I've been looking at media prices, and there is a wide range - also people talk about quality differences and speed differences within a class.

I see the specs for class 6 as only being "above 20mbs". Are there some (class 6) cards that can't handle the 35mps data rate? How about reliability? One thing if it's DOA, but if the card is working, do some have a higher failure rate? 8^o

How about this juicy deal: PQI 16GB (SDHC) Class 6 - $26.99
PQI 16GB Secure Digital High Capacity (SDHC) Class 6 Memory Card (http://www.supermediastore.com/pqi-sdhc-16gb-secure-digital-high-capacity-memory-card.html?)
While Panasonic's 32gb SDHC 32gb at B&H is $270 (double size 10x cost!)

(not promoting either vendor - these are for comparison only)

I guess I'm looking for some discussion on relative merits of cards within the spec.

Also I think it would be useful to use this thread for user reports - add specific cards that are working seamlessly, and certainly report any that have a compatibility or other problem.

Well, I would guess what works on a EX1 should work on the JVCs too. I was planning on getting four Transcend 16GB for the HM100. I use Transcend on my still cams for years and never had a problem. The only time one card was DOA it got replaced fast and without questions asked.

I see the specs for class 6 as only being "above 20mbs". Are there some (class 6) cards that can't handle the 35mps data rate?

I think you may be confusing Megabits with Megabytes.

A Class 6 SDHC card has a minimum write speed of 6MB/sec (capital "B" for bytes), while the JVC cameras write at up to speeds of 35Mb/sec (lower-case "b" for bits).

Assuming 8 bits per byte, 35Mb/sec equals 4.375MB/sec.

Thus, any honest Class 6 card should have more than enough ceiling for the data rate, but no Class 4 card (unless it secretly exceeds the specs) can handle it.

unfortunately, the race for numbers is sometime misleading.
when some card maker claim for Classe 6, you need to check if it is peak or sustained bandwith. PQI for example is know to make cheap and bad product, claiming speed they cannot really deliver.
On the other hand, Sandisk is know to make card that perform well over their written specs.
Sandisk Ultra II, Extrem III, transcend Class 6 are known to be great products.

I've been using Sandisk and Transcend Class 6 SDHC cards and both are working well.

The best deal I've found is a Transcend 16GB + USB SDHC card reader for around $60 Canadian ($40-50 USD ?)

You can get the 16GB Transcend for $35 and free shipping from a trustworthy dealer... Not sure, if it would be okay to post the link here though, since it´s not a sponsor...

Bob - thanks for the info. I know about MB vs mb, but the 20mb speed figure I had was clearly wrong. I didn't realize the class was a the actual "minimum speed" in MB. This is supposed to be a independently verified rating.
(just went to wikipedia myself for a full explanation)
I see this also corresponds to "40x" although speed ratings in this form are often "maximum speed" It appears these well known brands exceed minimum ratings - which I assume would mean faster transfers to a hard drive as well as comfort level with full bit rate video.
That could be significant working in the field with some workflows.

Reliability is of course a real factor if it is indeed variable.

I have been using the Transcend 16 GB Class 6 card in my 700, shooting in HD and down converting to SD 4:3 via firewire ... sweet ! This card works great.

There is a lot of activity on the Sony XDCAM EX board comparing SDHC cards. They are able to use 3rd party adapters to get most functionality at a fraction of the native SxS cards (even at their new "discounted" prices).
Transcend is getting a thumbs up, and interestingly the Sandisk Ultra II's which are rated at class 4 or most recently 2 (!) have actually been shown to have good or better performance. Clearly the ratings are not always the final word in sustained performance needed for continuos video capture at HQ rate.

http://www.dvinfo.net/conf/sony-xdcam-ex-cinealta/130757-sdhc-substitute-sxs-cards.html
http://www.dvinfo.net/conf/sony-xdcam-ex-cinealta/138485-summary-sdhc-substitute-sxs-cards.html

Interestingly, I've also come up with a difference between how the Sony & JVC handle the overcranking differently. The HM700 does it as you suspect, recording at HQ 35mbps at the actual recording capture frame rate. Playback of these frames is the equivalent of a lower data rate per second - but each frame has the same data compression at the higher capture rate (eg 24/60 is the same data per frame as 60p capture).

Back to the cards - the Sony actually captures overcranking at the final playback rate. When recording 24/60, it captures a stream to make the 24fps PLAYBACK at 35mbps. This requires some 87mbps! This is where their 3rd party SDHC solution falls apart. For the hi bitrate overcranking they currently need to use the SxS media.

I'd argue that the method the Hm700 uses actually makes more sense, and the compression quality will rarely be an issue. The frames each have the same amount of data and equivalent compression as 35mbps HQ 60p footage.

Anybody used these? Delkin Devices 16GB PRO Secure Digital (SDHC) Card?

I also found out Costco has SanDisc Extreme III class 6 card (16 GB) on sale: Costco - Hot Buy SanDisk Extreme III SDHC Card 16GB (http://www.costco.com/Browse/Product.aspx?Prodid=11307826)

I use the SanDisk Ultra 2 class 4, 15MB, 16GB
What's the spec's for overcranking?


So using Bob's maths,
8 bits per byte, 35Mb/sec = 4.375MB/sec
This card is safe for normal recording but not overcranking

I use the SanDisk Ultra 2 class 4, 15MB, 16GB
What's the spec's for overcranking?


So using Bob's maths,
8 bits per byte, 35Mb/sec = 4.375MB/sec
This card is safe for normal recording but not overcranking
It doesn't matter because Class 4 cards will simply be rejected by the camera.
BTW, overcranking in the HM700 is handled as 720p60 at 35mbps no matter what frame rate is selected. The pulldown frames are then discarded and the clip is reassembled into 24p, 25p or 30p.

I have used Transcend 16 and 32 GB cards and a PNY 16 GB. They all worked fine. The PNY might be a little faster but that only matters when copying the data off.