[dutchbushcraft]

thanks for the reply mate! will try.

[wesley426]

Hello, I'm using the same camera… I'm wondering if you have posted your workflow/settings anywhere… Thanks for sharing if you have. I was not able to get the raw video working very well… I would experience dropped frames on anything past 12.5 frames per second… So right now I'm just using the dual ISO HDR video module instead… Thanks for sharing any ideas or suggestions.

[Walter Schulz]

1. Benchmark your card.
- Modules tab -> Bench.mo ON
- Restart cam, photo mode
- Overlay tab -> Global Draw OFF
- Debug tab -> Benchmarks -> Card Benchmarks -> Quick R/W benchmark (1 min)
 
Fast cards should pass 40 MByte/s writing.

2. Check RAW resolutions settings.
Don't expect 40 MByte/s recording continuously. 1) just tells you how the card is doing with the least amount of overhead. Doing RAW recording adds some overhead and the closer you get to the edge ...

3. Using ExFAT file system is mandatory. If you're using cards with 32 MByte or below you have to format cards with your cardreader and avoid reformatting in cam.

Load only modules needed for the task at hand. Don't use overlays.

[wesley426]

Walter; thanks for the tips....  I'll reformat with exfat and try the test again as my fat32 card is only getting 15mb write speed and 40ish read speed.

If I'm limited to 720p wouldn't the hdr video option with dual iso at 1080 be a better choice? How many stops of dynamic range would I lose with the hdr video option vs raw video?

Thanks for any further advice suggestions!

[Walter Schulz]

Benchmark test won't differ for FAT32 and ExFAT. Get a decent card.

[wesley426]

Thanks, for the tips...

I formatted exfat on my 32G PNY Turbo Performance micro sd card.... results:
Write speed: 39.4 MB/s
Read speed: 43.3 MB/s
Write speed: 39.6 MB/s
Read speed: 43.3 MB/s

Nightly.2016Jul09.700D114

I'll try recording more RAW now Still not sure if HDR Video at 1080p would be a better choice than RAW Video at 720p.

Wes

[Shartnado]

Guys, my apologies for resurrecting this old thread, but it's tuned in to something I'm trying to discover.

All of this discussion is pertaining to maximizing write speed to the SD card. What happens if I bypass the SD card and just stream live HDMI out to an external recorder that's fast enough to handle all the data? Is this not optimal? I know the external recorders are more expensive, but if you're looking to record RAW video, you're going to need to buy a lot of SD cards. Why not just use an external recorder?

[eNnvi]

http://magiclantern.wikia.com/wiki/HDMI_Output
This shoulder answer your question

Only few camera models have ckean hdmi 1080p in 4:2:2 and are anyway limited to 8bpcc

Ml raw allows to have 14 bppc and it's raw. Real raw, not HDMI recorded prores

With 10-12bit we're making big steps anyway