Class 6 SDHC cards,

I'm finding it difficult to find benchmarks for Panasonic class 10, the best I could see were ones that use CHDK - the custom firmware for Canon powershot P&S cams - to check speeds.

CHDK wikia

From what I can see the class 10 equals or slightly beats the Sandisk Ultra2 - but and here is the dinger - it seems to have very poor performance on single 64K writes - 1/4 speed of other cards.

I wonder if the way the K7 writes video streams is hitting this overhead for small writes heavily?

Chris

Just tried a quick experiment with my K20. Set to raw+jpeg with the Sandisc extreme III class six, I can take 10-11 pictures on fast multiple exposure before the buffer fills up and it grinds to a standstill.

With a class 2 card it manages 6-7.

QED.

I just buy Sandisk Extreme IIIs and forget all about the technicalities - has done me alright so far

Great and since you don't talk about FPS I can assume that stays the same?

For the first few they are similar, but with the class 2 they taper off earlier.

with a sandisk extreme III you can shoot video as long as the card fills up. with other cards, (cant remember what class, but clearly lower, even if 8gb) i can only record 30-40 seconds of video.

No that's not true because you've a 4 GiB minus 1 byte file size limit because of the file system format, since we use FAT.

SDXC will come this spring and they get exFAT as standard but I wonder how well that is going to be support. exFAT has a file size limit of 64 ZiB (512 TiB recommended max) so we can use that for a long time
To be honest I've no idea why they didn't make the current models camera SDXC ready since then you could use exFAT also with SDHC cards and then you could really fill them up, which means your max film time is the card size limit.
Probably isn't really useful but it looks interesting in the specs.


ps. Gib, Tib, Zib seems to be the standard for binary these days, the "i" indicates that.
So:
GiB = GB
TiB = TB
ZiB = ZB

Hey stefan,

I have absolutely no idea what you are saying here. sorry, but I am really not on the same page

........sorry Stefan - completely lost me as well

Let me have a go......

The maximum video size in the K-7 is 4GB, so you can't necessarily keep shooting video until the card fills up if the card is bigger than 4GB. You get stopped once it's 4GB.

This limit comes from the maximum size of a file with the FAT32 system that the camera uses.

Stefan mentions some other file systems - that he wishes the camera would use - that allow files larger than 4GB.

Correct Peter, but this is in no way related to speed which was the original topic so his point is irrelevant.

Not relevant to the original topic, but Stefan's point was relevant (a correction) to Nathan's statement. It may be useful to anyone who didn't know about the 4GB limit.

as I said before, on my 8 GB INOV8, class 6, SDHC card, I can only record up to 30/40 seconds of video, and then it starts buffering, and shuts the video down.

On my Sandisk extreme III 4GB card, I can record all the 4GB, or until the card is full, without interrupting the recording.

Why does this happen in your opinion?

Thank you all

Yes that's correct you can fill card not larger then 4GB fully but you can only fill a 8GB card for the half because the the largest a file can be is 4GB on the standard format.
The file size limit is because of FAT32 like Pete says, exFAT has a file limit of 64 ZB (Zettabyte = 1 billion terabytes)

No Pete I don't wish that, exFAT really is the standard use for SDXC cards that will come this spring. link
SDXC is the card that comes after the SDHC in terms of size.
So it's like this:
SD = up to 2GB
SDHC = 4GB up to 32GB
SDXC = 64GB up to 2TB

Here are the SDXC standards on the official SD site link

Since the SDXC use a different file system exFAT as standard instead of FAT32 that means that a major upgrade is needed for cameras to support it also the only OS that support the format currently is Windows (XP, Vista & 7).
A solution is to format the SDXC card from exFAT to FAT32 but since the standard is exFAT that would probably mean that device that can't use exFAT can not be called SDXC compatible since it can't use the standard format (exFAT). I don't know how good that is for sales...

stefan, how do you explain this?

"as I said before, on my 8GB INOV8, class 6, SDHC card, I can only record up to 30/40 seconds of video, and then it starts buffering, and shuts the video down. "

???

thank you for all your technical jargon...