read speed is 40 MB / s
write speed (found nowhere) is 15 MB / s ...
The writing speed is important, the bigger it is, the sooner you can save files on the map
CAUTION:
The writing speed is not recommended for new HERO4 go-pro (and to my surprise the HERO3 + BLACK) which advocates for the brand Sandisk Sandisk Extreme microSDXC that rises 50m / s write (and ~ 80m / s reading) the HERO3 SILVER seems to have a lower speed and can run with the SANDISK ULTRA.
I say to my surprise because I was filming with my ultra..je BLACK + to understand better the writing and slow startup and stop recording errors (FYI it seems to write from go- pro is 45m / s so I understand better why the card was following wrong ahaha)
MODEL 128:
this model is a little apart, as are aimed quantity on other performmances
there are two versions, the original version, and put a days, so be careful that you buy has.
Sandisk card 128 old version SDSDQUA-0128G-G46A
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smartphone (mean)
Writing: 10 mb / s
Reading: 14.3 mb / s
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on pc with SD Adapter
Writing: 14 mb / s
reading: 30 mb / s (max)
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NEW VERSION SANDISK 128 UHS-I SDSDQUAN-128G-G4A CARD
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smartphone (Galaxy Note 4 - 2014 smartphone)
Writing: 17 mb / s
reading: 37 mb / s
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on pc with SD Adapter
Writing: 16.06 mb / s
Reading: 47.3 mb / s (max)
So the new version arrives almost to the characteristics of the 64 (finally)
If this comment helpful to you, thank you to note.
ps: it's hard to comment well done, and it's frustrating to have a negative vote when we think we have done our best to explain a product, so be nice first to leave a comment before, if something do not go.