Railfan Technology > Scan disk capacity and speed

OK, I have done a search and found nothing.

I know how disks are listed for capacity, but I have heard they have different srecording speeds and so I am wondering how one knows what is fast and what is slow,

Comments????

Rob

They do have different speeds, but it's not a single number. Rotational speed is the most commonly quoted. 5400 RPM is slow-ish: these disks is made for high capacity, or on the cheap. 7200 RPM is the "performance" model, at least for ordinary people. 10,000 RPM is the fastest, for use mostly in "enterprise" machines, and may cost significantly more.

This doesn't cover Solid State Drives (SSDs). They are generally more expensive than hard disks, but are somewhere between faster and "a lot faster," depending on the workload. I think over half of all notebook computers sold now have SSDs rather than hard drives.

im having trouble posting links for some reason, but search "the numbers on your memory card."  Look for the article from B and H Photo and Video.  

John

OregonOldGuy Wrote:
-------------------------------------------------------
> OK, I have done a search and found nothing.
>
> I know how disks are listed for capacity, but I
> have heard they have different srecording speeds
> and so I am wondering how one knows what is fast
> and what is slow,
>
> Comments????
>
> Rob

Rob are you referring to the really small little flat disks that go into cameras and such or are you talking about 2.5" wide "hard drives" or are you talking about USB "sticks"?

Hadn't checked this in far too long.  I'm referring to the flat SDHC cards that go into camera body's.  One I have do have something marked as 80MB/s.  Next one, no. I didn't dig out rest.  Really only becomes an issue about once a year when I push one a bit hard.

Rob

I know very little about the technical details, but but apparently the more expensive cards read a lot faster.  When I first got into digital I bought cheaper cards, and I noticed that if I shot in various burst modes after one or two quick exposures the camera would slow down and go click wait click wait click wait and so on.  As best as I could figure out the camera's internal memory (buffer) was filling up and waiting for the slow chip to download the files to make room for the next image, that was what each little wait was all about.  When I bought a more expensive faster reading card this problem immediately went away.  I am guessing the message here is that if you generally do one exposure at a time, a cheap slow SD card may be just fine.  But if you do a lot of bracketing or rapid bursts, you may want a more expensive faster card.

JBWX



Edited 1 time(s). Last edit at 09/27/19 09:33 by jbwest.

It's write speed (not read speed), but yes, the camera buffers the data. SD cards are typically 10-30 MB/second. The raw images from my SLR (Canon 7D, crop sensor) are about 25 MB, so a "3U" SD card can accept 1 frame per second, and the camera can shoot at about 8 fps. The camera buffer holds about 25 pictures (3 seconds of high-speed shooting), but then it should take about 25 seconds to write that to the SD card. You can buy SD cards up to about 90 MB/sec, which should write those 25 pictures in about 8 seconds.

The fastest CF cards still beat the fastest SD cards by a bit (theoretical 150 MB/s and 110 MB/sec in practice), not to mention that CFs are easier to find when they fall into the sofa.



Edited 2 time(s). Last edit at 09/28/19 21:06 by clem.