Author Topic: 5D Mk3 RAW 60FPS Skipping frames even with a fast CF card?!  (Read 4706 times)

tprloveridge

  • Just arrived
  • *
  • Posts: 1
I have 5d mk3 with magic lantern and the Raw module working on 30 fps with no skipping frames, but when i change the camera settings to 60 fps i seem to be having a lot of frames skipping.

I have a Lexar Pro 1000x 32GB CF card with a writing speed of 150mb/s. I thought this card would be fast enough to shoot 60fps?

I had selected 'Allow' in frame skipping and in a 5 second shot it said I had 160 skipped frames?! is that normal?

Any advice?

thanks

jimmyD30

  • Senior
  • ****
  • Posts: 386
Re: 5D Mk3 RAW 60FPS Skipping frames even with a fast CF card?!
« Reply #1 on: July 07, 2014, 01:52:53 PM »
The max write speed for 5DM3 is 100 MBps, this is a limitation of the camera, not the memory card.

Also, the read/write speeds of cards are always overrated and are rarely achieved in real world, plus for ML purpose you should run an in camera speed test and depend on those results, not what the card manufacturer states.

To determine if your shooting settings are feasible, you can do the math yourself... Each pixel is 1.75 bytes (14-bits) of data, you don't mention resolution, so I'll assume 1080p.

1920x1080x1.75 ≈ 3.6MB per frame x 24fps ≈ 86MBps (continuous possible with fast card)
1920x1080x1.75 ≈ 3.6MB per frame x 60fps ≈ 216MBps (continuous not possible, exceeds camera max write speed)

For simplicity sake the above calculations are approximate (but very close), hence the use of the approximation symbol '≈' ;)

Now you see the formula and can try any combination of resolution x frame rate and compare to the write speed determined for each card by in camera speed test.

chmee

  • Contributor
  • Hero Member
  • *****
  • Posts: 1031
  • raw2cdng
Re: 5D Mk3 RAW 60FPS Skipping frames even with a fast CF card?!
« Reply #2 on: July 07, 2014, 02:13:20 PM »
..every pixel is nearly two bytes. 14bit to be accurate.

Xres*Yres*14/8192 = KBytes per Frame
FPS*Xres*Yres*14/8192 = KBytes per Second.

Example:
24*1920*1080*14/8192 = 85.050 -> ~85MB/sec
60*1920*1080*14/8192 => 212MB/sec (computer says no)

regards chmee

jimmyD30

  • Senior
  • ****
  • Posts: 386
Re: 5D Mk3 RAW 60FPS Skipping frames even with a fast CF card?!
« Reply #3 on: July 07, 2014, 02:18:48 PM »
@chmee

Thank you! It's been a while since I've done these calculations, I'll update my post :)

legreve

  • New to the forum
  • *
  • Posts: 27
Re: 5D Mk3 RAW 60FPS Skipping frames even with a fast CF card?!
« Reply #4 on: October 04, 2014, 02:13:10 PM »
Last year around this time I shot a music video on 5D3 with ML raw... It was shot in 60fps with an aspect ratio of 1.85 and worked like a charm.

Back then the data requirement was 87mb or so and having around 92mb with my Komputerbay cards there were no issues.

But now I tried again with a march 17 and I couldnt get past 82.3
Also the info in ml says that now 107mb is needed.....? Well it wasnt last year.

What has happend?