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I was shopping for a couple of new memory cards for new cameras this year and noticed that there are some SD cards that are now UHS-1 compatible. I wasn't sure what that really meant so I went looking for more info, and found that UHS stands for Ultra-High Speed and brings newer, faster signaling to SD cards.

Reading the overview at Secure Digital Wikipedia page it isn't clear if the new speeds also come with a guarantee of backwards compatibility. It seems like UHS cards might be compatible if the reader/writer also accepts SDXC cards - because they were both defined in version 3.0 of the SD spec, though the signaling (voltage and actual bit transfer) is unique for UHS cards.

Anyone with hands-on experience or links to other articles/vendor pages that might shed light on the subject?

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up vote 4 down vote accepted

From Lexar's (one of bigger manufacturers of memory cards) FAQ located here:

Can I use an UHS-I card with a SDHC host device?

Yes! All SD UHS-I cards can be used with all existing SDXC and SDHC devices (backwards compatible). Note that SDXC UHS-I cards are not compatible with SD or SDHC host devices, only with SDXC host devices. See the SDXC FAQ for more information. Although SD UHS-I cards can be used with all existing SDXC and SDHC devices, if you want to optimize UHS performance, select a device with the UHS-I logo:

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Ah, so 32GB is the cutoff between SDHC and SDXC. A 32GB card will work in SDHC but not 64GB. – Chloe May 28 at 6:02

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