How much speed do you need?

A faster mem­ory card doesn’t nec­es­sar­ily make your cam­era work faster, and there’s more than one kind of ‘speed’…

NPhoto - - Over To You… -

Con­tin­u­ous shoot­ing: max­i­mum pos­si­ble speed A faster mem­ory card won’t let your Nikon shoot at a faster rate. The frame rate is fixed by the cam­era hard­ware. But the cam­era is sav­ing im­ages faster than it can write them to the mem­ory card, so it saves them tem­po­rar­ily to an in­ter­nal mem­ory ‘buf­fer’ while it’s shoot­ing. The faster the mem­ory card, the longer it takes for this buf­fer to fill up, and the quicker it can empty the buf­fer when it’s full. So a faster card will let you shoot a longer burst, and it will re­duce the de­lay be­fore the cam­era is ready to start shoot­ing again. The max­i­mum speed rat­ing of the mem­ory card is a pretty good guide to how well it’s go­ing to do this.

HD video: min­i­mum sus­tained speed

When you shoot HD video, the cam­era has to write the data straight to the mem­ory card in ‘real time’. If the min­i­mum ‘sus­tained’ speed falls be­low a cer­tain level, you get dropped frames in your footage. This is why SD/SDHC/ SDXC mem­ory cards now have a ‘Class’ rat­ing and some CF cards have VPG 20 (20MB per sec­ond, fine for am­a­teur use) and VPG 65 (65MB per sec­ond, for pros) lo­gos. A min­i­mum sus­tained speed of 10MB per sec­ond is ad­e­quate for 1920 x 1080 full HD video, while 30MB per sec­ond is needed for the new 4K video stan­dard, though no cur­rent Nikon D-SLRs shoot 4K video.

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