Memory Card Question

Quality

Quality

Member
If I'm shooting full hd 1080p with a 64gb 95mb/s memory card, how many hours can I get worth of footage? And if I decide to shoot 4k 2160p.
 
Check the manual or website for the particular camera you're shooting with. Back in the day, we figured roughly 1GB/min for HD, but there are so many cameras and codecs and bit-rates, frame rates, etc. now, it's impossible to give a blanket estimate. My P2 Vari with a 64GB card can give me 70 mins @ 60P in DVCProHD or AVC100 or like 3 hours shooting 24P(23.98). My C300 will give me 82 mins on a 32GB card and my F55 is all over the map depending on frame rate, rez and codec.
 
Quality said:
If I'm shooting full hd 1080p with a 64gb 95mb/s memory card, how many hours can I get worth of footage? And if I decide to shoot 4k 2160p.
Click to expand...

You're making this way too complicated. The resolution, chroma subsampling, bit depth, card speed, aperture, etc., are all irrelevant. All you need is the camera's recording bit rate. The bit rate, in bits per second, is literally how much data, in bits, the camera records to the memory card every second. (Actually there will be some added on for audio and other overhead, but that will be relatively trivial.)

To get your memory card usage in useful numbers, convert megabits/second (Mb/s) into gigabytes/hour (Gb/h). And to do that, with a bit of a safety margin, just divide by 2. That's it.

Here's a little more detail so you can check my working. Starting from megabits per second: there are 8 bits in a byte, so first divide by 8 to get megabytes per second. There are 3600 seconds in an hour, so then multiply by 3600 to get per hour. Then divide by 1,000 to get gigabytes per hour. To do it all at once, just multiply megabits/second by 0.450 to get gigabytes/hour.

You need to allolw a little on top of this -- add on a gigabyte per hour for audio, or thereabouts, and remember that stated card capacities don't include the file system overhead. And allow a little safety margin. So multiply by 0.5 -- in other words, you can just halve the bitrate to get (approximate) gigabytes per hour.

So, if you were recording at 240 Mb/s, it would make sense to allow 120 gigabytes of storage per hour of video.

You haven't shared what bit rate you're using (the one and only thing that matters), so I can't tell you the answer for your case.
 
David W. Jones said:
There are also tools available like this one....
Click to expand...

... in case "divide by 2" is too complicated?

Besides, that tool is junk. My camera records H.264 1080p. I set that up in the tool, set the frame rate, and it tells me that I need 35 GB/hour. Which means my camera is recording at a bitrate of 78 Mb/s.

Whet the hell? The "tool" assumes that H.264 1080p can *ONLY* be recorded at 78 Mb/s????? That's complete garbage! It can be recorded at pretty much any bitrate -- you trade off bitrate for quality, that's the whole point. In fact my camera records at either 35 or 50 (your choice), not 78, and uses either 17 or 23 GB/hour, not 35.

Basically the premise of the tool is dumb -- it can't possibly know what bitrate my camera is set to, unless it asks me, and it doesn't!
 
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