user6622: I am planning to buy GoPro 4 silver edition. Since they do not come with a microSD I need to choose one. BH video recommends the below one which has 50Mb/s writing speed and costs75$. 
http://www.bhphotovideo.com/c/product/945286-REG/sandisk_sdsdqx_064g_a46a_64gb_extreme_micro_sdxc_uhs_1.html 
the one with 30Mb/s writing speed is 40$.
http://www.bhphotovideo.com/c/product/886007-REG/SanDisk_sdsdqui_064g_a11_64GB_microSDXC_Memory_Card.html
is 30Mb/s enough for me? Or should I go with the expensive one? How can I determine the required speed?
Thanks in advance.

user2836: You have to check the specification of your camera.  30Mb/s could be plenty for 60fps 4k or not enough for 24p SD, entirely depending on what format and data rate is being used.  Your camera should say the data rate of whatever you intend to record in.  Use that to determine the needed card speed.  Make sure that the write speed is actually what you need as well as read and write speeds can sometimes differ significantly on SD cards.
According to this page, the Hero4 Silver only supports 15fps 4k recording.  For that particular camera, the required data rate is 45 Mbps.  Note that memory cards are typically advertised for the READ speed which is faster than the write speed in almost all cases.  Verify that the WRITE speed exceeds 45Mbps as the camera needs to be able to catch up on writing if it falls behind.

6622: <p>I am planning to buy GoPro 4 silver edition. Since they do not come with a microSD I need to choose one. BH video recommends the below one which has 50Mb/s writing speed and costs75$. </p>

<p><a href="http://www.bhphotovideo.com/c/product/945286-REG/sandisk_sdsdqx_064g_a46a_64gb_extreme_micro_sdxc_uhs_1.html" rel="nofollow">http://www.bhphotovideo.com/c/product/945286-REG/sandisk_sdsdqx_064g_a46a_64gb_extreme_micro_sdxc_uhs_1.html</a> </p>

<p>the one with 30Mb/s writing speed is 40$.</p>

<p><a href="http://www.bhphotovideo.com/c/product/886007-REG/SanDisk_sdsdqui_064g_a11_64GB_microSDXC_Memory_Card.html" rel="nofollow">http://www.bhphotovideo.com/c/product/886007-REG/SanDisk_sdsdqui_064g_a11_64GB_microSDXC_Memory_Card.html</a></p>

<p>is 30Mb/s enough for me? Or should I go with the expensive one? How can I determine the required speed?</p>

<p>Thanks in advance.</p>
 2836: <p>You have to check the specification of your camera.  30Mb/s could be plenty for 60fps 4k or not enough for 24p SD, entirely depending on what format and data rate is being used.  Your camera should say the data rate of whatever you intend to record in.  Use that to determine the needed card speed.  Make sure that the write speed is actually what you need as well as read and write speeds can sometimes differ significantly on SD cards.</p>

<p>According to <a href="https://gopro.com/support/articles/hero4-silver-recording-time-in-each-video-setting" rel="nofollow noreferrer">this page</a>, the Hero4 Silver only supports 15fps 4k recording.  For that particular camera, the required data rate is 45 Mbps.  Note that memory cards are typically advertised for the READ speed which is faster than the write speed in almost all cases.  Verify that the WRITE speed exceeds 45Mbps as the camera needs to be able to catch up on writing if it falls behind.</p>
