Silly MB/s question

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Archive 2009 · Silly MB/s question

DubiousDrewski
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p.1 #1 · Silly MB/s question

So a 14.7 MP camera, such as the upcoming K7, creates a 23.5MB RAW file. The K7 will shoot at 5.2 fps. This should create data at 122MB/s, shouldn't it? The fastest SD cards are rated at 30MB/s. This seems terribly inadequate.

So what's the deal? I'm missing something.

Jul 02, 2009 at 01:10 AM

wlescall
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p.1 #2 · Silly MB/s question

DubiousDrewski wrote:
So a 14.7 MP camera, such as the upcoming K7, creates a 23.5MB RAW file. The K7 will shoot at 5.2 fps. This should create data at 122MB/s, shouldn't it? The fastest SD cards are rated at 30MB/s. This seems terribly inadequate.

So what's the deal? I'm missing something.

The buffer memory in the camera itself.

Do the specs say how many shots at 5.2 fps? My 50D will shoot 16 RAW shots at 6.3 fps before I have to wait for the camera to dump the data to the card.

Jul 02, 2009 at 01:33 AM

DubiousDrewski
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p.1 #3 · Silly MB/s question

It can do 15 RAW files before stopping. On second thought, at 30MB/s, I suppose the camera only needs 4 seconds to dump a buffer that's filled with 122MB of data. Four seconds sounds about right.

Hmm. Maybe there's no issue here.

Although I wonder if an even faster SD card would offer any benefit at all (45MB/s? Yes please!). I wish camera manufacturers would publish the maximum write speed of their bodies. They just don't do it for some reason.

Jul 02, 2009 at 01:47 AM

EB-1
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p.1 #4 · Silly MB/s question

DubiousDrewski wrote:
So a 14.7 MP camera, such as the upcoming K7, creates a 23.5MB RAW file. The K7 will shoot at 5.2 fps. This should create data at 122MB/s, shouldn't it? The fastest SD cards are rated at 30MB/s. This seems terribly inadequate.

So what's the deal? I'm missing something.

That 14.7 MP file is compressed to create the RAW file. Image processing, compression, controller throughput, etc. limit write speed to less than the raw A/D conversion to buffer speed.

EBH

Jul 03, 2009 at 02:11 AM

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