......... I see 3 different 64gb Samsung SDXC cards:
EVO, PRO and UHS-1
Is one any more reliable than the others, or is it purely a matter of speed?
Is the UHS-1 the same as one of the other two?
The SD Card Association, who define the SD card designations, have explanations on site. I can't post real link yet
but it's at: sdcard.org/consumers/speed/speed_class/index.html
They say "UHS (Ultra High Speed) Speed Class is designed for UHS** devices only" and on next page "Speed Class and UHS Speed Class are two different speed indication symbols for different devices. However, a UHS-I memory card may also indicate a Speed Class. Check your manual or device to determine the right Speed Class for your device."
I've noticed SDHX cards appearing marked with both 'Speed class 10' (a 10inside a C) and with UHS class1 1(inside a U), so I'm guessing that those cards would work in both types of devices. While presumably a card having only a 1(inside a U) would not be backward compatible... {edit} from integralmemory.com: "An SDHC UHS-I card will work in any SDHC compatible device at lower speeds,"
Speed class 10 and UHS class 1 both have Minimum Serial Data Writing Speed of 10MB/s, UHS class 3 is minimum 30MB/s.
The card class defines a minimum serial write speed, so two cards in the same class could have very different performance, depending on the device. So a cards bench-mark results could differ a lot between testing in a card reader and a smart-phone.
Looking at some manufactures specifications:
For the SanDisk Ultra, maximum read speeds are up to 30 MB/s for the 64GB SDXC Class 10; up to 48MB/S for the 64GB & 128GB SDXC micro Class 10; up to 90MB/s for the 200GB SDXC micro Class 10; SanDisk Extreme microSDXC UHS-I speed U3 Read up to 60MB/s Write up to 40MB/s.
For Samsung PRO 64 GB microSDXC Card the speeds are Read: up to 70MB/s Write: up to 20MB/s, Samsung Pro+ 64GB microSDXC UHS-I U3 Read: up to 95 MB/s with UHS-1 interface Write: up to 90 MB/s with UHS-1 interface; Samsung EVO 64GB MicroSDXC U1 is up to 48 MB/s transfer speed with UHS-I interface, spec also includes "Interface UHS-I, compatible to HS interface" ... & Class 10.
I gave the the app "A1 SD bench", mentioned elsewhere in thee thread, a quick try on my Sony Z3 compact (D5803) with an old 32GB Kingston microSDHC Class 10, getting results R:25.8 MB/s W:5.97MB/s (which isn't within Class 10 spec). With an even older SanDisk microSDHC Class 4, (speed 4 spec minimum 4MB/s write) results R:20 MB/s W:4.98MB/s so that's in spec.
You can look at others results for the same model, best external SD (looking back 24 hours) was R:51MB/s W:46MB/s, so I know what the phone should good for.
It is a great pity the app doesn't read the card type and show with these results as it would be a great way of choosing the most compatible card ( perhaps if enough people add suggestion to Golgle app comments??) At least you can see what the device can achieve to know what spec is worth going for.
Write speed becomes more important if you're shooting 1080p or burst mode stills, then a Samsung Pro+ 64GB microSDXC UHS-I U3 would be usefull (& amazed by the low price) ... or wait a bit till the 128GB version comes out.