Confused about SD and SDHC card speeds
I thought I had a decent grasp on SD cards but I am a bit confused now. I have 2 4gb SD cards. My first card, which I have been using for 6 months now is a:.

Transcend 4gb SD card 150x speed regular SD card(Not SDHC).

I just bought a second card for a good deal, it's a:.

Kingston SDHC SD4(class 4) 4gb card..

I understand class 4 in the SDHC standard means minimum of 4mbs transfer per second, but my old 150x speed SD card(Not SDHC) is way faster than that according to the specs on 150x, but I know the SDHC standard changed the block sizes a bit, which affects ultimate speed.

So my question is, I want to put the fastest/best card in my Canon S3 because I sometimes shoot video, which one would be faster/better for this since it's not necessarily and apples to apples comparison due to the changing of standards..

Can anyone clrify - Wikipedia left me confused..


Comments (5)

Firstly, video recording is actually a fairly low-speed operation (less than 2 MBps) so most any card will work just fine..

The old 150X spec usually indicated the maximum read speed of the card. Flash cards usually write at a slower speed. Fragmentation of the flash card will slow it further, hence the new Class rating. The SDHC class rating is a guaranteed minimum write speed. If your particular operations require a transfer rate of 4 MBps, then a Class 4 card is guaranteed to always meet that need, whereas with a 150X card youre never sure of how much it will slow down. The class system eliminates that uncertainty..

There are two things to understand about the Class system. First, the class system is part of the SDHC definition, so manufacturers have to give an SDHC card a class rating, and that rating must be 2,4, or 6. Second, having a class rating it doesnt limit a cards real ability...the actual minimum speeds can be higher. For example, my Transcend Class 6 4GB card will read at 18 MBps, with a minimum speed of 12 MBps..

I always recommend buying the fastest card available because youll use it in your next camera, which will probably be faster than your current camera...

Comment #1

I appreciate the response - now it's clear, but I now discovered that my choice is limited by my cameras. Was going to use the SDHC card in my Canon S3 per your recommendation, leaving the reg 4gb Sd card for my Fuji F40fx, but found out the Fuji will not read the 4gb SD card, even though the firmware has been upgraded to SDHC. So the F40 will not read a regular SD card of 4gb, Although it reads a 2gb, or a 4gb SDHC - does that make sense, as it doesn't to me...

Comment #2

Yes it makes sense. SDHC is a completely different standard than SD. SD officially has a 2GB limit. The 4GB SD cards are non-standard and may not work in some devices..

The SDHC standard uses a format that is completely incompatible with the SD standard. Devices that conform to the SDHC standard must also work with SD cards. However, all that means is that the device can work with two completely different standards...much like some DVD players will also play CDs...

Comment #3

I am not surprised you are confused. The dozy SD Association has a lot to answer for. The SDHC classes are a joke. Most fast cards exceed them by a massive margin..

4GB SD cards began to appear because the SD Assoc did not keep up. The standard could go to 4GB but stopped at 2GB so mfrds had to make treir own rules about block length etc. Hence your problem..

May people remain unaware of compatibility difficulties with SD/SDHC. Not only will many not so old card readers and devices not read SDHC but some quite modern card readers/devices will not read SD cards above 1GB! (They changed the spec along the way and if your mfr did not produce afirware update you are stuck).

SD cards have flourished in spite of the SD Association not because of them..

Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.


Comment #4

Actually, as I understand it, the spec. for SD runs out at 2GB so a 4GB SD card is really using a somewhat proprietary extension of the SD spec. Therefore having any device handle a 4GB SD card is going to be hit or miss...

Comment #5

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